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Yellow Fever

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A transmission electron microscopic (TEM) image of yellow fever virus virions (CDC/Erskine Palmer)

What is yellow fever?

Yellow fever is a virus transmitted by the bite of an infected mosquito. It has been found in areas of South America and Africa.

What are the signs and symptoms of yellow fever?

Symptoms of yellow fever usually begin 3-6 days after infection, and include fever, chills, severe headache, back pain, body aches, nausea and vomiting, fatigue, and weakness. These are rarely followed by a more severe form of yellow fever, including jaundice, bleeding, high fever, and organ failure.

How can I get yellow fever ?

Yellow fever is transmitted through the bite of an infected mosquito. It cannot be transmitted directly from person to person.

Can I get yellow fever in San Mateo County?

Yellow fever is not currently present among mosquitoes in San Mateo County. The species of mosquito capable of transmitting yellow fever, Aedes aegypti, has not been found in San Mateo County recently. Local mosquitoes could become infected by feeding on someone with an active case of yellow fever . For this reason, the District works closely with the County Health Department on all mosquito-borne disease cases. When a mosquito-borne disease is detected in a patient in San Mateo County, the health department notifies the District. District staff will then conduct mosquito surveillance in the area to ensure that vector mosquitoes are kept at very low numbers.

What can I do if i am traveling to a country that has yellow fever?

A vaccine is available for yellow fever. Travelers are also advised to avoid mosquito bites. For information on protecting yourself from mosquito bites, see What You Can Do: Mosquitoes.

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