What are the common side effects of the yellow fever vaccine. How long do yellow fever vaccine side effects typically last. Who should exercise caution when considering the yellow fever vaccine. What are the rare but serious side effects associated with the yellow fever vaccine. How effective is the yellow fever vaccine in preventing infection.

What is Yellow Fever and How Does it Spread?

Yellow fever is a serious viral disease transmitted by infected mosquitoes. The virus is endemic to certain regions of Africa and South America, posing a risk to travelers visiting these areas. But what exactly causes yellow fever, and how does it affect the human body?

The yellow fever virus belongs to the Flaviviridae family and is primarily spread through the bite of infected Aedes or Haemagogus mosquitoes. When an infected mosquito bites a human, it introduces the virus into the bloodstream, where it begins to replicate.

Symptoms and Progression of Yellow Fever

The incubation period for yellow fever typically ranges from 3 to 6 days after infection. Many infected individuals may experience mild symptoms or none at all. However, for those who do develop symptoms, the disease can progress through several stages:

1. Initial stage: Characterized by fever, chills, headache, backache, and muscle aches
2. Remission stage: Some patients may see an improvement in symptoms
3. Toxic stage: Approximately 12% of symptomatic patients progress to this severe stage, which can include:
• Jaundice (yellowing of the skin and eyes)
• Bleeding tendencies
• Shock
• Organ failure
• Potential death

Is yellow fever always fatal? While the disease can be severe, not all cases lead to death. However, the toxic stage has a high mortality rate, underscoring the importance of prevention and vaccination for those at risk.

The Importance of Yellow Fever Vaccination for Travelers

For travelers venturing to regions where yellow fever is endemic, vaccination is crucial. The yellow fever vaccine is not only a protective measure but also a requirement for entry into certain countries. Why is this vaccine so important for international travel?

The yellow fever vaccine serves two primary purposes:

1. Individual protection: It helps prevent infection in travelers exposed to the virus
2. Public health measure: It prevents the importation and spread of the virus to non-endemic areas

Many countries require proof of yellow fever vaccination for entry, especially if travelers are arriving from or have passed through endemic areas. This requirement is enforced to protect both the individual traveler and the local population from potential outbreaks.

Yellow Fever Vaccine Recommendations

The Centers for Disease Control and Prevention (CDC) provides detailed recommendations for yellow fever vaccination based on travel destinations. These recommendations take into account the risk of virus exposure in different regions of Africa and South America.

Are all travelers to endemic regions required to get vaccinated? Not necessarily. While vaccination is generally recommended for travel to high-risk areas, there are some low-risk regions where vaccination might only be considered for certain travelers. Factors influencing this decision include:

• Duration of travel
• Season of travel (mosquito activity varies)
• Specific locations within a country
• Planned activities that may increase mosquito exposure
• Individual health factors

It’s essential for travelers to consult with a healthcare provider or visit a yellow fever vaccination clinic to discuss their specific travel plans and determine if vaccination is necessary or recommended.

Understanding Yellow Fever Vaccine Side Effects

While the yellow fever vaccine is generally safe and effective, like all medical interventions, it can cause side effects. Understanding these potential reactions is crucial for individuals considering vaccination. What are the most common side effects of the yellow fever vaccine?

Common Side Effects

Most people who receive the yellow fever vaccine experience mild side effects, if any. These typically include:

• Low-grade fever
• Mild headache
• Muscle aches
• Fatigue
• Soreness at the injection site

These mild side effects usually appear within days after vaccination and resolve on their own within a week. They are generally not cause for concern and indicate that the body is building immunity to the virus.

Rare but Serious Side Effects

While uncommon, more severe reactions to the yellow fever vaccine can occur. These rare side effects include:

1. Severe allergic reactions (anaphylaxis)
2. Yellow fever vaccine-associated neurologic disease (YEL-AND)
3. Yellow fever vaccine-associated viscerotropic disease (YEL-AVD)

YEL-AND can cause inflammation of the nervous system, leading to symptoms such as confusion, seizures, or Guillain-Barré syndrome. YEL-AVD is a severe reaction that can cause multi-organ failure, resembling actual yellow fever infection.

How often do these serious side effects occur? The risk of severe adverse events is estimated to be about 1 per 250,000 doses for YEL-AND and 1 per 500,000 doses for YEL-AVD. While these risks are low, they underscore the importance of careful consideration before vaccination, especially for certain high-risk groups.

Who Should Exercise Caution with Yellow Fever Vaccination?

While the yellow fever vaccine is safe for most people, certain individuals may be at higher risk for adverse reactions. Who should be particularly cautious about receiving this vaccine?

High-Risk Groups

The following groups should consult closely with a healthcare provider before receiving the yellow fever vaccine:

• Adults 60 years and older
• Infants younger than 9 months
• Pregnant women
• Breastfeeding mothers
• People with weakened immune systems (e.g., HIV/AIDS, cancer patients)
• Individuals with thymus disorders or who have had their thymus removed
• Those with egg allergies (as the vaccine contains egg proteins)

For these groups, the risks of vaccination may outweigh the benefits, especially if traveling to areas with low risk of yellow fever exposure. Healthcare providers can offer guidance on alternative protective measures or whether a waiver for vaccination requirements might be appropriate.

Considerations for Older Adults

Why are adults over 60 considered a high-risk group for yellow fever vaccination? Studies have shown that older adults, particularly those receiving their first yellow fever vaccine, have a higher risk of severe adverse events. This increased risk is thought to be related to age-related changes in immune function.

For travelers over 60, healthcare providers will carefully weigh the risks and benefits of vaccination, considering factors such as:

• Overall health status
• Specific travel plans and destinations
• Previous yellow fever vaccinations
• Potential for exposure to the virus

In some cases, a medical waiver may be provided if the risks of vaccination are deemed too high. However, this decision should be made on an individual basis in consultation with a travel medicine specialist.

Effectiveness and Duration of Yellow Fever Vaccine Protection

The yellow fever vaccine is highly effective in preventing infection. But how long does this protection last, and are booster doses necessary?

Initial Vaccine Effectiveness

The yellow fever vaccine is considered one of the most effective vaccines available. Within 10 days after vaccination, 80-100% of recipients develop protective antibodies against the virus. By 30 days post-vaccination, nearly 100% of individuals have developed immunity.

How long does it take for the yellow fever vaccine to become effective? While some protection begins to develop within days, full immunity is generally considered to be achieved 10 days after vaccination. This is why many countries require travelers to show proof of vaccination at least 10 days before entry.

Long-Term Protection and Booster Doses

For many years, it was standard practice to recommend booster doses of the yellow fever vaccine every 10 years. However, recent research has shown that a single dose of the vaccine provides long-lasting protection for most individuals.

In 2013, the World Health Organization (WHO) declared that a single dose of yellow fever vaccine provides lifelong protection for most people. This decision was based on a comprehensive review of vaccine studies and epidemiological data.

Are there any exceptions to this lifelong protection? While a single dose is sufficient for most, there are some situations where a booster dose might be recommended:

• Individuals with weakened immune systems
• Women who were pregnant when they received their first dose
• Those who received their first dose before an organ transplant
• Laboratory workers who routinely handle live yellow fever virus

Additionally, some countries may still require proof of vaccination within the last 10 years for entry, regardless of the WHO recommendation. Travelers should always check the specific requirements for their destinations.

Preventive Measures Beyond Vaccination

While vaccination is the most effective way to prevent yellow fever, it’s not the only measure travelers should take. What other steps can individuals take to protect themselves from yellow fever and other mosquito-borne diseases?

Mosquito Bite Prevention

Reducing exposure to mosquito bites is crucial, especially in endemic areas. Effective mosquito prevention strategies include:

• Using EPA-registered insect repellents containing DEET, picaridin, IR3535, oil of lemon eucalyptus, para-menthane-diol, or 2-undecanone
• Wearing long-sleeved shirts and long pants
• Treating clothing and gear with permethrin or purchasing pre-treated items
• Staying in accommodations with air conditioning or screened windows and doors
• Using bed nets when sleeping in open-air or non-screened areas

Is it necessary to take these precautions even if vaccinated? Yes, these measures are important not only for yellow fever prevention but also for protection against other mosquito-borne diseases such as malaria, dengue, and Zika virus.

Travel Planning and Health Precautions

Beyond mosquito bite prevention, travelers to yellow fever endemic areas should:

1. Consult a travel medicine specialist at least 4-6 weeks before departure
2. Research the specific health risks associated with their destinations
3. Ensure all routine vaccinations are up to date
4. Consider other travel-related health precautions, such as malaria prophylaxis if necessary
5. Purchase comprehensive travel health insurance
6. Carry a detailed list of medications and medical conditions

By combining vaccination, mosquito prevention, and thorough travel planning, individuals can significantly reduce their risk of yellow fever and other travel-related health issues.

Global Efforts in Yellow Fever Control and Eradication

Yellow fever remains a significant public health concern in many parts of the world. What efforts are being made on a global scale to control and potentially eradicate this disease?

Vaccination Campaigns

One of the primary strategies for yellow fever control is mass vaccination campaigns in endemic areas. These efforts aim to:

• Increase population immunity in high-risk areas
• Prevent outbreaks and reduce the risk of epidemics
• Protect vulnerable populations, including children and rural communities

The World Health Organization, in collaboration with national governments and other partners, has implemented the Eliminate Yellow Fever Epidemics (EYE) strategy. This initiative aims to protect at-risk populations, prevent international spread, and contain outbreaks rapidly.

Vector Control Measures

Controlling the mosquito populations that transmit yellow fever is another crucial aspect of disease prevention. Vector control efforts include:

• Environmental management to reduce mosquito breeding sites
• Use of insecticides and larvicides
• Implementation of biological control methods
• Community education on mosquito prevention

These measures not only help control yellow fever but also contribute to the prevention of other mosquito-borne diseases.

Surveillance and Early Warning Systems

Effective surveillance is critical for early detection and response to yellow fever outbreaks. Global efforts in this area include:

1. Strengthening laboratory capacity for rapid diagnosis
2. Improving disease reporting systems
3. Enhancing epidemiological surveillance in high-risk areas
4. Developing and implementing early warning systems for potential outbreaks

These surveillance efforts allow for quicker response times and more effective containment of outbreaks when they occur.

Research and Development

Ongoing research plays a crucial role in the fight against yellow fever. Current areas of focus include:

• Development of new and improved vaccines
• Studies on long-term vaccine efficacy and safety
• Research into the ecology and transmission dynamics of yellow fever virus
• Exploration of novel vector control methods

Are these global efforts making a difference? While yellow fever remains a threat in many areas, coordinated international efforts have significantly reduced the incidence of large-scale epidemics. However, continued vigilance and investment in prevention and control measures are necessary to maintain progress and work towards potential eradication.

Yellow Fever | Disease Directory | Travelers’ Health

What is yellow fever?

Yellow fever is a serious disease caused by the yellow fever virus.

Most people infected with yellow fever virus do not get sick or have only mild symptoms. People who do get sick will start having symptoms (e.g., fever, chills, headache, backache, and muscle aches) 3–6 days after they are infected. About 12% of people who have symptoms go on to develop serious illness: jaundice, bleeding, shock, organ failure, and sometimes death. 

How does yellow fever spread?

Yellow fever virus is spread by mosquitoes.

Who is at risk?

Yellow fever virus, and the mosquitoes that spread the virus, are found in certain parts of South America and Africa. Travelers going to these places are at risk for infection with the virus. Check to see if yellow fever vaccine is recommended or required for your destination.

Yellow fever vaccine recommendations in Africa^1,2

View Larger Figure

¹Current as of November 2022. This map is an updated version of the 2010 map created by the Informal WHO Working Group on the Geographic Risk of Yellow Fever.

²Yellow fever (YF) vaccination is generally not recommended for travel to areas where the potential for YF virus exposure is low. Vaccination might be considered, however, for a small subset of travelers going to these areas who are at increased risk for exposure to YF virus due to prolonged travel, heavy exposure to mosquitoes, or inability to avoid mosquito bites. Factors to consider when deciding whether to vaccinate a traveler include destination-specific and travel-associated risks for YF virus infection; individual, underlying risk factors for having a serious YF vaccine-associated adverse event; and country entry requirements.

Yellow fever vaccine recommendations in the Americas^1,2

View Larger Figure

¹Current as of November 2022. This map is an updated version of the 2010 map created by the Informal WHO Working Group on the Geographic Risk of Yellow Fever.

²In 2017, the Centers for Disease Control and Prevention (CDC) expanded its yellow fever vaccine recommendations for travelers going to Brazil because of a large outbreak in multiple states in that country. For more information and updated recommendations, refer to the CDC Travelers’ Health website.

³Yellow fever (YF) vaccination is generally not recommended for travel to areas where the potential for YF virus exposure is low. Vaccination might be considered, however, for a small subset of travelers going to these areas who are at increased risk for exposure to YF virus due to prolonged travel, heavy exposure to mosquitoes, or inability to avoid mosquito bites. Factors to consider when deciding whether to vaccinate a traveler include destination-specific and travel-associated risks for YF virus infection; individual, underlying risk factors for having a serious YF vaccine-associated adverse event; and country entry requirements.

What can travelers do to protect themselves?

Get the yellow fever vaccine and take steps to prevent mosquito bites.

Yellow Fever Vaccine: Requirements and Recommendations

Some countries may require arriving travelers to show proof of yellow fever vaccination. Countries do this as a public health measure to keep travelers from importing the virus. Proof of vaccination requirements may apply to some or all arriving travelers. CDC has no control over other countries’ vaccine requirements or how they are enforced.

Separate from the individual country requirements, CDC makes yellow fever vaccine recommendations for travelers going to countries where there is a risk of yellow fever. CDC recommendations are designed to help keep individuals from getting infected with yellow fever virus during travel.

Check your destination(s) for yellow fever vaccination requirements and recommendations.

Yellow Fever Vaccine: Getting Vaccinated

Visit a yellow fever vaccination clinic. Ask the health care provider at the clinic to confirm if vaccination against yellow fever is required and/or recommended for your destination(s).

Plan to get the vaccine at least 10 days before your travel since proof of vaccination is not valid until 10 days after getting the vaccine, the time needed to develop immunity to yellow fever virus.

A single dose of yellow fever vaccine protects most people for life, but a booster dose after 10 years may be recommended for some travelers. Talk to your health care provider for more information.

In rare cases, yellow fever vaccine can have serious and sometimes fatal side effects. People older than 60 years and people with weakened immune systems might be at higher risk of developing these side effects. Also, there are concerns for the babies of pregnant and nursing women who receive yellow fever vaccine. Before you get vaccinated against yellow fever, discuss your full medical history with your health care provider who can help inform you about the possible risks involved.

Yellow Fever Vaccine: Proof of Vaccination

The International Certificate of Vaccination or Prophylaxis (ICVP, sometimes called the “yellow card”) is your proof that you have been vaccinated against yellow fever. You will receive the ICVP when you get vaccinated. Along with your passport, present the original signed and stamped ICVP (not a photocopy or screenshot) to immigration officials in all countries requiring proof of vaccination.

Prevent mosquito bites:

Use an EPA-registered insect repellent

• Use Environmental Protection Agency (EPA)-registered insect repellents with one of the active ingredients below. When used as directed, EPA-registered insect repellents are proven safe and effective, even for pregnant and breastfeeding women. If also using sunscreen, always apply insect repellent after sunscreen.
  • DEET
  • Picaridin (known as KBR 3023 and icaridin outside the US)
  • IR3535
  • Oil of lemon eucalyptus (OLE)
  • Para-menthane-diol (PMD)
  • 2-undecanone

Find the right insect repellent for you by using EPA’s search tool.

• Insect Repellent Tips for Babies and Children
  • Dress your child in clothing that covers arms and legs.
  • Cover strollers and baby carriers with mosquito netting.
  • When using insect repellent on your child:
    • Always follow label instructions.
    • Do not use products containing oil of lemon eucalyptus (OLE) or para-menthane-diol (PMD) on children under 3 years old.
    • Do not apply insect repellent to a child’s hands, eyes, mouth, cuts, or irritated skin.
      • Adults: Spray insect repellent onto your hands and then apply to a child’s face.

    • If also using sunscreen, always apply insect repellent after sunscreen.

Wear long-sleeved shirts and long pants

Treat clothing and gear with permethrin

• Use 0. 5% permethrin to treat clothing and gear (such as boots, pants, socks, and tents) or buy permethrin-treated clothing and gear.
  • Permethrin is an insecticide that kills or repels insects like mosquitoes and sand flies.
  • Permethrin-treated clothing provides protection after multiple washings.
  • Read product information to find out how long the protection will last.

• If treating items yourself, follow the product instructions.
• Do not use permethrin products directly on skin.
• Watch the CDC video How to Use Permethrin.

Keep mosquitoes out of your hotel room or lodging

• Choose a hotel or lodging with air conditioning or window and door screens.
• Use a mosquito net if you are unable to stay in a place with air conditioning or window and door screens or if you are sleeping outside.

Sleep under a mosquito net

• Sleep under a mosquito net if you are outside or when screened rooms are not available. Mosquitoes can live indoors and bite during the day and night.
• Buy a mosquito net at your local outdoor store or online before traveling overseas.
• Choose a mosquito net that is compact, white, rectangular, with 156 holes per square inch, and long enough to tuck under the mattress.
• Permethrin-treated mosquito nets provide more protection than untreated nets.
  • Permethrin is an insecticide that kills mosquitoes and other insects.
  • To determine if you can wash a treated mosquito net, follow the label instructions.

If you are bitten by mosquitoes, avoid scratching the bites and apply over-the-counter anti-itch or antihistamine cream to relieve itching. See Mosquito Bite Symptoms and Treatment.

If you are bitten by mosquitoes:

• Avoid scratching mosquito bites.
• Apply hydrocortisone cream or calamine lotion to reduce itching.

After Travel

If you traveled and feel sick, particularly if you have a fever, talk to a healthcare provider and tell them about your travel. 

If you need medical care abroad, see Getting Health Care During Travel.

More  Information

• FAQ’s about Yellow Fever
• Avoid Bug Bites-Information for travelers
• Yellow Fever Vaccine Requirements and Recommendations, by Country
• Authorized U.S. Yellow Fever Vaccine Centers
• CDC Yellow Book: Yellow Fever

Yellow fever

Yellow fever

• All topics »
• A
• B
• C
• D
• E
• F
• G
• H
• I
• J
• K
• L
• M
• N
• O
• P
• Q
• R
• S
• T
• U
• V
• W
• X
• Y
• Z
• Resources »
  • Fact sheets
  • Facts in pictures
  • Multimedia
  • Publications
  • Questions & answers
  • Tools and toolkits
• Popular »
  • Air pollution
  • Coronavirus disease (COVID-19)
  • Hepatitis
  • Monkeypox
• All countries »
• A
• B
• C
• D
• E
• F
• G
• H
• I
• J
• K
• L
• M
• N
• O
• P
• Q
• R
• S
• T
• U
• V
• W
• X
• Y
• Z
• Regions »
  • Africa
  • Americas
  • South-East Asia
  • Europe
  • Eastern Mediterranean
  • Western Pacific
• WHO in countries »
  • Statistics
  • Cooperation strategies
  • Ukraine emergency
• All news »
  • News releases
  • Statements
  • Campaigns
  • Commentaries
  • Events
  • Feature stories
  • Speeches
  • Spotlights
  • Newsletters
  • Photo library
  • Media distribution list
• Headlines »
• Focus on »
  • Afghanistan crisis
  • COVID-19 pandemic
  • Northern Ethiopia crisis
  • Syria crisis
  • Ukraine emergency
  • Monkeypox outbreak
  • Greater Horn of Africa crisis
• Latest »
  • Disease Outbreak News
  • Travel advice
  • Situation reports
  • Weekly Epidemiological Record
• WHO in emergencies »
  • Surveillance
  • Research
  • Funding
  • Partners
  • Operations
  • Independent Oversight and Advisory Committee
  • WHO’s Health Emergency Appeal 2023
• Data at WHO »
  • Global Health Estimates
  • Health SDGs
  • Mortality Database
  • Data collections
• Dashboards »
  • COVID-19 Dashboard
  • Triple Billion Dashboard
  • Health Inequality Monitor
• Highlights »
  • Global Health Observatory
  • SCORE
  • Insights and visualizations
  • Data collection tools
• Reports »
  • World Health Statistics 2022
  • COVID excess deaths
  • DDI IN FOCUS: 2022
• About WHO »
  • People
  • Teams
  • Structure
  • Partnerships and collaboration
  • Collaborating centres
  • Networks, committees and advisory groups
  • Transformation
• Our Work »
  • General Programme of Work
  • WHO Academy
  • Activities
  • Initiatives
• Funding »
  • Investment case
  • WHO Foundation
• Accountability »
  • Audit
  • Programme Budget
  • Financial statements
  • Programme Budget Portal
  • Results Report
• Governance »
  • World Health Assembly
  • Executive Board
  • Election of Director-General
  • Governing Bodies website
  • Member States Portal
• Home/
• Newsroom/
• Fact sheets/
• Detail/
• Yellow fever

WHO/E. Soteras Jalil

©
Credits

Key facts

• Yellow fever is an infectious disease transmitted by mosquitoes that bite mostly during the day.
• As of 2023, 34 countries in Africa and 13 countries in Central and South America are either endemic for, or have regions that are endemic for, yellow fever.
• Yellow fever is prevented by a vaccine, which is safe and affordable. A single dose of yellow fever vaccine is sufficient to grant life-long protection.
• A modelling study based on African data sources estimated the burden of yellow fever during 2013 was 84 000–170 000 severe cases and 29 000–60 000 deaths (1).

Overview

Yellow fever is an epidemic-prone mosquito-borne vaccine preventable disease that is transmitted to humans by the bites of infected mosquitoes. Yellow fever is caused by an arbovirus (a virus transmitted by vectors such mosquitoes, ticks or other arthropods) transmitted to humans by the bites of infected Aedes and Haemagogus mosquitoes.

These day-biting mosquitoes breed around houses (domestic), in forests or jungles (sylvatic), or in both habitats (semi-domestic). Yellow fever is a high-impact high-threat disease, with risk of international spread, which represents a potential threat to global health security.

Symptoms

The incubation period for yellow fever is 3 to 6 days. Many people do not experience symptoms. Common symptoms include fever, muscle pain, headache, loss of appetite, nausea or vomiting. In most cases, symptoms disappear after 3 to 4 days.

A small percentage of patients enter a second, more toxic phase within 24 hours of recovering from initial symptoms. High fever returns and several body systems are affected, usually the liver and the kidneys. In this phase, people are likely to develop jaundice (yellowing of the skin and eyes, hence the name yellow fever), dark urine, and abdominal pain with vomiting. Bleeding can occur from the mouth, nose, eyes, or stomach. Half of the patients who enter the toxic phase die within 7–10 days.

Treatment

There is no specific anti-viral drug for yellow fever. Patients should rest, stay hydrated and seek medical advice. Depending on the clinical manifestations and other circumstances, patients may be sent home, be referred for in-hospital management, or require emergency treatment and urgent referral. Treatment for dehydration, liver and kidney failure, and fever improves outcomes. Associated bacterial infections can be treated with antibiotics.

Diagnosis

Yellow fever is difficult to diagnose, especially during the early stages. A more severe case can be confused with malaria, leptospirosis, viral hepatitis, other haemorrhagic fevers, infection with other flaviviruses (such as dengue), and poisoning.

Polymerase chain reaction (PCR) testing in blood can sometimes detect the virus in early stages of the disease. In later stages, testing to identify antibodies is needed (ELISA and PRNT).

Prevention

1. Vaccination

Vaccination is the most important means of preventing yellow fever. The yellow fever vaccine is safe, affordable and a single dose provides life-long protection against yellow fever disease. A booster dose of yellow fever vaccine is not needed.

The vaccine provides effective immunity within 10 days for 80–100% of people vaccinated, and within 30 days for more than 99% of people vaccinated.

Side-effects from the yellow fever vaccine are rare. People who are usually excluded from vaccination include:

• infants aged less than 9 months;
• pregnant women – except during a yellow fever outbreak when the risk of infection is high;
• people with severe allergies to egg protein; and
• people with severe immunodeficiency due to symptomatic HIV/AIDS or other causes, or who have a thymus disorder.

In accordance with the International Health Regulations (IHR), countries have the right to require travellers to provide a certificate of yellow fever vaccination. If there are medical grounds for not getting vaccinated, this must be certified by the appropriate authorities.

• Countries with risk of yellow fever transmission and countries requiring yellow fever vaccination (November 2022) (who.int)
• Vaccination requirements and recommendations for international travellers; and malaria situation per country – 2022 edition (who.int)

2. Vector control

The risk of yellow fever transmission in urban areas can be reduced by eliminating potential mosquito breeding sites, including by applying larvicides to water storage containers and other places where standing water collects.

Preventive measures, such as wearing clothing to minimize skin exposure and repellents are recommended to avoid mosquito bites. The use of insecticide-treated bed nets is limited by the fact that Aedes mosquitos bite during the daytime.

Both vector surveillance and control are components of the prevention and control of vector-borne diseases, especially for transmission control in epidemic situations. For yellow fever, vector surveillance targeting Aedes aegypti and other Aedes species will help inform where there is a risk of an urban outbreak.

3. Epidemic preparedness and response

Prompt detection of yellow fever and rapid response through emergency vaccination campaigns are essential for controlling outbreaks. However, underreporting is a concern; WHO estimates the true number of cases to be 10 to 250 times what is now being reported.

WHO recommends that every at-risk country has at least one national laboratory where basic yellow fever blood tests can be performed.  A confirmed case of yellow fever in an unvaccinated population is considered an outbreak. A confirmed case in any context must be fully investigated. Investigation teams must assess and respond to the outbreak with both emergency measures and longer-term immunization plans.

WHO response

The Eliminate Yellow Fever Epidemics (EYE) Strategy was developed in response to two urban yellow fever outbreaks – in Luanda (Angola) and Kinshasa (Democratic Republic of the Congo), with international exportation to other countries, including China, showing that yellow fever poses a serious global threat requiring new strategic thinking.

The EYE strategy is comprehensive, multi-component and multi-partner. In addition to recommending vaccination activities, it calls for building resilient urban centres, planning for urban readiness, and strengthening the application of the International Health Regulations (2005).

To find out more about the EYE Strategy, click here: Eliminate yellow fever epidemics (EYE) strategy 2017-2026 (who.int)

It is expected that by the end of 2026, almost 1 billion people will be protected against yellow fever through vaccination.

 

References

1. Garske T. et al. Yellow fever in Africa: Estimating the burden of disease and impact of mass vaccination from outbreak and serological data. PLoS Med. 2014;11(5):e1001638 – https://pubmed.ncbi.nlm.nih.gov/24800812/

Related links

General information

• Q&A: Yellow fever
• International Coordinating Group on Vaccine Provision
• Q&A: Fractional doses of the yellow fever vaccine

Technical information

• WHO’s work on yellow fever
• Situation reports

Yellow fever: description, prevention, treatment

This virus is carried by the yellow fever mosquito (Aedes Aegypti species), this species is especially common in Latin America, South America and Africa.

Despite the fact that the yellow fever vaccine was invented 60 years ago, epidemics in Africa still occur from time to time due to insufficient immunization in cities.

• What is yellow fever?
• Symptoms of yellow fever
• Where is yellow fever common?
• Treatment of yellow fever

---

Yellow fever

If you are going to a sub-Saharan African country, it is better to take care of vaccination. Prevention of this disease is very important, as it can lead to hepatitis and seriously damage your liver. In fact, the main symptoms of yellow fever – jaundice and fever – come from the fact that the virus damages the liver. This disease can lead to other damage to internal organs, and even fatal ones, so taking safety measures is a matter of life and death.

What is yellow fever? Understanding the Virus

Yellow fever is a viral infection that causes damage to organs, especially the liver. About 200,000 cases are registered annually, 30,000 of which die. The number of cases has recently increased dramatically, due to the fact that cities are growing, the climate is changing, but the immunization of the population is often low. According to WHO, in Latin America the risk of contracting yellow fever is the highest in the world.

So what causes yellow fever? Most often it is transmitted by infected mosquitoes through a bite.

How is yellow fever transmitted?

In most cases, people become infected with yellow fever when they are bitten by an infected mosquito. The virus can also be transmitted directly through an infected person, through dirty needles, for example. Otherwise, this disease is not transmitted from person to person.

Symptoms of yellow fever

Some infected people do not develop symptoms of yellow fever. Usually the infection has 3 stages. The first begins a few days after the mosquito bite and may include the following symptoms:

• Headache
• Dehydration
• Pain in muscles and joints
• Back pain
• Loss of appetite
• Vomiting
• Cold-like symptoms
• Heat
• Chills

After the initial phase, most patients get better, and often the disease does not progress further. However, in about 15-25% of patients, the condition worsens again and moves to the third, more serious stage. During this phase, the following symptoms may appear:

• High heat
• Dehydration
• Internal bleeding
• State of shock
• Bleeding from eyes, mouth and nose
• Bloody stool
• Hematemesis
• Jaundice – yellowing of the skin and eyes
• Redness of the tongue, eyes and face
• Inflammation of the liver or hepatitis
• Multiple organ failure
• Seizures
• Coma
• Death

These symptoms of viral hemorrhagic fever, it damages the internal organs and circulatory system. This condition is life-threatening for the patient. About half of patients with the third stage of yellow fever do not survive.

But those who survive will need lifelong medical care, because some of the organs, including the heart, lungs, kidneys or liver, can be seriously damaged. Patients with kidney damage may require lifelong hemodialysis. If your heart is affected by yellow fever, you will need to take medications or other treatments on a regular basis to prevent heart failure or a heart attack. Even when yellow fever recedes, the patient’s life can change dramatically.

---

Where is yellow fever common?

Yellow fever is more common in Africa and in Central and South America. These areas are endemic for yellow fever. In West Africa and South America, its prevalence is especially high. According to the Centers for Disease Control and Prevention, among those who have not been vaccinated and have been in West Africa for only 2 weeks, 50 out of 100,000 become infected with yellow fever. Among people who spent a two-week vacation in South America, 5 out of 100,000 become infected.

Countries with particularly high prevalence of yellow fever:

• Benin
• Cameroon
• Republic of the Congo
• Ivory Coast
• Burkina Faso
• Ghana
• Gabon
• Guiana
• Central African Republic
• Liberia
• Mali
• Angola
• Niger
• Rwanda
• Democratic Republic of the Congo
• Sao Tome and Principe
• Togo

In addition to these countries, some sub-Saharan African countries, as well as countries in Central and South America, can be added to this list. Urban dwellers are more susceptible to the virus. In Russia, all cases of yellow fever are imported. In our country, this infection has been known for a long time. Back in 1805, a decree would have been issued with its description and information about the need to protect port cities from this disease. The largest epidemic of yellow fever in Russia was during the construction of the Panama Canal, then 500 thousand people fell ill.

How do you know if you have yellow fever?

The only way to know that you have contracted yellow fever is to visit a doctor. If you have been to a country where the condition is common and then develop a fever or other symptoms, see your doctor right away. The doctor will clarify the symptoms and conduct tests for yellow fever. Tests may also be done to check for damage to the liver or other organs. When the first symptoms appear, it is important to immediately consult a doctor, because without treatment, a fever can lead to irreparable consequences.

Treatment of yellow fever

There is no cure as such, if only symptomatic therapy, and the latter must be timely. If you are affected by this virus, doctors will advise you to be hospitalized so that it is easier to monitor your symptoms and provide assistance depending on the condition.

For example, you may be given medication to reduce fever and muscle pain, and may be given an IV to treat dehydration. If you regularly take anti-inflammatory medications that thin your blood, such as aspirin, you will need to stop taking them. Such medicines increase the risk of internal bleeding in this disease. If your condition worsens due to organ damage, doctors at the hospital can help you.

---

Yellow fever vaccination

Since there is no cure for this virus, it is important to get a yellow fever vaccination before traveling to a high-risk country. Moreover, to enter some countries, you will need an International Vaccination Certificate with a yellow fever vaccination record.

As with any vaccine, the yellow fever vaccine has side effects. This vaccine is live, so it carries more risks than inactivated vaccines. Some patients develop cold-like symptoms, while others may develop severe allergic reactions. Sometimes the vaccine develops reactions that threaten the life of the patient. If your condition changes after vaccination, contact your doctor immediately.

Remember that no vaccine is 100% effective. Some vaccinated people can still contract yellow fever.

As a general rule, doctors recommend that all travelers older than 9 months who go to countries where yellow fever is endemic must be vaccinated. However, to avoid serious side effects, you should consult your doctor before vaccination if:

• You have immune system problems due to HIV or another condition
• You are undergoing treatment for cancer or any other treatment that is difficult for the body
• You have cancer or are in remission
• Have problems with your thymus
• You are 65 or older
• You need to vaccinate a child under 9 months old
• You have had an allergic reaction to the yellow fever vaccine or any other vaccinations
• You are allergic to gelatin, chicken or eggs
• You are pregnant or about to become pregnant
• You are breastfeeding

If your doctor thinks that you should not be vaccinated against yellow fever because the risk of serious side effects is too high, it is better to reconsider your plans. If you still need to travel to a country with a high risk of contracting this virus, you may need a contraindication entry on your international vaccination certificate, and some countries may simply not let you in.

How long does a yellow fever vaccine last?

The vaccine becomes active after about 10 days, and most doctors recommend vaccination at least 10 days before travel. Some doctors advise getting vaccinated at least a month in advance so that all possible side effects from the vaccine go away. Additional recovery time may be needed even if you only have cold-like symptoms after vaccination. It is better to stay at home and recover, otherwise all the pleasure of traveling may come to naught.

The yellow fever vaccine lasts 10 years, so no matter how often you travel to countries where this disease is common, you will need to be vaccinated every 10 years. If you want to know more about the risk of infection and the side effects of vaccination, it’s best to talk to your doctor.

Prevention of yellow fever

How to avoid contracting yellow fever while traveling? The best prevention is to avoid mosquito bites. The following tips will help protect you:

• Use repellents. The most effective are those that contain DEET, IR3535, picaridin, lemon and eucalyptus oil. Always check the expiration date and follow the directions carefully.
• Apply repellant to clothes, tent, mosquito nets on hotel windows, and any other mosquito nets.
• Be sure to use mosquito nets on the windows of the place where you are going to live. Check nets regularly for damage.
• Spray all mosquito nets with repellent at night. This will further protect you.
• Wear long sleeves and long pants. Cover your skin as much as possible so mosquitoes don’t have a chance to bite. It is better to choose clothes in light shades. Mosquitoes perceive light colors worse, in addition, such clothes will protect you from overheating.
• At dawn and dusk, avoid walking in areas with a high number of mosquitoes. It is at this time of day that these insects are most active.

It is almost impossible to avoid all mosquito bites, write down all your trips in a special journal and register all insect bites that you notice on yourself. If you develop any unusual symptoms, these notes will help doctors make a proper diagnosis.

Long-term solutions to mosquitoes

Most people get yellow fever through mosquito bites. If you reduce the number of mosquitoes around you, you will significantly reduce the risk of bites and infection. Despite the fact that there are no natural foci of yellow fever in Russia, travelers often return from endemic areas infected with this virus or other diseases. Native mosquitoes can carry diseases from these travelers to healthy people.

In addition to yellow fever, the yellow fever mosquito can also transmit dengue and chikungunya. If there are mosquitoes on your property, you are at risk of getting infected. Yellow fever prevention should start with reducing the mosquito population in your yard.

The best method of protection is to reduce the number of mosquitoes around you. If you want to reduce the risk of biting and contracting diseases, there are several steps you can take to reduce your mosquito population.

The very first and easiest step is to reduce the number of mosquito breeding areas. These insects like to lay their eggs in damp and warm places. For the appearance of thousands of eggs and larvae, a lake, a pond and any (even minimal) amount of standing water is enough. Such places, as well as shady areas, can be eliminated on your site. Particular attention should be paid to:

• standing water tire
• Bird drinkers
• Ditches and ditches
• Still water in flower pots and other containers
• Rain barrels
• Long grass

In some cases it may not be possible to dispose of standing water. For example, you may not be able to remove a swimming pool from a neighbor’s lot or drain a swamp in the area. In this case, mosquito traps can help.

Traps serve to reduce the mosquito population (especially when the site is surrounded by a high impenetrable fence), they catch the females. It is the females who drink blood, they need it for laying eggs. After a few weeks of operation of the trap, a decrease in the number of mosquitoes will be noticeable. The World Health Organization notes that the most effective prevention of yellow fever is mosquito control.

Use Mosquito Magnet traps to reduce mosquitoes

You do not need any complex systems to reduce the number of bloodsuckers near your home. Mosquito Magnet traps emit heated and humidified carbon dioxide along with an additional attractant. When mosquitoes approach the trap, they are sucked in, where they dry out and die. It is a safe alternative to chemical sprays.

If you combine Mosquito Magnet traps with repellents and standing water killer, then the number of mosquitoes in your yard will be critically reduced (especially if your yard is surrounded by a high enough fence). Isn’t it great to enjoy a summer vacation without mosquito bites? Not only will you protect yourself from those nasty itchy blisters, but you won’t catch vector-borne diseases either.

---

Protect
your family, pets and guests from mosquito-borne diseases
trap Mosquito Magnet – long,
scientifically proven solution.

Yellow fever – Features of the disease

07/08/2022

“By the way, why is it called yellow?” asked another traveler who was going to Togo. He was faced with the need to be vaccinated against the yellow fever virus, because when entering the country it is necessary to provide proof of vaccination – a vaccination certificate.

Obviously, yellow fever is called yellow fever because jaundice can develop, but believe me, this is not the worst thing that can happen.

Today we will analyze it in detail, but first we will complain that if there were no requirement in Togo and in a number of other countries to confirm the need for confirmation of vaccination, the traveler would simply not come without knowing what other vaccines need to be done before the trip, what to collect in a first aid kit and how to protect yourself from tropical malaria, another potentially deadly disease.

Virus encounter

The tropical regions of Central and South America, as well as the countries of Africa, are endemic for yellow fever, that is, it is quite possible to get sick.

Transmission of the virus to humans occurs through the bite of a mosquito, which about 2 weeks ago became infected from a sick person. Transmission is also possible through the bite of forest mosquitoes, which carry the virus from wild primates. Infection rates peak during the heavy rainy season in South America and during the late rainy seasons in Africa.

The incubation period (the period from infection to the development of symptoms) can be 3 to 6 days. During this period, high viremia is usually observed – a large amount of virus in the blood. It is during this period that a mosquito can become infected from a sick person when bitten.

Yellow fever symptoms

The disease begins suddenly, with an increase in body temperature up to 39-40C, headache / dizziness and muscle pain. Then nausea, vomiting appear, weakness, anxiety, irritability increase.

Another characteristic symptom is bradycardia against the background of fever, which develops at the second stage of the disease (Fage’s symptom). After a few days, remission sets in – the symptoms disappear. At this time, some patients can recover. But in 15–25% of patients, symptoms recur and can progress to death.

In the stage of relapse are noted:

• heat;
• stomach ache;
• kidney failure;
• vomit;
• enlargement of the liver and spleen;
• development of jaundice;
• bleeding from mucous membranes;
• hemorrhagic rash.

As the disease progresses, multiple organ failure develops. If the kidneys and liver are involved, the risk of death reaches 50%. Death occurs 7–10 days after the onset of symptoms.

Disease diagnosis

Mild forms of infectious disease are often not diagnosed. But the diagnosis of yellow fever should be ruled out if the patient develops jaundice, fever, and bradycardia.

Characteristic deviations can be detected in general clinical and biochemical blood tests, in a coagulogram and in a general urinalysis. Specific diagnostics is based on PCR diagnostics – the search for the genetic material of the virus in biological material. It is very important to test specimens within the first 10 days of disease onset, when the sensitivity of the tests is higher.

Serological diagnostics is also used, that is, ELISA (determination of antibodies), but there may be cross-over, and therefore false-positive, results with other flaviviruses, which makes interpretation difficult. After 7-10 days, the sensitivity of class M antibodies is 95%. A confirmed case is considered to be a clinically similar case + a four-fold increase in antibody titer in paired sera with the exclusion of cross-reactivity with other flaviviruses.

Yellow fever treatment

There is currently no specific antiviral treatment for yellow fever. Supportive therapy is of great importance, which consists in stopping bleeding, maintaining pressure, replenishing fluid, if necessary, performing hemodialysis, and antibiotic therapy for secondary complications.

But the disease can be prevented with an extremely effective vaccination. The vaccine is affordable and safe.

As with any other vaccine, within 2-3 days after vaccination against yellow fever, a post-vaccination reaction may develop: slight redness and swelling at the injection site, slight malaise. In 5-10% of those who received the vaccine, 4-10 days after vaccination, chills, fever up to 38.5 C, malaise, headache, which can last a couple of days and are well stopped by taking NSAIDs – non-steroidal anti-inflammatory drugs, may occur.

One dose of the vaccine is sufficient to form lifelong immunity against yellow fever virus in more than 80% as early as 10 days after vaccination, and in more than 99% within 30 days after vaccination. Therefore, it is necessary to be vaccinated at least 10 days before entering the endemic territory, not to mention the fact that the date of commencement of the validity of the international certificate with vaccination against yellow fever is + 10 days from the day of the vaccine.

10 days is a minimum, but it is still better to prepare in advance and consistently. At H-clinic, we help patients create an individual travel vaccination schedule based on the time available, the area the patient is traveling to, and the risks that may be there. In addition, we give recommendations on collecting a first-aid kit and non-specific prevention of other diseases (for example, parasitic diseases that can be contracted when swimming in water bodies).

and most importantly, many areas endemic for yellow fever are also endemic for malaria. Depending on the length of stay in the dangerous territory, concomitant diseases, the predominance of certain types of Plasmodium and their possible resistance to drugs, we select the most adequate and convenient regimen for chemoprophylaxis of malaria. Even in the last hours before departure, you can always find out what you can do if you did not prepare for the trip in advance, or the need to fly arose suddenly.