Yellow Fever

What is Yellow Fever?

Yellow fever virus -- found in South America and Africa -- is a very rare cause of illness in U.S. travelers, ranging in severity from a mild fever to severe liver disease with bleeding.

How is Yellow fever transmitted?

Yellow fever virus is transmitted to people primarily through the bite of infected Aedes or Haemagogus species mosquitoes. It is related to West Nile, St. Louis encephalitis and Japanese encephalitis viruses.

What are the symptoms?

The majority of persons infected with yellow fever virus have no illness or only mild illness. In persons who develop symptoms, the time from infection until illness is typically three to six days. Initial symptoms include sudden onset of fever, chills, severe headache, back pain, general body aches, nausea, vomiting, fatigue and weakness. Most persons improve after the initial presentation. After a brief remission of hours to a day, roughly 15 percent of cases progress to develop a more severe form of the disease.

What are the complications from this disease?

The majority of infected persons will have mild disease with complete recovery. In persons who become symptomatic but recover, weakness and fatigue may last several months. The severe form is characterized by high fever, jaundice and bleeding. It can lead to shock and failure of multiple organs. Roughly 20-50 percent of people who develop severe illness may die.