DefinitionYellow fever is a viral infection transmitted by mosquitoes.Causes, incidence, and risk factorsYellow fever is caused by a small virus that is spread by the bite of mosquitoes. This disease is common in South America and in sub-Saharan Africa.Anyone can get yellow fever, but the elderly have a higher risk of severe infection. If a person is bitten by an infected mosquito, symptoms usually develop 3 - 6 days later.Yellow fever has three stages:Early stage: Headache, muscle and joint aches, fever, flushing, loss of appetite, vomiting, and jaundice are common. After approximately 3 - 4 days, often symptoms go away briefly (remission).Period of remission: After 3 - 4 days, fever and other symptoms go away. Most people will recover at this stage, but others may move onto the third, mo