Yellow fever is a viral disease transmitted between humans by mosquitoes but is noncontagious. Yellow fever is known for effecting humans, but also effect monkeys and other animals. The disease occurs only in parts of Africa and South America. But there are only some countries in Africa and South America that have endemic Yellow Fever. In South America the countries are Panama, Columbia, Venezuela, Suriname, Western Ecuador, Guyana, French Guyana, Western Peru, Western Bolivia, and Eastern Brazil. In Africa the countries consist of Angola, Tanzania, Zaire, Kenya, Uganda, Somalia, Ethiopia, southern Sudan, southern Sudan, southern Chad, southern Niger, southern Mali, Central African Republic, Congo, Gabon, Rio Muni, Cameroon, Nigeria, Benin, Togo, Ghana, Burkino Faso, Ivory Coast, Liberia, Sierra Leone, Guinea, Guinea-Bissau, Gambia, Senegal, Sao Tome and Principe Islands.
In these countries sporadic infections occur almost exclusively to forestry and agricultural workers who are exposed occupationally in or near forests. In Africa the virus is transmitted in three geographic regions. The moist savanna zones of West and Central Africa during the rainy season, urban locations and villages in Africa, and lastly in jungle regions.
Symptoms of the disease range from fever, chills, and headache to abdominal pain, vomiting of blood, hemorrhage from mucous membranes, and jaundice. There may appear to be a brief recovery before the disease progresses to more severe complications after the fifth day, including internal bleeding, kidney or liver failure, and degeneration of the heart. the deterioration of the liver cells results in yellow pigmentation on the skin which gives this disease it's name. The incubation period of the disease ranges from 3-6 days. Death occurs in about 5% of those infected. But on the good side like many other diseases, once you've had it you'll never get it again.
While in these countries the General precautions to avoid mosquito bites should be followed. These include the use of insect repellent, protective clothing, and mosquito netting. These mosquitoes bite mainly during the evening and morning hours.
Although yellow fever is a very rare cause of illness in travelers, most countries require a certificate from travelers arriving from infected areas. Some countries in Africa require evidence of vaccination from all entering travelers. Vaccination is also recommended for travel outside the urban areas of countries which do not officially report the disease, but which lie in the yellow fever endemic zone. Other countries require an individual, even only in transit, to have a valid International Certificate of Vaccination if he or she has been in countries either known or thought to harbor Yellow Fever virus. Such requirements may be strictly enforced, particularly for persons traveling from Africa or South America to Asia.
The Yellow fever vaccine is a live virus vaccine that was created in 1937 by a south african physician named Max Theiler. A single dose confers long-lived immunity lasting 10 years or more. This vaccine has been used for several decades and has a very low rate of adverse reactions associated with it. After immunization an International Certificate of Vaccination is issued and is valid 10 days after vaccination to meet entry and exit requirements
for all countries. One dose of yellow fever vaccine may be administered to adults and children over 9 months of age. This vaccine is only administered at designated yellow fever centers, usually your local health department.
Travelers who have a medical reason not to receive the yellow fever vaccine should obtain a medical waiver. Most countries will accept a medical waiver for persons with a medical reason not to receive the vaccine. In such cases, obtain the waiver in writing from consular or embassy officials before departure. A physician's letter clearly stating the medical reason not to receive the vaccine might be acceptable to some governments. It should be written on letterhead stationery and bear the stamp used by a health department or official immunization center to validate the International Certificate of Vaccination.