Yellow fever is caused by a virus that is found in Africa and South America.

The virus belongs to a group of viruses called flaviviruses. Other flaviviruses cause disease in people, including dengue, West Nile, St. Louis encephalitis, and Japanese encephalitis.

It is primarily spread to people through the bite of infected mosquitoes. The virus is maintained in the environment between mosquitoes and non-human primates, like monkeys.

People can become infected with the virus when mosquitoes feed on infected primates (e.g., other people or monkeys) and then bite them.

TRANSMISSION: Yellow fever virus is transmitted to humans through a bite of infected Ae. aegypti mosquito. This mosquito is found in Florida and also serves as the vector for dengue and chikungunya. While the yellow fever virus is not is not circulating in North America, the risk of introduction is possible due to international travel.

SYMPTOMS: After becoming infected, the incubation period of yellow fever is usually 3-6 days.

Illness ranges in severity from a self-limited febrile illness to severe hepatitis and hemorrhagic fever. Symptoms of severe infection are high fever, chills, headache, muscle aches, vomiting, and backache. 

After a brief recovery period, the infection can lead to shock, bleeding, and kidney and liver failure. Liver failure causes jaundice, the yellowing of the skin and the whites of the eyes. Severe infections can be fatal.

TREATMENT: There is no specific treatment, only supportive care and treatment of symptoms. Aspirin and other non-steroidal anti-inflammatory drugs (such as ibuprofen and naproxen) should be avoided because these may increase the risk for bleeding.

PREVENTION: Yellow fever is a rare cause of illness in U.S. travelers to endemic countries. Vaccination is the most important preventive measure against yellow fever. The vaccine confers sustained immunity and life-long protection against yellow fever disease without the need for a booster. The vaccine provides effective immunity within 30 days for 99% of persons vaccinated.

FOR MORE INFO, visit Yellow Fever Virus - Florida Department of Health.