Yellow fever is caused by a virus transmitted by mosquitoes. It is typically found in tropical and subtropical areas in Africa and South America. Yellow fever is a rare cause of illness among U.S. travelers.
About 3 to 6 days after being bitten by an infected mosquito, the individual develops symptoms including headache, fever, joint aches, vomiting, and jaundice. After 3 to 4 days, the person may go into remission; many people recover at this stage. But within 24 hours, about 15 percent of infected individuals develop symptoms of a more severe form of the disease. These include high fever, jaundice, bleeding, and eventually shock and organ failure. Among those who develop severe disease, 20 to 50 percent may die.
Although there is no treatment for the virus, many of the symptoms can be addressed. Rest, fluids, and use of medication to reduce the fever can help. However, aspirin or other nonsteroidal anti-inflammatory drugs, such as ibuprofen, should not be used because they may increase the risk of bleeding.
A vaccine for yellow fever is available, and it offers the best protection against the virus. The vaccine—a live, weakened strain of the virus—is given as a single shot. For people who remain susceptible, the shot should be given every 10 years. Other precautions that can be taken include sleeping in screened areas to avoid contact with mosquitoes, using mosquito repellants, and wearing clothing that fully covers the body.