How long does the flu typically last. What are the common symptoms and their progression. When should you seek medical attention for flu symptoms. How can you speed up recovery from the flu.

The Typical Duration of Flu: What to Expect

Understanding the timeline of flu symptoms is crucial for managing expectations and seeking appropriate care. The flu, unlike the common cold, tends to have a rapid onset and can leave individuals feeling incapacitated for several days.

Generally, flu symptoms appear within a few days of infection and peak between days 2 and 4. Most people start feeling better after 5-7 days, but it’s important to note that recovery times can vary.

• Typical flu duration: 3-7 days for most people
• Peak symptom period: Days 2-4
• Low energy may persist: Up to 2 weeks
• Lingering cough: Possible for up to 8 weeks

Is it possible for flu symptoms to fluctuate? Indeed, some individuals may experience symptoms that improve and then worsen again, or they might find their symptoms are more severe at certain times of the day, such as in the morning.

Flu Symptom Timeline: From Onset to Recovery

The progression of flu symptoms follows a relatively predictable pattern, though individual experiences may vary. Understanding this timeline can help you gauge your recovery and determine when to seek medical attention.

Day 1-2: Sudden Onset

Unlike colds, which develop gradually, flu symptoms often appear suddenly. Within hours, you may transition from feeling fine to experiencing:

• High fever (often the first symptom)
• Chills
• Muscle aches
• Headache
• Extreme fatigue

Days 2-4: Peak Symptoms

During this period, symptoms typically intensify. You may experience:

• Persistent high fever
• Dry cough
• Sore throat
• Vomiting (in some cases)
• Congestion

Days 5-7: Gradual Improvement

For many, this marks the beginning of recovery. Some may feel well enough to return to work or school, but it’s crucial to stay home for 24 hours after your fever breaks without the use of fever-reducing medication.

Beyond Day 7

While most people feel significantly better by this point, it’s not uncommon for some symptoms, particularly fatigue and cough, to persist for several more days or even weeks.

Factors Affecting Flu Duration and Severity

The duration and severity of flu symptoms can vary based on several factors. Understanding these can help you better manage your expectations and take appropriate precautions.

Age and Health Status

Certain groups may experience longer-lasting or more severe symptoms:

• Infants and young children
• Older adults (65 years and older)
• People with chronic respiratory diseases
• Individuals with weakened immune systems

These groups are also at higher risk for serious flu complications, such as pneumonia and breathing difficulties.

Flu Vaccination Status

Does getting a flu shot affect symptom duration? While the flu vaccine doesn’t guarantee immunity, it can influence the course of the illness if you do get infected. People who receive the flu shot and still contract the virus often experience:

• Less severe symptoms
• Shorter duration of illness
• Reduced risk of serious complications

Antiviral Treatment

Antiviral drugs, such as oseltamivir (Tamiflu), can significantly impact the course of the flu when taken early. These medications can:

• Shorten the duration of symptoms
• Reduce the severity of symptoms
• Lower the risk of serious complications

For maximum effectiveness, antiviral treatment should be started within 48 hours of symptom onset.

Recognizing and Managing Flu Complications

While most people recover from the flu without incident, complications can occur and may require medical attention. Recognizing the signs of complications is crucial for timely intervention.

Common Flu Complications

• Pneumonia
• Bronchitis
• Sinus infections
• Ear infections (especially in children)
• Worsening of chronic health conditions

Can flu complications resolve on their own? Unlike typical flu symptoms, complications are unlikely to improve without medical intervention and can sometimes be life-threatening.

When to Seek Medical Attention

Consult a healthcare provider if you experience:

• Difficulty breathing or shortness of breath
• Persistent pain or pressure in the chest or abdomen
• Persistent dizziness, confusion, or inability to arouse
• Seizures
• Severe muscle pain
• Symptoms that improve but then return with fever and worse cough

For children, additional warning signs include:

• Rapid breathing or trouble breathing
• Bluish skin color
• Not drinking enough fluids
• Not waking up or not interacting
• Being so irritable that the child does not want to be held
• Flu-like symptoms that improve but then return with fever and worse cough

Effective Strategies for Flu Recovery

While there’s no cure for the flu, several strategies can help alleviate symptoms and promote faster recovery. Implementing these measures can make a significant difference in your comfort and healing process.

Rest and Hydration

Two of the most crucial elements for flu recovery are:

• Getting plenty of rest to allow your body to fight the infection
• Staying well-hydrated to replace fluids lost through fever and sweating

Why is hydration so important during flu recovery? Proper hydration helps thin mucus secretions, making them easier to expel, and supports your immune system’s function. If you’re experiencing fever or vomiting, consider drinking electrolyte-rich fluids to prevent dehydration.

Over-the-Counter Medications

Certain medications can help manage flu symptoms:

• Acetaminophen or ibuprofen for fever and pain relief
• Decongestants to relieve nasal congestion
• Cough suppressants for persistent coughs

Always follow dosage instructions and consult with a healthcare provider if you have any underlying health conditions or are taking other medications.

Antiviral Medications

For optimal effectiveness, antiviral drugs should be started within 48 hours of symptom onset. These prescription medications can:

• Shorten the duration of the flu
• Reduce the severity of symptoms
• Prevent serious complications

Consult your healthcare provider to determine if antiviral treatment is appropriate for you.

Home Remedies

Several home remedies may provide symptom relief:

• Gargling with salt water for sore throat
• Using a humidifier to ease congestion and coughing
• Consuming warm liquids like herbal tea or broth
• Applying a warm compress to relieve sinus pressure

Preventing Flu Spread: Essential Practices

Preventing the spread of flu is crucial not only for your recovery but also for protecting those around you. Implementing these practices can significantly reduce the risk of transmission.

Self-Isolation

One of the most effective ways to prevent flu spread is to stay home when you’re sick. How long should you isolate yourself? Experts recommend staying home for at least 24 hours after your fever subsides without the use of fever-reducing medications.

Hand Hygiene

Proper hand hygiene is crucial in preventing the spread of flu viruses:

• Wash your hands frequently with soap and water for at least 20 seconds
• Use alcohol-based hand sanitizers when soap and water aren’t available
• Avoid touching your face, especially your mouth, nose, and eyes

Respiratory Etiquette

Protect others from your respiratory secretions:

• Cover your mouth and nose with a tissue when coughing or sneezing
• Dispose of used tissues immediately
• If you don’t have a tissue, cough or sneeze into your elbow, not your hands

Environmental Cleaning

Flu viruses can survive on surfaces for several hours. Regular cleaning and disinfection of frequently touched surfaces can help reduce transmission:

• Doorknobs and handles
• Light switches
• Keyboards and phones
• Bathroom fixtures
• Kitchen surfaces

Long-Term Impact of Flu: What to Expect After Recovery

While most people recover fully from the flu within a week or two, some individuals may experience lingering effects. Understanding these potential long-term impacts can help you manage your expectations and seek appropriate care if needed.

Post-Flu Fatigue

It’s not uncommon to feel tired and weak for several weeks after the acute phase of the flu has passed. This post-viral fatigue can persist for up to a month in some cases.

How can you manage post-flu fatigue? Gradual return to normal activities, maintaining good sleep hygiene, and proper nutrition can help speed up your recovery.

Persistent Cough

A dry, hacking cough can linger for up to 8 weeks after the flu. This is often due to inflammation in the airways and doesn’t necessarily indicate a continuing infection.

Increased Susceptibility to Other Infections

In the weeks following a bout of flu, your immune system may be weakened, potentially increasing your susceptibility to other infections. Taking care to maintain good health practices during this time is crucial.

Impact on Chronic Conditions

For individuals with pre-existing health conditions, the flu can lead to worsening of their chronic illness. This may require ongoing management and potentially adjusted treatment plans.

Who is most at risk for long-term flu impacts? Older adults, people with chronic health conditions, and those with weakened immune systems are more likely to experience prolonged effects from the flu.

Psychological Effects

The experience of being seriously ill with the flu can have psychological impacts for some individuals, including:

• Increased anxiety about health
• Depression related to prolonged illness and isolation
• Post-traumatic stress in cases of severe illness or hospitalization

If you’re experiencing persistent psychological effects after recovering from the flu, don’t hesitate to seek support from a mental health professional.

How long does the flu last? Timeline and recovery

Symptoms of the flu generally appear within a few days of infection. They usually peak between days 2 and 4, and most people feel better after 5–7 days. However, symptoms can last longer in some cases, and a cough may persist for several weeks.

The flu can leave a person unable to work, perform household duties, or tend to children for several days. Some people develop severe symptoms and may need hospital care.

In this article, we discuss how long the flu usually lasts, a timeline of the common symptoms, and when to see a doctor for treatment.

For people who do not develop serious flu complications, symptoms usually last 3–7 days. Some people find that their symptoms get better and then worse again or that they are worse at certain times of the day, such as in the morning.

Although fever and the most severe symptoms typically resolve within a week, some people have low energy for up to 2 weeks, and it is possible to experience a cough for up to 8 weeks.

The flu shot reduces the risk of getting the flu but does not eliminate it. However, people who still get the flu after receiving a shot tend to have less severe symptoms that last for a shorter period.

Antiviral drugs, such as oseltamivir (Tamiflu), can also shorten the length of the flu and lower the risk of serious complications.

Infants and very young children, older adults, and people with respiratory diseases may have symptoms that last longer. These individuals are also more vulnerable to serious flu complications, such as pneumonia and breathing difficulties.

According to the Centers for Disease Control and Prevention (CDC), about 200,000 people in the United States need to go to the hospital each year as a result of the flu.

Flu complications are unlikely to resolve on their own, and they can be a medical emergency. They may require a person to stay in the hospital. It can be weeks or even months before a person recovers from serious flu complications.

For more information and resources to help keep you and your loved ones healthy this flu season, visit our dedicated hub.

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Unlike the cold and other viruses, which present gradually, flu symptoms tend to appear suddenly. Within a few hours, a person may transition from feeling fine to having a fever and other symptoms.

A high fever occurs more commonly with the flu than with a cold, and it often appears before other symptoms.

The most common symptoms of the flu include:

• high fever
• chills
• muscle aches
• a headache
• weakness and extreme exhaustion
• a dry cough
• a sore throat
• vomiting
• congestion

The symptoms tend to peak between days 2 and 4. By day 5, some people begin to feel better. A few feel well enough to return to work or school.

However, it is important to stay at home for 24 hours after a fever breaks. If the fever only goes away with anti-fever medication, remain at home.

By day 7, most people feel significantly better, although some are still sick. It is not unusual for the flu to last longer than a week, so slow healing is not necessarily a bad sign. However, if the symptoms continue to get worse after a week, it may be best to see a doctor.

The best and most effective treatment for the flu is an antiviral flu drug. Taking this drug within 2 days of getting sick may shorten the duration of the flu and help a person avoid complications.

Before taking any anti-flu medication, a person can weigh up the risks and benefits with a doctor. It is important to tell the doctor about any previous health problems or drug reactions because some people experience side effects when they take anti-flu drugs.

Antibiotics cannot treat the flu. The flu is a virus, and antibiotics only treat bacterial infections.

However, some people develop secondary infections because of the flu. Children are especially vulnerable to ear infections, but adults can get them too. If symptoms suddenly change or get worse, this could mean that there is a new infection, which could be viral or bacterial.

The following strategies can help speed up the healing process:

• Resting and staying in bed.
• Avoiding going to work, school, or anywhere else, as this can spread the flu.
• Drinking plenty of fluids. If fever or vomiting occurs, try drinking an electrolyte drink to prevent dehydration.
• Using over-the-counter medications, such as ibuprofen or acetaminophen.
• Washing the hands frequently to avoid spreading the infection to other members of the household.

People should try to see a doctor within 24 to 48 hours after flu symptoms appear, as this is when antiviral treatments are most effective.

It is also important to see a doctor if symptoms do not improve after 7 days or new symptoms, such as ear pain, appear.

People should seek emergency medical treatment if:

• breathing becomes difficult or labored
• muscle pain is unbearable or severe enough to prevent walking
• a child develops a fever above 104°F
• when breathing, a child or infant makes loud sounds or pulls in the muscles around their ribs
• a person has seizures, loses consciousness, seems confused, or is unable to communicate effectively
• a baby under the age of 12 weeks develops a fever
• symptoms of chronic medical conditions get worse
• there is intense dizziness that does not go away after a few hours
• a person stops urinating or urinates very rarely
• symptoms get better but then return later and are worse

Most people who get the flu will have symptoms that last between 3 and 7 days. If they develop complications, they may be ill for longer.

Thousands of people die from the flu every year. Children, older adults, or people with compromised immune systems are much more vulnerable to flu complications. People should take the flu seriously by resting and avoiding public places until their symptoms disappear.

With rest and medical care, it is possible to recover even from serious complications. Anyone with severe flu symptoms should see a doctor. To reduce the risk of getting the flu again, a person can get the flu shot every year.

How long does the flu last?

Few common illnesses are more unpleasant than the flu. The aches and pains, chills, fever, and cough are bad enough; add in the other potential symptoms of flu, including runny nose, vomiting, diarrhea, fatigue, or sore throat, and you’ll want the illness to be over as soon as possible. How long does the flu last? And does treating flu help make it go away faster? The answers depend on your particular health.

Understanding flu

The flu—or influenza—is a highly contagious respiratory virus caused by one of three different virus types: influenza A, B, or C. The main way that illnesses like colds and the flu spread from person to person is through the droplets that sick people propel when they cough and sneeze. You can also get the flu by exposure to saliva passed by routine contact, such as kissing or sharing eating utensils.

How long does the flu last?

For most healthy people, the flu is an uncomfortable but short-term illness that resolves itself as the immune system fights it off. Symptoms usually appear from one to four days after exposure to the virus, and they last five to seven days. For people who’ve had a flu shot, the symptoms may last a shorter amount of time, or be less severe. For other people, the symptoms may last longer. Even when symptoms resolve, you may continue to feel fatigued.

Some people are at increased risk for complications from influenza. These people include:

• the very young
• people 65 or older
• people with chronic illnesses, such as asthma, heart disease, HIV, or diabetes
• pregnant women
• people with a body mass index (BMI) of 40 or higher

People in those groups may have weakened immune systems, and are at increased risk for the complication of pneumonia, which can be deadly.

Treating flu

If you get the flu, you should get rest and drink plenty of fluids. Take pain relievers to lower your fever and relieve the aches, such as:

• acetaminophen (Tylenol)
• ibuprofen (Advil, Motrin)
• naproxen (Aleve)

If you are at high risk of complications, and if it is early in the infection, your doctor may prescribe an antiviral drug for treating flu, such as oseltamivir (Tamiflu, generic versions).

Prevention

To better predict how long the flu will last, take steps to reduce your risk of contracting the virus and experiencing severe symptoms. Consider the following steps, as suggested in the Harvard Special Report A Guide to Women’s Health: Fifty and Forward.

• Get an annual flu vaccine.
• Wash your hands with soap and water before eating or touching your face.
• Contact your doctor for promptly if you get flu symptoms.
• Quit smoking. Smokers are more likely to get the flu than nonsmokers.

These steps won’t guarantee that you’ll escape the flu this year, but they may help prevent it. And they may help reduce the amount of time the flu lasts if you do become infected with the virus.

– By Heidi Godman

Executive Editor, Harvard Health Letter

Dispel misinformation about the flu vaccine, sickness, treatment, and recovery by finding out these 10 Flu Myths.

Hepatitis

Regarding the diagnosis and treatment of this type of disease

in children , you can contact by phone (8652) 24-13-61 (children’s department, head) – children’s hepatological center.

in adults – by phone (8652) 24-44-75 (adult department, head Olga Anatolyevna Kostenko) – adult hepatology center with outpatient reception.

What is hepatitis?

Viral hepatitis is a common and dangerous infectious disease. They can manifest themselves in different ways, but among the main symptoms are jaundice and pain in the right hypochondrium. To diagnose hepatitis, you need to do a blood test, urine test, and in difficult cases, a liver biopsy.

Of all forms of viral hepatitis, hepatitis A is the most common. From the moment of infection to the appearance of the first signs of the disease, it takes from 7 to 50 days. Most often, the onset of the disease is accompanied by a rise in temperature and may resemble the flu. Most cases end spontaneously and do not require active treatment. In severe cases, droppers are prescribed to eliminate the toxic effect of the virus on the liver.

The hepatitis B virus is transmitted sexually, by injection with non-sterile syringes in drug addicts, from mother to fetus. In typical cases, the disease begins with fever, weakness, joint pain, nausea and vomiting. Sometimes there are rashes. There is an increase in the liver and spleen. There may also be darkening of the urine and discoloration of the stool.

Hepatitis C is the most severe form of viral hepatitis, also called post-transfusion hepatitis. This means that they fell ill after a blood transfusion. This is due to the fact that testing of donated blood for the hepatitis C virus began only a few years ago. Quite often, infection occurs through syringes in drug addicts. Sexual transmission is also possible from mother to fetus. The greatest danger is the chronic form of this disease, which often turns into cirrhosis and liver cancer. Chronic course develops in approximately 70-80% of patients. The combination of hepatitis C with other forms of viral hepatitis sharply aggravates the disease and threatens with a fatal outcome.

Prevention of hepatitis.

To protect yourself from infection with hepatitis, you must follow simple rules.

Do not drink unboiled water, always wash fruits and vegetables, do not neglect the heat treatment of food. In this way, you can prevent infection with hepatitis A, the transmission of which is associated with contamination of food with the faeces of a sick person. The great rule “Wash your hands before eating” is a guarantee of health in this case too.

In general, contact with other people’s body fluids should be avoided. For protection against hepatitis B and C – primarily with blood. In microscopic quantities, blood can remain on razors, toothbrushes, nail scissors. Do not share these items with other people.

Measures are being taken to prevent infection with hepatitis in medical institutions. However, if you had an endoscopy or dental treatment ten to fifteen years ago, when the fight against hepatitis was not yet carefully organized, you need to get checked. There is still a small risk of infection today.

Never share syringes and needles for taking drugs. Never use non-sterile piercings and tattoos. Remember – the hepatitis virus is very tenacious and, in contrast to the AIDS virus, it persists in the external environment for a long time (sometimes up to several weeks). Invisible traces of blood can remain even on the straws used in the use of cocaine, so in this case, too, one should be wary of infection.

Hepatitis B is most commonly transmitted sexually, but hepatitis C can also be transmitted. Particular care must be taken when having sex during menstruation and anal intercourse, but sometimes oral sex can also be dangerous.

Hepatitis is also transmitted by the so-called “vertical” way – from mother to child during pregnancy, childbirth, during breastfeeding. With proper medical support, you can try to avoid infection of the baby – this will require careful adherence to hygiene rules and medication.

However, the mode of transmission of hepatitis very often remains unknown. To be completely calm, it is necessary to vaccinate.

How to distinguish influenza from SARS

In this article you will learn what is the difference between influenza and SARS and why you need to distinguish between these diseases for proper treatment and prevention.

Many people are accustomed to calling any ailment a “cold” and do not consider this condition dangerous. Indeed, there are similarities between all acute respiratory diseases. But they can be caused by different viruses and bacteria, run differently, and lead to different health outcomes. Therefore, the diagnosis and control of the doctor is actually very important.

At the first symptoms of a respiratory viral infection, you can contact a MedEx clinic physician. We will help to accurately determine the nature of the disease and quickly cure it.

Miscellaneous pathogens

The main difference between influenza and SARS is the reason. The causative agent of SARS can be any of more than 200 viruses (adenoviruses, parainfluenza, rhinoviruses, coronaviruses and many others). All respiratory viruses cause similar symptoms and require the same treatment, but from a scientific point of view, SARS is not one disease, but a large group.

With the flu, the situation is different: it is caused by a very specific virus. Of course, the flu virus exists in three different types and constantly mutates, but scientists constantly monitor these changes and take them into account when preparing for each season of the epidemic.

Miscellaneous onset and course of disease

An experienced doctor can recognize the cause of the disease by the way it began and proceeds. Therefore, at the appointment with the therapist, tell in detail about your feelings from the first day when you felt that you were sick.

The main differences are:

• Influenza usually starts very abruptly. Literally within an hour or two, a high temperature rises and chills begin. The person feels unwell and tends to lie down, even if there are no respiratory signs of the disease yet. At the same time, ARVI can develop gradually and begin with slight weakness and sore throat.
• The general condition of a sick person with ARVI is usually easier – there is weakness due to fever and unpleasant symptoms like a runny nose. During the flu, the patient often feels severe body aches, appetite disappears, sometimes weakness and dizziness literally do not allow to get out of bed. And most importantly, after the flu, weakness usually persists for another week or more.
• Complete recovery from SARS usually occurs within a week. Influenza usually lasts longer: up to 10 days the acute phase of the disease, 2-3 weeks – asthenic syndrome, that is, weakness and decreased performance due to intoxication of the body.

Slight differences in symptoms

In general, the picture for ARVI and influenza is similar: a person feels very cold, he is worried about respiratory manifestations of the disease and fever. But the difference still exists, and it is important to see it in order to consult a doctor in time at the slightest suspicion of the flu.

The most important differences between flu and SARS symptoms to be aware of:

• In ARVI, a runny nose and sneezing usually appear immediately, on the very first day of the disease. With influenza, these symptoms are initially absent, they can only join on the 2-3rd day of illness and are considered a complication.
• The body temperature during influenza is higher: it can rise to 38.5-40°C and stay for several days. If it’s the flu, it’s usually hard to bring down the fever. At the same time, ARVI rarely gives a temperature above 38 ° C, and after 2-3 days the fever subsides.
• Some symptoms are especially pronounced with influenza: chills, pain in the eyes and photophobia, increased sweating, intense headache, redness of the mucous membranes of the eyes. Dizziness may also appear. All this is a consequence of the fact that with influenza, intoxication of the body is stronger and develops faster.
• Influenza more often than SARS is accompanied by indigestion – especially in a child.
• Cough with ARVI usually appears immediately, and with influenza it may not occur at all or join on the 2-3rd day of illness. During the flu, the cough is dry, often accompanied by chest pain.

Flu vaccine available

Unlike SARS, influenza in adults and children can be prevented by vaccination. This is possible because although the flu virus is constantly evolving, it still comes in only 3 types: A, B and C. The number of strains is limited, and scientists constantly monitor their mutation, so they can prepare for each season of the epidemic.

What is important to know if you are planning to get a flu shot:

• It does not provide 100% protection. If a person has been vaccinated, this does not mean that he will definitely not get the flu this season and may not comply with preventive measures. But the risk is still reduced by 70-80%, and this is already a good indicator.
• Vaccination reduces the risk of complications from influenza and relieves symptoms of the disease. Even if a vaccinated person becomes infected, they are likely to recover from the flu more quickly and easily. Therefore, it makes sense to take root in any case.
• A vaccine is developed annually. Each season of the epidemic is dominated by different strains of the virus, so the vaccine formula is regularly adapted by scientists. The vaccine simultaneously provides protection against several of the most dangerous varieties of influenza that will be common this year.
• Vaccination should be done in advance, and not during the season of high incidence. The optimal margin of time to have time to form your own immunity is 3-4 weeks before the start of the season. In Russia, it usually begins in October-November, so the standard time for influenza vaccination is early autumn.

At the same time, it is impossible to vaccinate against SARS, because this is too large a group of viral diseases. To prepare for a seasonal outbreak of SARS, you should strengthen your immune system in advance with proper nutrition, hardening, healthy sleep patterns and other methods. And directly in the cold season, you need to take additional precautions: dress according to the weather, wash your hands more often and avoid crowded places unless absolutely necessary.

What do SARS and influenza have in common

Despite the differences in the symptoms of influenza and SARS in adults, there are some common points. Strictly speaking, the flu is also one of the varieties of SARS. But since it is more severe and more likely to lead to complications, it is important to diagnose it separately and distinguish it from all other respiratory infections.

What unites these two diagnoses:

• It is useless to treat both acute respiratory viral infections and influenza with antibiotics – these are diseases of a viral nature; drugs for their treatment are selected by a general practitioner after a personal consultation.
• The main thing for recovery is to keep the body calm, drink plenty of warm liquids and make sure that the body temperature does not rise excessively. These rules are relevant for any acute respiratory disease – an acute respiratory disease.
• Influenza and SARS are highly contagious and are transmitted in the same way: by airborne droplets, by physical contact with a sick person, or through surfaces that an infected person has touched.
• Epidemic nature: the incidence of SARS and influenza in Russia increases sharply every year in the autumn-winter period and in the spring. The peak incidence usually occurs in January-February. At this time, schools and kindergartens are closed for quarantine throughout the country, and polyclinics are overcrowded.
• At risk for SARS and influenza are children under 14 years of age, pensioners, pregnant women and adults with weakened immunity for various reasons. These groups of people are more likely to catch the virus and need to be monitored by a doctor during an illness.
• ARVI and influenza are fraught with similar complications: against their background, inflammatory processes can occur in the lungs and bronchi, middle ear, sinuses, and even in the heart or brain.