An acute systemic (bodywide) illness caused by a virus called a flavivirus. In severe cases, the viral infection causes a high fever, bleeding into the skin, and necrosis (death) of cells in the kidney and liver. ... The virus of yellow fever is transmitted in most cases by a bite of a mosquito.
Mild cases cause fever, headache, nausea and vomiting. Serious cases may cause fatal heart, liver and kidney conditions.
The flavivirus causes yellow fever, and it's transmitted when an infected mosquito bites you. Mosquitoes become infected with the virus when they bite an infected human or monkey. The disease cannot be spread from one person to another.