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Yellow Fever

Yellow fever is an infection caused by the yellow fever virus that can manifest in a variety of ways; ranging from a mild flu like disease that resolves quickly to severe liver disease progressing to multiple organ failure, hemorrhage and death and is spread by mosquitoes.

What is the International Certificate of Yellow Fever Vaccination?

To decrease the spread of the yellow fever virus, a concerted effort has been made to vaccinate people traveling to and from yellow fever prevalent countries. Many countries require that you provide proof of yellow fever vaccination for entry. That proof is the universally accepted International Certificate of Yellow Fever Vaccination.

For a list of the authorized vaccine and vaccine certificate providers please go to vaccine providers or check with your local state or county health department.

If the vaccine is contraindicated for the reasons listed before, a waiver can be signed by the authorized providers listed at the above web site.

The following countries in Africa require proof of yellow fever vaccination from ALL travelers:

 Angola, Benin, Bolivia, Burkina Faso, Burundi, Cameroon, Central Africa Republic, Congo, Cote de' Ivoire, Democratic Republic of the Congo, French Guiana, Gabon, Ghana, Liberia, Mali, Niger, Rwanda, Sao Tome & Principe, Sierra Leone, Togo.  

Many countries require proof of yellow fever vaccination IF arriving FROM countries where yellow fever is present, EVEN if you were only there in transit.

The following is a list of countries where yellow fever is prevalent:

Africa: Angola, Benin, Burkina Faso, Burundi, Cameroon, Central African Republic, Chad, Congo, Cote d' Ivoire, Democratic Republic of Congo, Equatorial Guinea, Ethiopia, Gabon, Gambia, Ghana, Guinea, Guinea Bissau, Kenya, Liberia, Mali, Mauritania, Niger, Nigeria, Rwanda, Sao Tome & Princpe, Senegal, Sierra Leone, Somalia, Sudan, Tanzania, Togo, Uganda.

South America: Argentina, Bolivia, Brazil, Colombia, Ecaudor, French Guiana, Guyana, Paraguay, Peru, Suriname, Venezuela.

Central America: Panama

Carribean: Trinidad & Tabago

Please search by the specific country that you are traveling to for their specific yellow fever vaccination and certificate requirement.

Where does it occur?

The disease occurs mainly in tropical parts of Africa, South and Central America. Map

How is it transmitted?

The yellow fever virus is transmitted through the bite of mosquitoes, mainly the aedes aegypti mosquitoes. These mosquitoes bite during daylight hours. The highest incidence is during the rainy season when mosquito populations are high: July-Oct in Africa and Jan-March in South & Central America.

Is it contagious from person to person?

It is not contagious from person to person.

What is the risk for travelers?

For an unvaccinated traveler going to a high risk area for 2 weeks the risks of illness and death have been estimated as follows:

Africa: Illness - 1:2000 Death – 1:10,000

South & Central America: Illness- 1:20,000 Death – 1:100,000

The risks are highest during the rainy season and for visits to rural and forest areas below 8000 feet (2500 m)

How soon after exposure will one develop symptoms?

Symptoms usually develop 3-6 days after exposure

What are the signs and symptoms?

Typically, the illness starts with onset of fever, chills, headache, backache, muscle pains, nausea and vomiting. One helpful clue is that the heart rate maybe slower than expected for the degree of high fever. Most people recover from their illness at this point.

However in 15-30% of people, after seeming to get better, in a few days there is relapse of fever and rapid progression to jaundice, multiple organ failure, hemorrhage from gums, nose and intestinal tract leading to death in nearly 50% of this group.

Is there any treatment?

There are no specific anti-viral medications; supportive treatment and if needed care in the intensive care setting is the mainstay.

Are there any lab tests to diagnose illness?

The virus can be isolated from blood by culture or PCR method. Other blood antibody and ELISA tests are also available.

What preventive measures can be taken?

A single injection of the yellow fever vaccine assures protection for approximately 10 years.

 The vaccine needs to be produced by an authorized manufacturer and there are specific yellow fever vaccine providers; go to: vaccine providers or contact your local state or county health department.

Travelers should also take adequate insect safety measures as follows:

Stay in accommodations with screens, or air-conditioning

Use Permethrin impregnated mosquito nets

Wear long sleeve shirts, pants and socks

Apply insect repellant containing DEET to clothing and exposed skin

What are the issues with yellow fever vaccine?

The vaccine has side-effects and the risks versus benefit need to be carefully evaluated by you and your physician.

The vaccine uses a live virus grown in chicken embryo and is therefore contraindicated in:

Pregnant and breast feeding individuals

Children less than 9 months of age

Individuals who are allergic to eggs

Individuals with compromised immune system (transplant patients/cancer patients/patients on prednisone or immunosuppressive medications etc.)

HIV positive individuals with a CD4 count less than 400

The vaccine is associated with the following serious side effects:

neurologic disease – Encephalitis, Guillan-Barre Syndrome 4 - 6 cases per 1 million doses of vaccine

viscerotropic disease – Illness similar to actual yellow fever with multiorgan failure 3 – 5 cases per 1 million doses of vaccine

Individuals at higher risk for these side effects are

age greater than 60 years or less than 9 months

history of thymus disease (myasthenia gravis, thymoma, thymectomy)

severe immunocompromise.

Mild adverse reactions like headache, muscle pain, low grade fever, arm pain etc. can occur as well.

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