Chikungunya virus cause a infection named Chikungunya. The disease is characterized by the sudden onset of fever two to four days after exposure, while accompanying joint pains typically last weeks or months but sometimes years. The mortality rate is a little less than 1 in 1,000; the elderly or those with underlying chronic medical problems are most likely to have severe complications. The virus is passed to humans by two species of mosquito of the genus Aedes: A. albopictus and A. aegypti. Animal reservoirs of the virus include monkeys, birds, cattle, and rodents.