Yellow fever, known historically as yellow jack, yellow plague, or bronze john, is an acute viral disease. In most cases, symptoms include fever, chills, loss of appetite, nausea, muscle pains particularly in the back, and headaches. Symptoms typically improve within five days. In some people within a day of improving, the fever comes back, abdominal pain occurs, and liverdamage begins causing yellow skin. If this occurs, the risk of bleeding and kidney problems is also increased.
The disease is caused by the yellow fever virus and is spread by the bite of the female mosquito. It infects only humans, otherprimates, and several species of mosquitoes. In cities, it is spread primarily by mosquitoes of the Aedes aegypti species. The virus is an RNA virus of the genus Flavivirus. The disease may be difficult to tell apart from other illnesses, especially in the early stages. To confirm a suspected case, blood sample testing with polymerase chain reaction is required.
A safe and effective vaccine against yellow fever exists and some countries require vaccinations for travelers. Other efforts to prevent infection include reducing the population of the transmitting mosquito. In areas where yellow fever is common and vaccination is uncommon, early diagnosis of cases and immunization of large parts of the population is important to prevent outbreaks. Once infected, management is symptomatic with no specific measures effective against the virus. In those with severe disease, death occurs in about half of people without treatment.
Yellow fever causes 200,000 infections and 30,000 deaths every year, with nearly 90% of these occurring in Africa. Nearly a billion people live in an area of the world where the disease is common. It is common in tropical areas of South America and Africa, but not in Asia. Since the 1980s, the number of cases of yellow fever has been increasing. This is believed to be due to fewer people being immune, more people living in cities, people moving frequently, and changing climate. The disease originated in Africa, where it spread to South America through the slave trade in the 17th century. Since the 17th century, several major outbreaks of the disease have occurred in the Americas, Africa, and Europe. In the 18th and 19th centuries, yellow fever was seen as one of the most dangerous infectious diseases. The yellow fever virus was the first human virus discovered.