Yellow fever is a viral disease of typically short duration. The disease is caused by the yellow fever virus and is spread by the bite of an infected female mosquito. It infects humans, other primates and several species of mosquitoes. In cities, it is spread primarily by Aedes aegypti, a type of mosquito found throughout the tropics and subtropics. Aedes aegypti also transmits the viruses that cause dengue fever, West Nile fever, 
In areas where yellow fever is common and vaccination is uncommon, early diagnosis of cases and immunisation of large parts of the population is important to prevent outbreaks. Death occurs in up to half of those who get severe disease.
Treatment
No specific treatments have been found to benefit patients with yellow fever. Whenever possible, yellow fever patients should be hospitalised for supportive care and close observation. Treatment is symptomatic. Rest, fluids, and use of pain relievers and medication to reduce fever may relieve symptoms of aching and fever. Yellow fever patients should be protected from further mosquito exposure (staying indoors and/or under a mosquito net) for up to 5 days after the onset of fever.