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Different Types of Infectious Diseases

In the wake of COVID-19, a new global understanding of infectious diseases has arisen. At the very least, the destructive capabilities of disease and its implications are now acutely felt. This view likely won’t change anytime soon, and one outcome of this pandemic could be a larger focus on individual health and medicinal sciences.

COVID-19 is a viral disease, just one of the four main types of infectious diseases. The others include bacterial, fungal, and parasitic—each different in how they spread and how they affect the body.

Let’s break these down individually to understand the types of infectious diseases.

Infectious Diseases vs Infections: Quick Definition

Before going into the four types, there’s a quick separation of terms. Infectious diseases and infections are often used interchangeably. However, there are slight distinctions between the two. An infectious disease, as defined by the Encyclopedia Britannica, is:

“A process caused by an agent, often a type of microorganism, that impairs a person’s health. In many cases, infectious disease can be spread from person to person, either directly (e.g., via skin contact) or indirectly (e.g., via contaminated food or water).”

While an infection is defined as: 

“The invasion of and replication in the body by any of various agents—including bacteria, viruses, fungi, protozoans, and worms—as well as the reaction of tissues to their presence or to the toxins that they produce.”

By these definitions, when children receive the varicella vaccine—the vaccine used to prevent chickenpox—they’re receiving an infection without producing the infectious disease.

Put simply, all infectious diseases result from an infection, but not all infections cause infectious diseases. Now that that’s in order, what are the types of infectious diseases caused by?

It All Starts With An Infectious Agent: Bacteria, Viruses, Fungi, and Parasites… oh my!

The four different categories of infectious agents are bacteria, viruses, fungi, and parasites. When studying these agents, researchers isolate them using certain characteristics:

  • Size of the infectious agent
  • Biochemical characteristics
  • Method of interaction with the human host
  • Treatment options


Bacteria are everywhere. They’re on our phone and computer screens, they’re involved in making yogurt and cheeses, and they help us digest our food. While we encounter millions of these cells every day, there are some types of bacteria that are harmful.

These are the pathogenic bacteria.

A bacterium cell is a microscopic organism that’s classified as a prokaryote. Prokaryotic cells (as opposed to eukaryotic cells) are cells with a simple internal structure and no nucleus. Though the cell has no nucleus, it does contain DNA within a nucleus-like region called the nucleoid. Because the cell structure is simpler, most bacteria reproduce rapidly—some species reproduce every few minutes.

Their size ranges from 0. 2 and 2 micrometers, on average, and they usually fall under one of three distinct shapes:

  • Cocci – Round bacteria (ex. Staphylococci – or staph infection)
  • Bacilli – Capsule-shaped bacteria (ex. Streptobacillus moniliformis – or rat bite fever)
  • Spirilla – Spiral-shaped bacteria (ex. Campylobacter jejuni – a form of food poisoning)

How Bacteria Cause Disease

Bacteria enter the human host in a variety of methods. The pathogen can physically enter through the mouth, eyes, nose, genitalia, and open wounds, and can be transmitted via airborne droplets, bodily fluids, and skin-on-skin contact.

Once bacteria enter the system, they begin to multiply rapidly. In some cases, such as with the bacteria Salmonella typhi (typhoid), the disease is caused when the bacteria die and secrete toxins that are poisonous to humans. 

In other cases, the bacteria settle in the lungs, kidney, spine, or brain and attack the tissue. Mycobacterium tuberculosis, which causes tuberculosis, grows in the lungs where it then enters the bloodstream and spreads throughout the body—attacking multiple areas of the body.

Treatment Options for a Bacterial Infection

There are two common treatment options for a bacterial infection:

  • Antibiotics – Also known as antibacterials, antibiotics suppress the serious infection by attacking the cell walls of bacteria. Once the cell wall is compromised the bacteria cells can’t survive in the human body.
  • Vaccines – Vaccines are a preventative measure that allow the body to create antibodies prior to being infected by the bacteria. These vaccines are weakened versions of the bacteria, allowing healthy immune systems to easily fight them off and become familiar with the disease.


Viral infections and bacterial infections are often confused. The main differentiator? Bacteria are living organisms, viruses are not. Instead, viruses are fragments of nucleic acid (think DNA), that are packaged together in a protein. These proteins (viruses) enter through the cell wall of a healthy individual and use the cell’s replication systems (organelles) to reproduce.

Viruses are also a degree smaller than bacteria. While bacteria are the microscopic scale, viruses are on the nanoscopic scale. 

Most viruses range between 25 nanometers, such as the poliovirus, all the way up to 250 nanometers, such as the smallpox virus.

How Viruses Cause Disease

Once a virus enters a healthy cell, it is invisible to the antibodies which circulate the bloodstream. Thus, a different mechanism is needed to identify infected cells and eliminate them. This is done with the help of the molecule: class I major histocompatibility complex proteins (MHC class 1).

MHC class 1 proteins encode the contents of the cell’s insides and then present that information externally. Part of the virus’ protein is encoded and can then be detected by T cells.

Once the T cell has identified an infected cell, it releases cytotoxic factors (cytotoxic, meaning toxic to cells) that kill the cell. The invading virus can then no longer use the cell to replicate. 

The physical symptoms of a viral infection are when the body is killing off infected cells.

Common Viruses

The seasonal flu is one of the most well-known viruses. And while the flu often sounds innocuous, its numbers are staggering. Between 2010 and 2019, the CDC estimated between 9 million and 45 million infections, as well as 12,000 to 61,000 deaths occur per year, in the US alone. 

While vaccines are available each year, the flu mutates so quickly it renders previous vaccines ineffective.

Other common viruses include:

  • Common cold
  • Norovirus
  • Stomach flu
  • Hepatitis

Treatment Options for a Viral Infection

Viruses are harder to treat than bacterial infections. This reflects how viruses operate. To kill a virus, the cell where it’s hiding has to be identified and eliminated. But no current medications can do both of these two processes simultaneously. Instead, there are two major treatment options for viruses: 

  • Antivirals – While antibacterial drugs attack and kill bacteria, antiviral drugs do not attack and kill viruses. Instead, they identify which cell is infected and then contain the virus within the cell, preventing it from reproducing. Because of its “inefficient” methodology, antivirals typically only work when there are few infected cells—it’s recommended that antiviral medications are taken 24 hours from the first sign of disease. 
  • Vaccines – The vaccines for viral infections work similar to those for bacterial infections. A weakened form of the virus is injected into the body in order to prepare the immune system to detect and fight the virus.


Fungi are typically found on dead or rotten matter (plant and animal) and exist as one of two types of cells: yeast cells or mold cells.

  • Yeast fungi – Scientists have discovered 1,500 species of these single-cell fungi. They’re found worldwide on plants, in soil, and in sugary mediums such as fruit. These fungi are the types of yeast that make bread grow and beer and wine alcoholic. Yeast cells range in size from 3 to 5 micrometers.
  • Mold fungi – Mold is made up of multicellular filaments called hyphae. These branching structures are between 2 and 10 micrometers and are found on rotting plant and animal matter.

Treatment Options For a Fungal Infection

Certain types of both yeast and mold cells are capable of causing devastating infectious diseases in people. These diseases are called mycoses, common ones being:

  • Histoplasmosis
  • Coccidioidomycosis
  • Blastomycosis

The treatment for an infected person is a combination of antibiotics and antifungals. Antifungals work similarly to antibiotics in that they attack the cell wall, causing cell death.


Parasites are living organisms that benefit from attaching to a host, at the detriment of the host itself. Common parasites include everything from malaria, which is about 4 micrometers, to tapeworms that can grow several meters in length.

One can become prone to developing a parasitic infection because parasites will often lay eggs in the host undetected. Only once the eggs hatch is when symptoms of a disease arise.

Treatment Options for a Parasitic Infection

Many treatment options are not approved by the FDA because the demand in the US for antiparasitic drugs is so low. However, the approved drug options include:

  • Artesunate
  • Diethylcarbamazine (DEC)
  • Melarsoprol
  • Nifurtimox
  • Sodium Stibogluconate (Pentostam)
  • Suramin

These drugs attempt to break down the DNA commonly found in parasitic agents.

Studying Infectious Diseases

When it comes to studying all these different types of infectious diseases, new technologies have allowed significant advancements to occur. One of these technologies? Flow cytometers.

While flow cytometry has been around for decades, traditional machines have used far too much pressure, damaging the cells in question, causing cell death and obscuring the data. 

That’s where NanoCellect’s WOLF Cell Sorter comes in. NanoCellect allows researchers to use modern flow cytometry techniques at pressures of less than 2 psi, gently isolating and sorting infected cells for further study.

It’s compact, intuitive, and it comes with disposable cartridges to avoid cross-contamination between samples.

When is comes to gentle cell sample preparation and single cell genomics —the research starts with NanoCellect



Encyclopedia Britannica. Infectious disease. https://www.britannica.com/science/infectious-disease

Live Science. What Are Bacteria? https://www.livescience.com/51641-bacteria.html

LibreTexts. 22.2B: Prokaryotic Reproduction. https://bio. libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Biology_(Boundless)

MicrobiologyInfo.com. Different Size, Shape and Arrangement of Bacterial Cells. https://microbiologyinfo.com/different-size-shape-and-arrangement-of-bacterial-cells/

British Society for Immunology. Immune responses to viruses. https://www.immunology.org/public-information/bitesized-immunology/pathogens-and-disease/immune-responses-viruses

CDC. Disease Burden of Influenza. https://www.cdc.gov/flu/about/burden/index.html

Urology of Virginia. How Viruses Work and How to Prevent and Eliminate Them Naturally. https://www.urologyofva.net/articles/category/healthy-living/4126629/how-viruses-work-and-how-to-prevent-and-eliminate-them-naturally


Encyclopedia Britannica. Yeast. https://www.britannica.com/science/yeast-fungus


CDC. Parasites – Health Professionals. https://www.cdc.gov/parasites/health_professionals. html

Types of Infectious Disease | Tampa General Hospital

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In This Section

Infectious disease is a broad term that describes an illness caused by a specific type of bacterium, parasite, virus, or fungus. Most of these organisms don’t pose a threat to health, but those that do can cause an array of illnesses, which range from mild to life-threatening. Harmful organisms can be transmitted from person to person, through animal bites, or by consuming contaminated food or water. Infectious diseases can affect anyone, although people with compromised immune systems are at a greater risk of acquiring an infection.


Here is a brief overview of the main infectious disease types:

  •     Bacterial infections – bacteria is responsible for a broad variety of infectious diseases, from strep throat and urinary tract infections to meningitis and tuberculosis. Many skin rashes are also caused by bacteria.

  •     Bone infections– an infection that affects a bone is referred to as osteomyelitis. It is most commonly caused by bacteria that enters the body through a deep wound or surgical incision, but fungi may also be to blame for a bone infection.

  •     Fungal infections – there are roughly 300 types of fungi known to cause infectious diseases. Commonly occurring fungal infections include ringworm, pneumocystis pneumonia, blastomycosis, and histoplasmosis. Localized fungal infections (such as toenail fungus) also occur frequently in the United States.

  •     Joint infections – bacterial joint inflammation, or bacterial/septic arthritis, most frequently affects the knee joint. Most cases are caused by the bacterium Staphylococcus aureus (staph), although viral or fungal infections can also cause joint infections.

  •     Tropical diseases– experienced largely by the world’s poorest populations, the most common tropical diseases include elephantiasis (lymphatic filariasis), river blindness (onchocerciasis), snail fever (schistosomiasis or bilharzia), and trachoma.

  •     Parasitic infections– the majority of parasitic infections affect countries in the tropics and subtropics, but these infections also occur in the United States. Prevalent parasitic infections include malaria, Chagas disease, and toxocariasis.

  •    Viral infections– like bacteria, viruses can cause many different infectious diseases. The common cold develops from a virus, as does more complex diseases like the flu, mononucleosis, smallpox, and HIV/AIDS.

Bacterial vs.

Viral Infections: The Differences Explained

Bacterial and viral infections have many things in common. Both types of infections are caused by microbes — bacteria and viruses, respectively — and spread by things such as:

  • Coughing and sneezing.
  • Contact with infected people, especially through kissing and sex.
  • Contact with contaminated surfaces, food, and water.
  • Contact with infected creatures, including pets, livestock, and insects such as fleas and ticks.

Microbes can also cause:

  • Acute infections, which are short-lived.
  • Chronic infections, which can last for weeks, months, or a lifetime.
  • Latent infections, which may not cause symptoms at first but can reactivate over a period of months and years.

Most importantly, bacterial and viral infections, can cause mild, moderate, and severe diseases.

Throughout history, millions of people have died of diseases such as bubonic plague or the Black Death, which is caused by Yersinia pestis bacteria, and smallpox, which is caused by the variola virus. In recent times, viral infections have been responsible for two major pandemics: the 1918-1919 “Spanish flu” epidemic that killed 20-40 million people, the ongoing HIV/AIDS epidemic that has killed almost 33 million people (as of 2019), and the Covid novel coronavirus pandemic, which has killed 3 million people as of April 2021.

Bacterial and viral infections can cause similar symptoms such as coughing and sneezing, fever, inflammation, vomiting, diarrhea, fatigue, and cramping — all of which are ways the immune system tries to rid the body of infectious organisms. But bacterial and viral infections are dissimilar in many other important respects, most of them due to the organisms’ structural differences and the way they respond to medications.

The Differences Between Bacteria and Viruses

Although bacteria and viruses are both too small to be seen without a microscope, they’re as different as giraffes and goldfish.

Bacteria are relatively complex, single-celled creatures, many with a rigid wall, and a thin, rubbery membrane surrounding the fluid inside the cell. They can reproduce on their own. Fossilized records show that bacteria have existed for about 3.5 billion years, and bacteria can survive in different environments, including extreme heat and cold, radioactive waste, and the human body.

Most bacteria are harmless, and some actually help by digesting food, destroying disease-causing microbes, fighting cancer cells, and providing essential nutrients. Fewer than 1% of bacteria cause diseases in people.

Viruses are tinier: the largest of them are smaller than the smallest bacteria. All they have is a protein coat and a core of genetic material, either RNA or DNA. Unlike bacteria, viruses can’t survive without a host. They can only reproduce by attaching themselves to cells. In most cases, they reprogram the cells to make new viruses until the cells burst and die. In other cases, they turn normal cells into malignant or cancerous cells.

Also unlike bacteria, most viruses do cause disease, and they’re quite specific about the cells they attack. For example, certain viruses attack cells in the liver, respiratory system, or blood. In some cases, viruses target bacteria.

Diagnosis of Bacterial and Viral Infections

You should consult your doctor if you think you have a bacterial or viral infection. Exceptions include the common cold, which is usually not life-threatening.

In some cases, it’s difficult to determine whether an illness is viral or bacterial because many ailments — including pneumonia, meningitis, and diarrhea — can be caused by either. But your doctor may be able to determine the cause by listening to your medical history and doing a physical exam.

If necessary, they also can order a blood or urine test to help confirm a diagnosis, or a “culture test” of tissue to identify bacteria or viruses. Occasionally, a biopsy of affected tissue may be required.


Treatment of Bacterial and Viral Infections

The discovery of antibiotics for bacterial infections is considered one of the most important breakthroughs in medical history. Unfortunately, bacteria are very adaptable, and the overuse of antibiotics has made many of them resistant to antibiotics. This has created serious problems, especially in hospital settings.

Antibiotics are not effective against viruses, and many leading organizations now recommend against using antibiotics unless there is clear evidence of a bacterial infection.

Since the beginning of the 20th century, vaccines have been developed. Vaccines have drastically reduced the number of new cases of viral diseases such as polio, measles, and chickenpox. In addition, vaccines can prevent such infections such as the flu, hepatitis A, hepatitis B, human papillomavirus (HPV), and others.

But the treatment of viral infections has proved more challenging, primarily because viruses are relatively tiny and reproduce inside cells. For some viral diseases, such as herpes simplex virus infections, HIV/AIDS, and influenza, antiviral medications have become available. But the use of antiviral medications has been associated with the development of drug-resistant microbes.

4 Types of Viral Infections and What You Can Do About Them : Health One Family Medicine: Family Medicine

Viral infections are responsible for several diseases, some of which can be fatal. Viruses are infectious agents that survive and reproduce by attaching to a host cell. Most viruses are responsible for causing a number of diseases in living things. However, some viruses such as bacteriophages can be useful. In this article, we are going to discuss common viral infections and what you can do about them.

The flu is one of the most common viral infections in the world. It is caused by the influenza virus. There are 2 types of influenza virus that cause flu epidemics every year. These are the influenza A and B viruses. There are numerous strains of these viruses, as well, and they undergo mutations every year. Symptoms of the flu include sneezing, congestion, and a sore throat. You can also develop a high fever and suffer from body aches and weakness. It is important to get plenty of rest if you get the flu. You must also maintain a high fluid intake. Pregnant women, children, and people with a weak immune system may be at greater risk and should consult a doctor. You can protect yourself from this viral disease by getting a flu vaccine.

This is another common viral disease. It is caused by the varicella-zoster virus. If you are suffering from a chickenpox infection, then red spots will appear on your body. These spots can be filled with fluid and convert into blisters. Recovering from the chickenpox infection usually takes up to 14 days. You can develop symptoms one or two days before the spots appear. These include fever, headaches, fatigue, and loss of appetite. There is no formal treatment for chickenpox. You can take acetaminophen and apply cooling creams or lotions to relieve the itching. Avoid scratching the blisters as this will leave a scar.

Acute bronchitis can be caused by both viruses and bacteria. However, the viral version of this disease is more common. Symptoms of bronchitis are similar to that of the common cold. You can also develop a cough. Treatment involves taking medicines to control the fever and treat the cough. You should also drink lots of fluids.

The human immunodeficiency virus is a virus that compromises the immune system. It is responsible for infecting and killing your T-cells. These cells help the body fight against pathogens. As a result of this virus, your body becomes vulnerable to different types of diseases. HIV can be transferred via blood, breast milk, semen, rectal fluids, and vaginal fluids. There is no cure for the HIV virus. However, you can get antiretroviral therapy. This can allow you to live with the virus for several years. If you do not opt for HIV treatment, you can get acquired immunodeficiency disease (AIDS). This disease causes your immune system to stop working altogether, which can have fatal consequences.  

There are numerous kinds of viral infections that afflict people every day. In most cases, your immune system can fight off these diseases. If you are suffering from a viral disease, then it is important to rest and keep yourself hydrated. You can also take acetaminophen. These measures can help alleviate the symptoms of most viral diseases. In some cases (such as HIV/AIDS), you can also take antiviral medicines.

If you require further advice on common viral infections, book an appointment with a physician at Health One Family Medicine.

Visit https://www.healthonemedicine.com or call 469-208-9770 for more information.


Health One Family Medicine

How many different types of infection are there? Professor Hallux finds out in Hallux’s Kaleidoscopic Antibiotic podcast for kids! – Fun Kids

The human body is full of microbes – tiny living organisms that are found pretty much everywhere on Earth but are too small to be seen with the naked eye!

There are five main types of microbes. Three of the most common are:

Viruses – the smallest of the microbes and are generally harmful to us, like the common cold. Viruses cannot survive by themselves and require a ‘host’ cell in which to live and reproduce. Once inside that host cell, they rapidly multiply destroying the cell in the process – yuck!

Bacteria – single celled organisms that under the right conditions can multiply on average once every 20 minutes! Some bacteria are completely harmless to us and others are extremely useful (like Lactobacillus in the food industry).  Some bacteria though can also produce substances (toxins) which are extremely harmful to us and cause disease (like pneumonia). Harmless bacteria are called non-pathogenic, while harmful bacteria are known as pathogenic. Over 70% of bacteria are non-pathogenic.

Fungi – generally multi-cellular organisms that can be both beneficial and harmful, causing things like athlete’s foot!. Fungi obtain their food by either decomposing dead organic matter or by living as parasites.  They range in size from being microscopic to very large and include mould, mushrooms and mildew! Harmful fungi can cause an infection and some are poisonous to eat; others can be beneficial.

Most microbes cause no harm to the human body and many help keep you alive, so it’s important to look after them. Some, though, can be harmful and can cause infections…

Professor Hallux and Nurse Nanobot are charge up the Helitelibubble, Hallux’s amazing invention that can shrink people to the size of an atom. They’re going to fifty nanometers, fifteen hundred times smaller than a human hair is wide, to explore the human body!

Click here to find out more about your body!

First up, they come across a STREPTOCOCCUS! That’s a type of bacteria! They are single cell organisms which often grow in communities.

STREPTOCOCCI are responsible for a large majority of problems in the mouth – from throat infections to tooth decay.

Click here to find out more about your body!

As well as Streptococci, there’s lots of other different types of bacteria. In fact, there’s SO many, we can’t keep up! The numbers have gone off the scale – there’s millions of bacteria in your our mouths.

Of course, many microbes, most bacteria are nothing to worry about. Most are entirely harmless, and some are even extremely useful to us!

LACTOBACILLUS helps turn milk into yoghurt and helps food to be digested, whilst BACTEROIDES help bodies make important vitamins!

RHINOVIRUS cause the common cold.

Click here to find out more about your body!

Each individual virus looks like a bobbly ball and they’re very small indeed. Only 30 nanometres wide – you could fit over thirty thousand of them on a full stop!

There’s over 200 types of rhinovirus, which is probably why the common cold is – well – so common!

Did you know that the word ‘virus’ comes from a Latin word which means SLIMY LIQUID or POISON!?

Viruses are some of the very smallest microbes. They work by invading a cell and forcing it to create thousands of copies of the virus.

But don’t worry, with some rest and maybe some medicine, you’ll be feeling normal in no time!

Activities for you to do

Activity 1: Why don’t you have a god at creating your own microbial collage by getting an A3 piece of paper, a selection of magazines and cut and stick anything you find in the magazines which may contain/have microbes on it!

Activity 2: Or have a go at creating your own microbe out of playdoh or plasticine.  Be as creative as you want and keep your creation in a plastic container so that it does not escape and cause an outbreak!

Activity 3: Or you could battle against the computer on this Microbe Mayhem card game. Choose the category on your card (e.g max size, danger to humans) that you think will beat the computer’s card. Win by stealing all the computer’s cards!

And for teachers

Introduction to microbes: Primary / Secondary
Useful microbes: Primary / Secondary
Harmful microbes: Primary / Secondary

Click here to find out more about your body!

  1. There are different types of microbes (bacteria, viruses, fungi)
  2. Bacteria, viruses and fungi look and function very differently.
  3. Most microbes in the body are useful, so we need to look after them.
  4. Some Microbes we pick up/catch from others, and things we touch and eat can be harmful to the human body.
  5. Harmful microbes can cause infections!

Learn about the human body in this podcast – from brains and bones to ears and eyes!


Learn about the human body in this podcast – from brains and bones to ears and eyes!

Professor Hallux’s Antibiotics, supported by e-Bug and Public Health England.

Explore all the free Fun Kids podcasts!

Download a series to listen to on your phone, tablet or in the car!


Infectious Diseases: Symptoms, Causes, Treatments


What are infectious diseases?

Infectious diseases can be caused by many pathogens, including bacteria, viruses, fungi, and parasites that may cause illness and disease. For humans, transmission of pathogens may occur in a variety of ways: spread from person-to-person by direct contact, water or foodborne illness or aerosolization of infected particles in the environment and through insects (mosquitoes) and ticks.

Signs and symptoms and treatment of infectious diseases depend on the host and the pathogen.

Who is most at risk for getting infectious diseases?

Anyone can get an infectious disease. People with a compromised immune system (an immune system that doesn’t work at full strength) have greater risk for certain types of infections. Those at higher risk include:

  • People with suppressed immune systems, such as those going through cancer treatment or who have recently had an organ transplant
  • Those who are unvaccinated against common infectious diseases
  • Healthcare workers
  • People traveling to at-risk areas where they may be exposed to mosquitoes that carry pathogens such as malaria, dengue virus and Zika viruses.

How common are infectious diseases?

Infectious diseases are extremely common worldwide. Some infectious diseases strike more often than others. For instance, in the United States, 1 out of every 5 people is infected with the influenza (flu) virus each year.

What complications are associated with infectious diseases?

Many infectious diseases cause complications. These can range from mild to severe. For some conditions, complications may include wheezing, skin rash, or extreme fatigue. Mild complications usually disappear as the infection resolves.

Certain infectious diseases may cause cancer. These include hepatitis B and C (liver cancer), and human papillomavirus (HPV) (cervical cancer).

Symptoms and Causes

What are the symptoms of infectious diseases?

Symptoms of infectious disease are particular to the type of disease. For example, symptoms of influenza include:

Other infectious diseases, such as Shigella, cause more serious symptoms, including:

  • Bloody diarrhea
  • Vomiting
  • Fever
  • Dehydration (lack of fluid)
  • Shock

You may experience one or several symptoms of an infectious disease. It’s important to see a doctor if you have any chronic (ongoing) symptoms or symptoms that get worse over time.

What causes infectious diseases?

Infectious diseases in humans are caused by microorganisms including:

  • Viruses that invade and multiply inside healthy cells
  • Bacteria, or small, single-celled organisms capable of causing disease
  • Fungi, which include many different kinds of fungus
  • Parasites, which are organisms that live inside host bodies causing sickness

Infectious diseases spread in multiple ways. In many cases, direct contact with a sick individual, either by skin-to-skin contact (including sexual contact) or by touching something another person touches, transmits the disease into a new host. Contact with body fluids, such as blood and saliva, also spreads infectious diseases.

Some diseases spread through droplets discharged from a sick person’s body when they cough or sneeze. These droplets linger in the air for a short period of time, landing on a healthy person’s skin or inhaled into their lungs.

In some cases, infectious diseases travel through the air for long periods of time in small particles. Healthy people inhale these particles and later become sick. Only certain diseases spread with airborne transmission, including tuberculosis and the rubella virus.

Diagnosis and Tests

How are infectious diseases diagnosed?

Doctors diagnose infectious diseases using a variety of laboratory tests. Samples of blood, urine, stool, mucus or other body fluids are examined and provide information used in the diagnostic process.

In some cases, doctors identify infectious organisms by examining them under a microscope. Occasionally, laboratories must grow, or culture, the infectious organism from a sample to confirm its presence.

Management and Treatment

How are infectious diseases treated?

Treatment depends on which microorganism causes the infection.

  • If bacteria cause a disease, treatment with antibiotics usually kills the bacteria and ends the infection.
  • Viral infections are usually treated with supportive therapies, like rest and increased fluid intake. Sometimes people benefit from antiviral medications like oseltamivir phosphate (Tamiflu®).
  • Doctors treat fungal and parasitic infections with antifungal medications, like fluconazole (Diflucan®), and antiparasitic drugs, such as mebendazole (Emverm®).

In all cases, doctors treat specific symptoms of infectious diseases according to the latest medical guidelines. Talk with your doctor about your symptoms to explore possible treatment options.


Can infectious diseases be prevented?

Vaccines are available to prevent many common infectious diseases, including hepatitis, diphtheria, influenza and herpes zoster. The CDC has updated recommendations for vaccinations for children, adolescents and adults. There are new platforms for delivery of vaccinations and research on new pathogens. It is also important to consult with a travel clinic prior to travel overseas to be sure you are protected.

You can also reduce your risk of contracting an infectious disease by:

  • Washing your hands with soap and water, thoroughly and frequently
  • Covering your nose and mouth when you sneeze or cough
  • Disinfecting frequently touched surfaces in your home and workplace
  • Avoiding contact with sick people or sharing personal items with them
  • Not drinking or swimming in contaminated water supplies
  • Not eating or drinking food and beverages prepared by people who are sick

Outlook / Prognosis

What are the outcomes after treatment for infectious diseases?

With treatment, most people recover fully from infectious diseases. Some infectious diseases, like HIV (human immunodeficiency virus), cannot be cured yet. Instead, doctors focus on symptom management and preventing the disease from progressing further.

Increasingly, antibiotic medications may not be effective against certain infectious diseases. Gonorrhea, a sexually transmitted infection affecting both men and women, is usually treated with antibiotics. Recently, doctors have identified drug-resistant strains of the bacteria that causes gonorrhea. These resistant strains are much less likely to respond to treatment with antibiotics. It’s important to seek care from a doctor who can help you find the right therapy for a persistent infection.

Living With

When should I call my doctor concerning an infectious disease?

Let your doctor know if you have any symptoms of an infectious disease, especially if they are unusual or don’t go away over time. Symptoms like fever, vomiting and diarrhea may lead to more serious complications, including dehydration.

Your doctor should also know if you plan to travel to foreign countries. You may need to be vaccinated against common infectious diseases occurring at your destination.

If you have an ongoing infection, frequent follow-ups with your doctor help ensure your condition does not worsen.

Types of infections | Coping physically

Viruses are tiny particles that can’t live on their own. To reproduce, they need to infect a living cell, such as a cell in a human body.

It’s a virus that causes flu. The most common types of viruses that cause infections in people with cancer include some of the following.

Common cold viruses

Common cold viruses occur often in healthy people and do not usually cause major problems. But these viruses can cause serious infections, such as pneumonia, if your immune system is weak. You should try to stay away from people with colds if you’re having cancer treatment that weakens your immune system, though this might seem difficult.

Herpes simplex

Herpes simplex is a virus that causes cold sores and genital herpes.

These infections are usually mild when you have a healthy immune system. But the virus can cause serious infections for people with a weakened immune systems, including some people with cancer.

Varicella zoster

Varicella zoster is related to the herpes simplex virus. Varicella zoster is the same virus that causes chicken pox. It can cause very serious and sometimes fatal infections, such as pneumonia, in people with cancer.

The virus also causes a painful condition called shingles. You can only get shingles if you have had chicken pox in the past. This is because after you’ve had chicken pox the virus does not fully go away. It lies inactive in the body, but can become active again if the immune system is weak.

This is why people can get shingles after chemotherapy treatment.

Cytomegalovirus (CMV)

Cytomegalovirus (CMV) is common and can cause several types of infections.

Cytomegalo just means large cell, which is how the infected cells look under a microscope (swollen and big). Most people will have had a CMV infection by the time they are adults.

It isn’t generally serious. But the virus can remain inactive in your body for many years and cause recurrent infections.

This usually only becomes a problem in people who have very weakened immune systems. For example, it can cause serious chest infections after a stem cell or bone marrow transplant.

Flu (influenza)

Flu is an infection caused by viruses. It’s very infectious. You mainly catch it from coughs and sneezes of people who have a flu virus.

When you have flu you feel unwell more quickly than with a cold. Flu often causes:

  • high temperatures (fever)
  • aching muscles
  • coughing
  • headaches

Many cancer treatments can affect the immune system, so you’re less able to fight infections. It will take you longer to recover from flu if you do get it. And you’re more likely to develop complications such as chest infections.

Your doctor might suggest you have the flu jab and will tell you how and when to get it.

90,000 Children’s infections – types, descriptions, differences and features

Children’s diseases are a whole category of medicine, which includes a number of infectious diseases that are unique to childhood. However, this limitation does not provide any guarantee that the disease will not occur in adulthood. Modern medicine recommends following mandatory vaccination measures, although many parents still refuse to give them to their children. What childhood infections are known, and how do they threaten young patients?

Types of children’s infections

All children’s infectious diseases are transmitted by contact with a sick patient by airborne droplets or by household contact. In some cases, the baby may not be infected because the antibodies were passed on from the mother. Children’s infections include:

  • Scarlet fever.
  • Rubella.
  • Measles.
  • Chickenpox.
  • Poliomyelitis.
  • Whooping cough.
  • Viral parotitis (mumps).

Diseases such as acute respiratory infections, intestinal infections, meningitis, mononucleosis are also often recorded in childhood. But they are often found in adults, so it is inappropriate to classify them as childhood infections.


Measles is a highly infectious infection. The infectious agent spreads with the air stream, while it does not quickly die in the external environment. The incubation period is on average 20 days. The initial symptoms are very similar to those of a common cold, and around the 4th day, a rash appears that spreads throughout the body. Even on the mucous membranes in the mouth, small-point formations are observed.

The temperature with measles lasts until the rash disappears.But it is important to understand that this is a very serious disease for the child’s immune system, therefore, after measles, bronchitis, otitis media and even pneumonia are often observed.

Viral mumps

The infection is spread by airborne droplets. The incubation period lasts from 7 to 20 days. The first symptoms include the appearance of headaches, which is not surprising, since with this disease the nervous system suffers, and the temperature is high up to 39 degrees. The infection also affects the pancreas, and in boys the testicles, therefore, male infertility is often diagnosed after a disease in adulthood.

The disease is very serious, it can be complicated by meningitis, so it is important not to give up the vaccine and at the first sign of the disease see a doctor.

Scarlet fever

The infection is of a streptococcal nature, is characterized by high infectiousness, and practically no incubation period. The child develops a sore throat, vomiting, fever, and a small-point rash is localized mainly on the abdomen, cheeks, armpits, groin.


The causative agent of the disease is diphtheria bacillus, and the child becomes infected by its negative effect on the tonsils. Symptoms appear on average 10 days after infection, the main one is considered to be gray plaque on the tonsils – it distinguishes the disease from sore throat. Diphtheria is dangerous for the life of a child, so you should not refuse the DPT vaccination, because it was she who turned this disease into a rare infection.


Very easily transmitted, incubation period from 7 to 21 days.The disease is easily treated, and it is characterized by a blistering rash. Almost everyone can tolerate chickenpox.


This is a viral infection, the incubation period of which can be up to 30 days, although in reality it is much shorter. Symptoms of infection can be called classic for a viral lesion, but there is still one difference – pain in the limbs. Vaccinations are essential to prevent infection.


The infection has many similarities to measles – the same rash and fever.But there is one difference – with rubella, the lymph nodes become inflamed, but it is much easier to tolerate, and the rash goes away earlier.

Infectious diseases should only be treated by a doctor. Considering that many childhood infections have common features, and the onset of the disease is almost always the same, you cannot do without a specialist. Self-medication of children can lead to undesirable or negative consequences, as well as the choice of a poor quality doctor. That is why you should use the services of only qualified professionals with work experience.

Sexually transmitted infections (STIs)

More than 30 different bacteria, viruses and parasites are known to be transmitted sexually. The highest incidence rates of STIs are associated with eight of these pathogens. Four of these eight infections – syphilis, gonorrhea, chlamydia, and trichomoniasis – are currently curable. The other four infections are viral and untreated – hepatitis B, herpes simplex virus (HSV, or herpes), HIV, and human papillomavirus (HPV).The severity of symptoms or illness caused by refractory viral infections can be alleviated or altered with therapy.

STIs are transmitted primarily through sexual contact, including vaginal, anal and oral sex. In addition, a number of STIs are transmitted asexually, such as through blood or blood products. Many STIs, including chlamydia, gonorrhea and mainly hepatitis B, HIV and syphilis, can also be passed from mother to child during pregnancy and childbirth.

STIs can occur without obvious symptoms of the disease. Common symptoms of STIs include vaginal discharge, urethral discharge or burning sensation when urinating in men, genital ulcers, and abdominal pain.

The magnitude of the problem

STIs have profound negative impacts on sexual and reproductive health around the world.

More than one million STI infections occur every day. According to WHO estimates, in 2016there were 376 million cases of one in four STIs – chlamydia (127 million), gonorrhea (87 million), syphilis (6.3 million) or trichomoniasis (156 million). More than 500 million people are living with genital HSV (genital herpes) infection, and about 300 million women are infected with HPV, the leading cause of cervical cancer. An estimated 240 million people worldwide are living with chronic hepatitis B. Infection with HPV and the hepatitis B virus can be prevented through vaccination.

STIs can have serious consequences beyond the direct effects of the infection itself.

  • STIs such as herpes and syphilis can increase the risk of HIV infection by three or more times.
  • Mother-to-child transmission of STIs can result in stillbirth, neonatal death, low birth weight and prematurity, sepsis, pneumonia, neonatal conjunctivitis and congenital anomalies. It is estimated that in 2016, about 1 million pregnant women were infected with syphilis, leading to approximately 350,000 adverse births, of which 200,000 were stillbirths and neonatal deaths (5).
  • HPV infection causes 570,000 cases of cervical cancer annually and more than 300,000 deaths from cervical cancer (6).
  • STIs such as gonorrhea and chlamydia are the main causes of pelvic inflammatory disease and infertility in women.

Prevention of STIs

Counseling and Behavior-Based Approaches

Counseling and behavior change interventions are a means of primary prevention of STIs (including HIV) as well as preventing unwanted pregnancies.These include, inter alia:

  • Comprehensive sexuality education, pre- and post-test STI and HIV counseling;
  • Safer sex / risk reduction counseling, condom promotion;
  • Interventions targeting key and vulnerable populations such as adolescents, sex workers, men who have sex with men and people who inject drugs;
  • Education and counseling tailored to the needs of adolescents.

In addition, counseling can improve people’s ability to recognize STI symptoms and the likelihood that they will seek medical attention or recommend to their sexual partners. Unfortunately, public ignorance, lack of training among health workers, and persistent and widespread stigmatization of everything related to STIs continue to hinder wider and more effective use of these interventions.

Barrier methods

When used correctly and consistently, condoms are one of the most effective methods of protection against STIs, including HIV. Female condoms are effective and safe, but are not used as widely in national programs as male condoms.

STI Diagnosis

Accurate STI diagnostic tests are widely used in high-income countries. They are of particular interest for the diagnosis of asymptomatic infections.However, the availability of diagnostic tests in low- and middle-income countries remains very low. In countries where tests are available, they are often prohibitively expensive and not available locally; at the same time, patients often have to wait too long for the results (or return to the diagnostic institution for them). As a result, follow-up monitoring becomes difficult, and medical assistance or treatment is not provided in full.

Syphilis and HIV tests are currently the only inexpensive rapid STI tests.A rapid syphilis test is already being used in some resource-limited countries. A rapid parallel HIV / syphilis test is also available today, in which only one finger stick sample is taken and a simple test cartridge is used. This test is reliable, gives results in 15-20 minutes and can be used with minimal training. With the advent of rapid tests for syphilis, diagnostic rates for pregnant women have increased. However, in most low- and middle-income countries, additional efforts are still needed to ensure that all pregnant women are tested for syphilis.

A number of rapid tests for other STIs are being developed to improve the diagnosis and treatment of STIs, especially in resource-limited settings.

STI treatment

There are currently effective treatments for some STIs.

  • Three bacterial STIs (chlamydia, gonorrhea and syphilis) and one parasitic STI (trichomoniasis) are usually treatable with effective single-dose antibiotic regimens available.
  • For herpes and HIV, the most effective medications available are antiretrovirals, which can alleviate the disease without providing a complete cure.
  • For hepatitis B, there are immunomodulators (interferon) and antiretroviral drugs that help fight the virus and slow the destruction of the liver.

Antibiotic resistance of STIs, in particular gonorrhea, has grown rapidly in recent years, narrowing the range of treatment options. The Gonococcal AMR Surveillance Program (GASP) has identified high rates of quinolone resistance, increasing resistance to azithromycin, and emerging resistance to extended-spectrum cephalosporins, the last-line drugs.The appearance of a reduced sensitivity of the causative agent of gonorrhea to extended spectrum cephalosporins, along with the already existing resistance to penicillins, sulfamides, tetracyclines, quinolones and macrolides, puts gonococcus in a number of microorganisms with multidrug resistance. Antimicrobial resistance of other STIs also exists, although it remains less common, making STI prevention and early treatment critical (7).

STI case management

In low- and middle-income countries, treatment is based on identifying persistent, easily recognizable signs and symptoms without laboratory testing. This approach is called syndrome-based. Syndrome therapy, often based on clinical algorithms, allows healthcare professionals to diagnose a specific infection based on observed syndromes (such as vaginal discharge, urethral discharge, genital ulcers, abdominal pain).

Syndromic therapy is a simple technique that provides quick treatment on the same day as medical care, and eliminates the need to perform expensive or difficult-to-find diagnostics of patients with symptomatic disease. However, this approach may lead to unnecessary treatment and missed infections, since most STIs are asymptomatic. Thus, it is imperative that post-syndromic therapy is accompanied by screening.

To prevent the spread of infection and prevent relapse, an important part of the treatment of patients with STIs is the treatment of their sexual partners.

Vaccines and other biomedical interventions

There are safe and highly effective vaccines for two STIs – hepatitis B and human papillomavirus (HPV). Their appearance was a great achievement in the field of STI prevention. In 95% of countries, the hepatitis B vaccine is included in the childhood immunization schedule, which prevents millions of deaths from chronic liver disease and liver cancer every year.

As of October 2018, HPV vaccination is included in the immunization schedule in 85 countries, most of which are high and middle income countries. Achieving high (> 80%) coverage of young women (ages 11-15) with HPV vaccines would prevent millions of female deaths over the next decade in low- and middle-income countries with the highest incidence of cervical cancer …

The work on obtaining vaccines against herpes and HIV is close to completion, and a number of candidate vaccines are already in the first stages of clinical trials. Work on vaccines against chlamydia, gonorrhea, syphilis and trichomoniasis is still in its early stages.

Other biomedical interventions for the prevention of some STIs include adult male circumcision and the use of microbiocides.

  • Male circumcision reduces the risk of HIV infection among heterosexual men by about 60% and provides some protection against other STIs such as herpes and HPV.
  • The use of a gel containing tenofovir as a vaginal microbiocidal agent has had mixed results in preventing HIV transmission, but has shown some efficacy against HSV-2.

Current STI containment measures are not enough

Behavior change is challenging

Despite significant efforts to identify simple interventions that can reduce risky sexual behavior, behavior change remains challenging.Research has highlighted the need to target carefully defined populations, extensively consult with identified target populations and involve them in the design, implementation and evaluation of interventions.

STI screening and treatment services are still underdeveloped

People seeking STI screening and treatment services face many challenges. These constraints include limited resources, stigmatization, poor quality of services, and little or no follow-up to sexual partners.

  • In many countries, STI services are provided separately and are not integrated into primary health care, family planning and other routine health care.
  • In many settings, screening for asymptomatic infections is often not possible due to a lack of trained personnel, laboratory capacity and appropriate medication.
  • The marginalized populations with the highest rates of STIs, such as sex workers, men who have sex with men, people who inject drugs, prisoners, mobile populations and adolescents, often lack access to adequate sexual services. health.

WHO work

WHO develops global norms and standards for STI treatment and prevention, strengthens surveillance and monitoring systems, including for drug-resistant gonorrhea, and leads the global STI research agenda.

Our work is currently guided by the Global Health Sector Strategy on Sexually Transmitted Infections 2016–2021. ”(8) , adopted by the World Health Assembly in 2016, and the Global Strategy for Women’s, Children’s and Adolescent Health (9), adopted by the United Nations in 2015, which emphasize the need to provide a comprehensive, integrated package of essential interventions, including the provision of information and services for the prevention of HIV and other sexually transmitted infections. The Sixty-ninth World Health Assembly adopted three global health sector strategies for the period 2016–2021.for HIV, viral hepatitis and sexually transmitted infections (STIs).

WHO is working with countries to address the following challenges:

    • STI case management and STI counseling;
    • testing for syphilis and its treatment, especially among pregnant women;
    • vaccination against hepatitis B and HPV;
    • screening for STIs in populations at high risk of STIs;
    • Integration of STI services into existing health systems;
    • sexual health promotion;
    • STI burden measurement;
    • STI antimicrobial resistance monitoring and response;
    • point-of-care STI diagnostics tests;
    • new drugs for gonorrhea;
    • STI vaccines and other biomedical interventions.

The most dangerous infections in the history of mankind – Biographies and information

TASS-DOSSIER. As of January 24, 2020, the number of confirmed cases of pneumonia in China caused by a new type of coronavirus 2019-nCoV has reached 900. Cases of infection have also been recorded in Vietnam, Thailand, the Republic of Korea, the United States, Singapore and Japan.

Information on the most dangerous infectious diseases – in the material TASS.


Plague (or plague disease) is an infectious disease caused by the plague bacillus bacterium (lat.Yersinia Pestis; discovered in 1894), found on small animals (rodents) and on the parasites living on them – fleas. It is transmitted to humans through the bite of an infected flea, through direct contact with infected materials, or by airborne droplets from a sick person. The incubation period is 3-7 days, then symptoms typical of influenza develop: a sudden rise in temperature, chills, headache and body aches, as well as weakness, nausea and vomiting. There are three forms of plague. In bubonic, the most common form, the plague bacillus attacks the lymphatic system.As a result, the lymph node becomes hard, a bubo appears on the body. In the late stage of the disease, the inflamed lymph nodes turn into festering wounds. In the septic form, the infection penetrates through cracks in the skin and enters the bloodstream immediately. Pneumonic plague, the most severe and least common form of plague, is associated with respiratory damage. If untreated, the disease can lead to serious complications and death (mortality – 30% -60%). In the fight against plague, antibiotic treatment is effective, as well as supportive therapy.If untreated, the disease can be fatal in a short time.

The first information about a disease with similar symptoms dates back to the times of Ancient Rome. However, it is believed that it had spread in an earlier period in the territory of modern Libya, Syria and Egypt. Plague has caused widespread pandemics in the past. In the XIV century. one of the forms of plague, better known as the “black death”, according to some sources, claimed the lives of 50 million people. According to the World Health Organization (WHO), 3,000 people were registered in 2010-2015.248 cases of plague of various forms, 584 people died from the disease.


Smallpox is caused by the Variola virus (Latin Variola). It is transmitted by airborne droplets, as well as through objects with which the infected person has come into contact. The incubation period is 7-17 days. The disease begins with a sharp increase in temperature, headache, often nausea and vomiting. After 2-3 days, the temperature drops, a nodular-bubble rash appears on the skin and mucous membranes, leaving behind scars (pockmarks).In 30% of cases, a lethal outcome is observed, in rare forms (confluent, hemorrhagic, purple) mortality reaches 70% or more.

Until recently, it was believed that smallpox appeared in Africa or Asia in the 4th millennium BC. NS. However, scientists today suggest that the human virus is close to the camelpox virus and passed to humans in the Middle East region at the beginning of our era. The smallpox epidemic first swept across China in the 4th century, in the 6th century. struck Korea. In the VIII century. the disease was introduced to Europe (in the 17th-18th centuries.epidemics covered almost the entire population of Europe, annually more than 1.5 million people died from this disease; in Russia, this disease reached its highest spread in the 18th century). By the beginning of the XVI century. the first mention of smallpox in America, where it could have been brought by the Spanish conquerors. At the end of the 18th century. smallpox was introduced to Australia.

It was possible to cope with the disease thanks to the WHO global vaccination program, which has been implemented since the second half of the 1960s. The last human case of smallpox was recorded on October 26, 1977 in Somalia.The victory over the disease was officially announced in 1980. Only two laboratories have the right to store the virus and conduct research – the Russian State Research Center for Virology and Biotechnology “Vector” (the village of Koltsovo, Novosibirsk region) and the American Center for Disease Control and Prevention (Atlanta, Georgia).


Cholera is an acute intestinal infection caused by bacteria of the Vibrio cholerae species, characterized by damage to the gastrointestinal tract, impaired water-salt metabolism and dehydration.It spreads through contaminated water and food, and is closely linked to poor sanitation and a shortage of clean drinking water. Cholera has been known since ancient times until the middle of the 20th century. remained one of the most dangerous epidemic diseases. In the XIX century. cholera has spread from its original reservoir in the Ganges delta in India throughout the world. Six consecutive pandemics have claimed the lives of several million people around the world. The seventh epidemic began in 1961 in South Asia and spread to Africa in 1971 and America in 1991. Currently, isolated cases and outbreaks of the disease occur in developing and poor countries, especially during massive natural disasters. So, after the devastating earthquake in Haiti in January 2010, the number of victims of an outbreak of cholera exceeded 7.5 thousand. In January 2011, cholera from Haiti was transferred to Venezuela, the Dominican Republic, Spain, the United States and Mexico, in 2012 – to Cuba.

According to the WHO, from 3 million to 5 million cases of cholera occur annually, of which more than 100 thousand are- fatal. Two types of vaccines are used to prevent this disease. They provide sustained protection of over 50% for two years.

“Swine flu”

“Swine Influenza” is a conventional name for a viral infectious disease in humans that originally spread among domestic pigs (in 2009 in Mexico and the United States). The virus is transmitted by household and airborne droplets and causes symptoms typical of influenza and SARS – cough, headache, fever, vomiting, diarrhea, runny nose. The most dangerous complications are pneumonia. “Swine flu” is one of the most common influenza type A and includes the subtypes h2N1 (most common), h2N2, h4N1, h4N2 and h3N3. The most reliable way to avoid getting swine flu is to get the seasonal vaccine.

In 1957-1958, the h3N2 virus led to a pandemic, then from 20% to 50% of the world’s population fell ill and from 1 million to 4 million people died, while most often the flu affected children. Another pathogen, the h4N2 virus, caused an epidemic of 1968-1969, the first cases of which were recorded in Hong Kong.The disease spread throughout the world has claimed the lives of up to 4 million people. A significant outbreak of the h2N1 virus occurred in 2009-2010. According to WHO, then the pandemic covered 30% of the world’s population in 214 countries, more than 18 thousand people died.

It is believed that one of the types of “swine flu” was the so-called. Spanish flu – an epidemic of 1918-1919 that spread around the world from Spain. Then more than 500 million people fell ill, from 20 million to 50 million died. This is the most massive pandemic in terms of the number of deaths in the history of mankind.


Ebola virus disease (EVD) affects humans and certain animal species. The virus was first recorded in 1976 in Zaire (now the Democratic Republic of the Congo, DR Congo), in a village on the banks of the Ebola River, which is why it got its name. It is believed that bats were originally carriers of the virus. It is transmitted to humans from wild animals and spreads from person to person through close contact through mucous membranes or skin lesions.The disease manifests itself with fever, jaundice, hemorrhagic syndrome, and renal failure. The incubation period ranges from 2 to 21 days. During outbreaks of the disease, the mortality rate reaches 90%. Experts identify five types of the virus: Bundibugio (BDBV), Zaire (EBOV), Sudan (SUDV), Tai Forest (TAFV), Reston (RESTV; affects only animals).

Outbreaks of fever were reported in the DR Congo in 1976, 1995 and 2007, in the Sudan in 1976, in Uganda in 2000 and in the Republic of the Congo in 2003.The greatest number of lives was claimed by the epidemic in 2013-2016, which covered Guinea, Sierra Leone and Liberia. Cases have also been reported in Mali, Nigeria, Senegal, Spain, Great Britain, Italy and the United States. According to the WHO, since the beginning of this epidemic, about 30 thousand people have been infected, 11.3 thousand people have died. In 2018-2019, outbreaks of the epidemic took place intermittently in the DR Congo (3.4 thousand cases, 2.3 thousand deaths).


Acquired Immunodeficiency Syndrome (AIDS) is a disease that develops when infected with the Human Immunodeficiency Virus (HIV).The virus attacks the immune system and weakens the body’s defenses against infection and disease. HIV can be transmitted through sexual contact, contaminated blood transfusions, the use of contaminated needles or sharp instruments, and from mother to child during pregnancy, childbirth and breastfeeding. AIDS can develop 2-15 years after infection. There is no cure for HIV infection. However, treatment with antiretroviral drugs can control the virus, prevent transmission, and reduce the damaging effects on the body.

Some scientists believe that HIV was passed from monkeys to humans as early as the 1920s. The first victim of this disease, presumably, was a man who died in Congo in 1959 (the doctors came to this conclusion after analyzing his medical history later). For the first time, the symptoms of the disease characteristic of HIV infection were described in June 1981 in the United States. In 1983, researchers from the United States and France described a virus that can cause HIV / AIDS.

According to the Joint United Nations Program on HIV / AIDS, in 2018 there were about 37.9 million people living with HIV in the world, of which 1.7 million were children under the age of 15.The most unfavorable region is the countries of Eastern and Southern Africa, where about 20. 6 million people are infected. The number of new HIV infections decreased by 40% compared to 1997, when this indicator peaked, from 2.9 million to 1.7 million. In Russia, from 1987, when the first case of the disease was detected, to June 30 In 2019, 1.38 million HIV infections were registered among citizens of the Russian Federation, of which 335 thousand 867 people died.


Coronaviruses are virus species belonging to the Coronavirinae subfamily of the Coronaviridae family (order Nidovirales).First discovered in the 1960s, they are the cause of gastrointestinal and respiratory infections in both humans and animals. There are 39 coronaviruses, including Severe Acute Respiratory Syndrome and Middle East Respiratory Syndrome viruses.

Severe Acute Respiratory Syndrome (SARS), also known as SARS, is an acute infectious respiratory disease that progresses rapidly and has a death rate of about 10%.The incubation period (the interval between infection and the onset of symptoms) is usually up to 10 days. The disease begins with a rise in temperature (over 38 degrees Celsius), fever, chills, headache and muscle pain. After 3-7 days, the phase of deterioration of the respiratory system begins. The disease spreads by airborne droplets and by household contact.

The SARS outbreak was first reported in November 2002 in the southern China province of Guangdong.Subsequently, numerous cases of the disease were recorded in China, Vietnam, New Zealand, Indonesia, Thailand and the Philippines. In addition to Asian countries, SARS has been reported in North America and Europe. In Russia, only one case of the disease was recorded (the patient was cured). According to WHO, during the epidemic in 2002-2003, the total number of cases in 37 countries of the world reached 8,437 people, of which more than 800 died.

Middle East Respiratory Syndrome (MERS) was identified in 2012 in Saudi Arabia, from where it spread to other countries in the Middle East.According to one of the versions of the WHO, camels were carriers of the virus. The manifestations of MERS are similar to the common flu: fever, cough, shortness of breath, general malaise, and diarrhea. The incubation period is 7-14 days. Rarely transmitted to children (according to statistics, children under 14 years old make up 3% of all cases). Mortality rate – 35% -40%. In 2012-2015, cases were reported in more than 20 countries, including the UK, Germany, China and the United States. In total, since September 2012, according to the WHO, more than 1.3 thousand people have been recorded in the world.laboratory confirmed cases of infection, including more than 460 fatal cases. Treatment using the blood plasma of patients who have successfully undergone coronavirus infection is used.

90,000 Four new dangerous sexually transmitted infections

  • Brune Nelson
  • Mosaic *

Photo author, iStock

Photo caption,

Scientists are concerned about the emergence of new dangerous sexually transmitted diseases

New diseases are emerging all the time, and sexually transmitted diseases are no exception.

We will tell you about four types of bacteria that cause dangerous new STDs and pose a serious threat to human health.

1. M Eningococcus

Neisseria meningitidis bacteria cause meningococcal infection, which can lead to fatal damage to the nasopharyngeal mucosa, as well as the membranes of the brain and spinal cord.

Previously, meningococcal infection was mainly associated with meningitis – inflammation of the lining of the brain, often with a fatal outcome.

However, now it is increasingly referred to as a urogenital type of infection.

In one of the studies of the 1970s. describes a case of autofellation in chimpanzees – the transfer of meningococcal bacteria from the oral cavity to the area of ​​the penis.

Carriers of the infection are 5-10% of adults. Typically, the bacteria Neisseria meningitidis live in the human nasopharynx. The bacteria, doctors say, are transmitted during oral sex.

Outbreaks of this disease have been reported in Europe, Canada and the United States.As a rule, gays and bisexuals are carriers of the infection.

A close relative of Neisseria meningitidis is the causative agent of gonorrhea, Neisseria gonorrhoeae. In 2015, the Neisseria strain was isolated in the United States, which is the result of genetic recombination of the DNA of both bacteria. This type of infection caused outbreaks of the disease in several cities in the United States in 2015.

One of the studies investigated cases of inflammation of the urethra caused by meningococcal bacteria.It was about a specific group of men. According to scientists, the infection was transmitted during oral sex.

Scientists have determined that the DNA of the strain that caused the outbreak of the disease in several US cities in 2015 was formed by genetic recombination with a similar infection – gonococcus, which causes gonorrhea.

This strain is highly contagious, that is, it spreads faster than others among people.

The five types of Neisseria meningitidis cause the majority of disease cases worldwide.Fortunately, there are two vaccines against them that work effectively against all five types of bacteria.

2. M Icoplasma genitalium

Mycoplasma genitalium (Mycoplasma genitalium) is one of the smallest bacteria, but the disease it causes is one of the most dangerous sexually transmitted infections.

This bacterium became known in the 1980s. At the moment, it is carried by 1-2% of the world’s inhabitants – mainly adolescents and young people.

Photo author, iStock

Photo caption,

Infection with mycoplasma genitalium can resemble chlamydia. This infection is especially dangerous for the health of women

Often, the infection is asymptomatic, or symptoms characteristic of gonorrhea or chlamydia may appear – inflammation of the cervix or urethra.

Since this infection can provoke pelvic inflammatory disease in women, the consequences of infection can be quite serious – including infertility, miscarriage, premature birth and missed pregnancies.

Although condoms protect against this infection, doctors are concerned that the bacteria mycoplasma genitalium is actively developing resistance to antibiotics such as azithromycin and doxycycline.

“I am concerned that this microorganism is developing more resistance [to antibiotics] and the infection is becoming more prevalent,” says Matthew Golden, director of the Seattle and King County HIV and STD Program.

Timely diagnosis and early treatment, scientists hope, will help prevent the bacteria Mycoplasma genitalium from turning into a superbug.

3. W Flexner’s needle

Shigellosis is a group of diseases caused by bacteria of the Shigella genus, with a fecal-oral transmission mechanism.

Infection with Shigella flexneri results in dysentery, which causes severe stomach cramps and bouts of diarrhea mixed with blood and mucus.

Photo author, iStock

Photo caption,

Infection with Shigella flexneri results in dysentery, which causes severe stomach cramps and bouts of diarrhea.

It used to be thought that children and travelers going to poor countries were more susceptible to the disease.

However, since the 1970s. cases of shigellosis are increasingly being reported among gays and bisexuals.

Scientists believe that in these cases the bacteria are transmitted during anal and oral sex. With the emergence of a new pathway for the spread of infection, outbreaks of the disease have been noted around the world.

Demeter Daskalakis, a spokesman for the New York City Department of Health, says the sexually transmitted disease is also becoming resistant to antibiotics – including azithromycin, which is also used to treat gonorrhea.

Experts are concerned that the use of this antibiotic to treat various types of shigellosis could potentially lead to the emergence of a superbug that causes gonorrhea. Doctors have developed more sophisticated treatments for this STD without the use of antibiotics.

4. B Generic Lymphogranuloma (VLH)

This disease is caused by a rare strain of Chlamydia trachomatis bacteria, says Christopher Schissl, physician at One Medical Clinic in San Francisco.

Photo author, Science Photo Library

Photo caption,

The danger is that the causative agents of new diseases quickly develop resistance to existing antibiotics

When infected, abscesses and ulcers first appear in the genital area, then the infection penetrates the human lymphatic system.

The disease can resemble inflammatory bowel disease and can lead to chronic and severe disruption of bowel function, such as fistula formation or narrowing of the bowel.

Over the past 10 years, lymphogranuloma venereum has become a fairly common disease in Europe and North America. As a rule, the disease is diagnosed in gay and bisexual men.

As with chlamydia, this disease increases the risk of contracting HIV.

According to doctors, the use of condoms reduces the risk of contracting this infection. Treatment for VLH involves taking antibiotics (such as doxycycline) for three weeks.

Intestinal infections: types and symptoms

At the end of a long hot summer, when the season is already over and the sea has been warm for a long time, the number of dangerous bacteria increases in the sea water.We all know that the water is not perfect, and at the end of August, you need to be especially careful.

Intestinal infections are parasitic, fungal, protozoal, viral and bacterial. The most common are bacterial, viral and parasitic, less often fungal and protozoal. They are mainly transmitted by fecal-oral, airborne droplets and contact. What does it mean? Through dirty hands, unwashed vegetables and fruits, stale food, contaminated water, and it is not necessary to swallow it, it is enough to just get it into your mouth (which is what happens when swimming in the sea).Water parks are even more dangerous. The household contact route is infection through household items, and the greatest danger is posed by coolers in public places, elevator buttons in apartment buildings, door handles of shops, pharmacies, canteens, public toilets, etc. If possible, do not let small children touch them! And of course, if you touched it, then don’t put your hands in your mouth, don’t touch your face. If you are outdoors, you can wipe your child’s hands with antibacterial wipes, and then, at home, wash them well.An older child who walks alone should be given such napkins with him.

Acute respiratory infection with abdominal syndrome is transmitted by airborne droplets, fecal-oral route, which means that you can get infected even just when you visit a store. Adults who smoke are also at risk of becoming infected more often than others: when they leave a crowded office, they touch the doorknob, they take a cigarette, and they put it in their mouths. The use of septic tanks in private houses also makes a significant contribution to the spread of intestinal infections, because after cleaning, industrial water is released onto the landscape.

The most common intestinal infections at the end of summer are viral, bacterial ones also occur. They usually have the following symptoms: weakness, lethargy, high fever, loss of appetite, refusal to eat, nausea, vomiting, loose stools, and sometimes a rash. In no case should you try to cope with an intestinal infection on your own, especially when it comes to a child. It is best to call a doctor at home or bring a patient to Teremok Zdorovya. Often people come to the pharmacy and ask the pharmacist to give them something “for diarrhea” and “for fever”.This is the wrong approach! The treatment of viral and bacterial intestinal infections is very different, so in no case can you treat yourself! Insufficiently effective treatment of intestinal infection can lead to serious complications (for example, to the kidneys), and then the child will have to stay in the hospital for a long time. In addition, only a doctor can correctly assess the severity of the intoxication syndrome, correctly and timely stop it immediately upon treatment, without delay. For this in the price list of the clinic “Teremok zdorovya” there is such a service: relief of an emergency of moderate severity.This service includes examination by a therapist and pediatrician, as well as all necessary urgent measures (intravenous and intramuscular injections, thermometry, etc.) and the appointment of further treatment at home. In addition, only a doctor can prescribe the necessary tests to make sure that the treatment went well, the patient does not have any dangerous intestinal infections, and there will be no complications. You can make an appointment with a pediatrician, a therapist by clicking on the link.

My personal experience: When I went home, the largest number of calls for intestinal infection came from Adler, Kurortny Gorodok.And when asked why they got sick, I received standard answers: yesterday we went to the water park, drank lemonade, which is sold from barrels on the street, and swam. The fewest such calls were from the Olympic Park. As my patient engineers, involved in the Olympic construction, explained to me later, the treatment facilities there are new and built according to European standards.

The team of doctors “Teremok Health” wishes you a pleasant and safe way to spend the last days of August and stay healthy!

Children’s infectious diseases, symptoms and treatment

Description of the problem

The infectious process in a child has its own characteristics.The response of organisms of children of different ages to the effect of an infectious agent varies greatly. In babies, the immune system remains immature for a certain time and cannot function normally, therefore, many diseases in childhood are more severe than in adults.

Why are children more susceptible to infections than adults?

  1. Children are more susceptible to infectious diseases, not only because of the weak functioning of the immune system, but also because of the thinness, dryness and looseness of the surface layer of the skin, which must act as a protective barrier.
  2. The next obstacle to infection is the lymph nodes, which are rather poorly developed in babies, have a loose capsule, but many vessels. In this regard, the lymph nodes do not retain pathogens properly, and the infection spreads much more easily throughout the body.
  3. Another feature is that the child’s immune system weakly produces interferons – proteins with antiviral properties. Therefore, acute respiratory viral and rotavirus infections are among the most common childhood diseases.They are especially often observed in children aged 6 months to 2 years, because the child loses the passive immunity received from the mother, and his body cannot yet produce its own antibodies.

Due to the immaturity of the immune, nervous, circulatory and other systems of the body, infectious diseases in babies are often atypical, so the parents themselves cannot recognize them without the help of doctors.

What is the best way to get sick in childhood?

Some infections, on the other hand, are easier in children than in adults, such as chickenpox or rubella.Therefore, babies who have been in contact with a sick child are not initially isolated in such cases. They simply require close monitoring, and isolation becomes necessary when symptoms of illness appear. After recovery, children develop stable lifelong immunity.

Complications of these diseases are rare, but they are very serious, therefore, it is necessary to periodically consult a doctor until your child is fully recovered in order to exclude the possibility of complications.

How can you protect your child from infections?

Pregnant women and those who are just planning motherhood should be extremely careful, because some infectious agents can penetrate the fetus through the placenta, cause it to have congenital diseases and various malformations.

It should be borne in mind that infectious diseases in children’s groups are transmitted very quickly, because children are constantly in contact with each other, sometimes they neglect the rules of hygiene.Therefore, if you find signs of an infectious disease in your child, he must be isolated, that is, temporarily stop attending kindergarten or school. This is necessary, firstly, to comply with bed rest, because high physical activity during an illness can lead to the spread of infection throughout the body. Secondly, this way you protect other children from infection.

Do not forget that some infectious diseases are transmitted to children and from parents. For example, gastritis and gastric ulcer can also result from infection – the presence of Helicobacter pylori in the digestive system (do a test for Helicobacter), which can be transmitted with saliva.Therefore, it is highly undesirable to use one spoon or fork with a child.

In order to prevent the appearance of intestinal infections, you should sterilize children’s dishes, subject food to heat treatment, and in the future teach your baby to wash his hands after using the toilet, before eating.

Vaccinations and strengthening of children’s immunity

Vaccination, which is carried out in our clinic by experienced staff, plays a huge role in the prevention of infectious diseases.Weakened infectious agents or their components are introduced into the child’s body. In response, the child’s immune system begins to produce antibodies, and your child will already be fully protected against a real infectious disease.

Undesirable consequences from the introduction of vaccines are still observed, so our doctor must definitely examine the baby before being vaccinated. Some vaccines are not administered to weakened and sick children – they need to wait for recovery. Most doctors believe that a slight increase in body temperature and mild malaise is a normal body response to the vaccine.By vaccinating your child in our clinic, you protect him from many serious infectious diseases.

For the purpose of emergency prevention, ready-made protective antibodies are used. However, after a while they die, and the child loses passive immunity.

If your baby suffers infectious diseases more often than 8 – 10 times a year, there is a reason to also consult an immunologist to assess the functioning of the immune system.

Diagnostics and treatment by our pediatricians

To diagnose a disease, our doctors sometimes resort to additional research methods:

  • general blood test
  • taking biological fluids for culture on culture media
  • polymerase chain reaction (PCR), reaction complement binding (CSC), enzyme-linked immunosorbent assay (ELISA)
  • X-ray
  • Ultrasound for children.

Many (but not all) infectious diseases in children are treated with antibiotic therapy. Today, many parents already know that antibiotics are useless for viral infections, but doctors still sometimes prescribe them, for example, for acute respiratory infections. The thing is that with a very severe course of a viral infection, it is much easier for bacteria to penetrate into a weakened child’s body. In order to prevent the addition of secondary microflora, the doctor prescribes a course of antibiotic therapy, but parents should not make such decisions on their own.Even if you are sure that the disease in your child is caused by bacteria, do not rush to the pharmacy for antibiotics. Often, the causative agents of bacterial infection are sensitive only to some of them, but they are completely immune to the drugs of another group, and only an experienced doctor can tell you about this.

Due to the fact that the child’s body often reacts very violently to the penetration of an infectious agent, babies need non-specific symptomatic therapy. So, with intestinal infections, children lose a lot of fluid and electrolytes, and sometimes only infusion therapy can make up for these losses.This once again proves the need to seek medical help in the presence of an infectious disease in a child.

The pediatrician of our clinic will not only help to accurately identify and completely remove the infection from the body of your child, but also do it in the most gentle and painless ways that will not cause your baby to have any allergic reactions or fear.

90,000 Future epidemics: what other threats can we face

When and how the COVID-19 pandemic will end remains to be seen.What is the likelihood that a major new epidemic could occur in the near future? Where does the threat come from? And can this be prevented?

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Already, many experts are confident that the virus that caused the outbreak of a new disease will forever go down in the history of mankind. SARS-Cov-2 has done what no other virus or bacteria has been able to do over the past 100 years: it locked most of the world’s population at home, paralyzed not only the social, but also the economic life of many countries. It has become a scientific enigma for the world academic community.The pathogenesis of the deadly disease COVID-19, which it causes, has not yet been solved. But it is no less significant that SARS-Cov-2 helped everyone to realize that the threat of a new infection is now as relevant to humanity as it was 100, 200 or 300 years ago.

About the expert: Sergey Alkhovsky – Doctor of Biological Sciences, Head of the Biotechnology Laboratory of the National Research Center for Epidemiology and Microbiology named after Honorary Academician NF Gamaleya of the Ministry of Health of Russia.

A new epidemic – is it possible?

Such an event can happen quite suddenly, and in different parts of the world. Right now we are all concerned about COVID-19, but before that there was an outbreak, for example, of the Ebola virus in Africa. Also, by the way, a virus associated with bats. And before that, there was Zika fever, and everyone was very worried about it. Moreover, it was completely incomprehensible why suddenly this virus, in general, known for a long time, began to spread at such a speed into new areas and cause such consequences.And before that, in 2009, there was a new pandemic swine flu virus h2N1. Even earlier, new variants of avian influenza constantly appeared in Asia, which became pathogenic for humans. By the way, the modern strain of bird flu cannot yet be transmitted from person to person. But it is likely that such a strain will appear and will spread in the human population. Therefore, new outbreaks are possible. And in order to understand where and with what probability new infections can come, modern virology must solve a very serious problem – it is necessary to describe completely all zoonoses in natural reservoirs that have such a dangerous potential.

Zoonoses (zoonotic infections) – a group of infectious and parasitic diseases, the causative agents of which parasitize in the body of certain species of animals, and for which animals are a natural reservoir.

This is a very ambitious task. But this must be done, since all known human viruses are derived from animal viruses. And most importantly, this process continues at the present time.

Viruses from animals continue to be transmitted to humans – for example, new coronaviruses or new variants of the influenza virus appear.All these events are of the same order.

And in order to have at least some ability to predict future threats of infection, it is necessary to fully study these natural foci. Of course, this has been done before. But, unfortunately, it used to be very difficult to isolate a virus from a natural focus and identify it – even at least see it through a microscope.

Let me give you a simple example: here you take, for example, some kind of sample from a patient. How do you know if there is a virus there or not? Plus, you don’t know what the virus is.For a very long time, virologists were engaged in collecting various materials, including from real patients, and trying to find a certain model system that could be infected and see whether the virus went from there or not. In the simplest case, laboratory animals became such a model system. For example, mice. If you successfully infected a mouse, and it really got sick, then you can say that you have isolated a strain of the virus. What if she didn’t get sick? Does this mean that there is no virus there? Or does it mean that a virus simply cannot grow on this model?

This situation continued until 2010, when genomic sequencing technologies appeared.Only then did we get the opportunity, using genomic analysis, to study a particular sample and see in it the genomes of all viruses that, roughly speaking, “float” in it. And this revolutionary shift, this new era in virology – it has just begun.

Only now we got the opportunity to discover viruses at a really high speed – tens and hundreds of new viruses a year. With the advent of new technologies and opportunities in the field of bioinformatics, in the field of big data processing, the task of describing all zoonotic viruses seems to be quite solvable.This, of course, is very expensive, but such work is already underway.

Modern working methods have allowed scientists to set themselves even more fundamental problems than describing all zoonoses. For example, there is such a program, it is called the “Global Virome Project”. The goal of the project is to describe in general all viruses that exist on Earth. Including those that live in the oceans, seas, soil, animals, insects, plants – everywhere else. This is really difficult.

What natural foci of viruses are of concern to scientists?

The situation here is a little simpler than it seems.The fact is that we are not talking about all natural foci that are on the planet, but about those natural reservoirs with which a person is constantly in contact. These include, for example, rodents. In particular, in Russia, vole mice are very widespread, carrying viruses of hemorrhagic fever with renal syndrome.

Hemorrhagic fever with renal syndrome (HFRS) is an acute viral natural focal disease characterized by systemic lesions of small vessels, hemorrhagic diathesis, hemodynamic disorders.And also a kind of kidney damage of the type of acute interstitial nephritis with the development of acute renal failure. The causative agent of HFRS belongs to the Bunyaviridae family and belongs to an independent genus – Hantavirus. It replicates in the cytoplasm of infected cells. Hantaviruses are polytropic, they are capable of infecting monocytes, cells of the lungs, kidneys, liver, salivary glands. Today, more than 30 serologically and genetically different hantaviruses are known.

Every year in Russia more than ten thousand cases of this disease are recorded. And the viruses that cause such a dangerous disease are carried by the vole mice. They come to our homes from the fields for the winter, quietly coexist with us until spring , and all this time the virus is excreted in their feces. So he gets to the person. That is, we are constantly in contact with this natural reservoir of a very dangerous infection.

Bats are also very interesting. These are generally very unusual animals in terms of their ecology, immunology – they have many interesting features.They are mammals that behave like birds. They live in large colonies and can fly long distances. These colonies can, in turn, be very crowded. Moreover, within one such colony there can be many different species of bats. This means that they constantly exchange their viruses with each other. Plus, they have their own characteristics of immunity: the pro-inflammatory reaction to various kinds of viruses, apparently, is much less pronounced in them than in humans. This topic is not well understood yet, by the way.And, nevertheless, 90,416 bats are another large and potentially dangerous natural reservoir with unknown infectious agents. With whom, by the way, the person also often contacts. In warm regions, bats live in attics in residential buildings or on the roofs of various residential buildings. And their viruses are also spread in feces.

Another reservoir is mosquitoes with ticks. When you go into the forest and a mosquito or a tick bites you, then, accordingly, all the viruses that are in them are transferred to you.

Of course, we cannot capture all such animals and insects and study them. But we already know certain natural reservoirs of infections with which we are constantly in contact. You can start the study with the same bats. Considering that we already know that this is one of the main sources from where we expect new threats in the near future.

But it is important to understand that there are a number of known infections that are also of concern to scientists. For example, there are many different smallpox viruses: mice, cows, other animals.Human infections with monkeypox virus are constantly being reported in Africa. Serious attention should also be riveted to this today.

There is a list of known infections that already cause very serious damage to humans and put them in constant danger. There is a group of so-called arboviruses. These are viruses that are transmitted by mosquitoes. They also have the potential to acquire new pathogenic properties. We have all heard about Dengue fever, yellow fever. Not long ago, there was an outbreak of Zika fever in the human population. But these insects are constantly expanding their habitat, which is facilitated by climate change. In the south of Russia, on the northern coast of the Krasnodar Territory, as well as in Italy, France, in a number of Eastern European countries, invasive species of tropical mosquitoes, carriers of infections, appear.In the case of arboviruses, it is extremely important to take into account the climate, because in order for them to accumulate in sufficient quantities, for successful infection, a certain number of warm days are needed. Accordingly, if there is a heat, all the prerequisites arise for the virus to accumulate in quantities sufficient to infect a person.

Why is the virus changing its host?

The virus, like any other living creature, is constantly trying to expand its habitat.Of course, it is a mistake to think that a virus decides or does not solve something, it does not possess thinking. Viruses are autonomous genomes that can pack into a capsid. This definition immediately emphasizes their difference from cellular organisms, whose genome is located inside the cell. Viruses are a separate branch of life on Earth, their genome is packed not into a cell, but into a capsid.

Capsid is the outer shell of the virus, consisting of proteins. The capsid performs several functions: protecting the genetic material (DNA or RNA) of the virus from mechanical, physical and chemical damage.

Viruses are also called obligate cellular parasites, since their genome, packed in a capsid, can reproduce only when it gets into some foreign cell. Therefore, the transfer of a virus from one host to another is not some meaningful mission. It’s just an evolutionary process. Viruses do this in order to expand their living space, increase their population and survive.

It is very difficult for a virus to master a new host. The severe course of the disease that they cause always affects its spread. That is, if an infected person dies in three days, he does not have time to transmit the virus to anyone. Accordingly, it is absolutely not “in the interests” of the virus. To survive in the population, he is forced to adapt, to evolve so as to successfully continue to reproduce.

If we talk about seasonal coronaviruses, which have long been in our population and do not cause serious diseases, then we do not know exactly from which specific animal viruses they originated. Once they were passed on to us from their predecessor host and through a long evolution became a completely different species.But phylogenetically, we understand that they come from the same common ancestor. This is the result of evolution. And this is the situation with all human viruses, all of them are former zoonoses, there is no doubt about it.

We carried some part of the viruses in the process of evolution from primates, and they stayed with us in this way. And all the other disease-causing viruses that we know today were acquired from an evolutionary point of view not so long ago.

In the case of some viruses, we already more or less know exactly who the original host was. For example, it is believed that the smallpox virus came to us from camels. When humans domesticated these animals and began to closely contact them, this virus passed on to humans and, again, began its own evolution as a new species – the human smallpox virus.

Or, for example, measles – presumably got to us from dogs. When we began to domesticate wolves, the virus passed from them to humans and began its own evolution. This has been the case at all times and will continue to do so.But I think that humanity can handle it. This can be seen in the current COVID-19 epidemic. Judge for yourself: registration of patients began around the beginning of December 2019. And a month later, the full genome of SARS-Cov-2 was available, which made it possible to immediately start developing tests, studying its biology, genetics, and starting the production of a vaccine. It turned out that within two to four months we are able to establish the production of millions of tests. Moreover, for the genome, and for antibodies, and for the antigen. But in the entire history of the confrontation between humans and viruses, this has never happened before.Looking at all this, I would generally say that humanity may no longer be threatened with such destructive and devastating virus epidemics.

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