Keystone virus (Keystone orthobunyavirus) is a mosquito-borne virus which can infect mammals. It was first discovered in animals in the Florida area, where it is spread in part by local species of Aedes mosquitoes. In 1964, a case of human infection, producing minor symptoms of a rash and fever, was circumstantially diagnosed. Conclusive laboratory demonstration of the virus in humans was first obtained and reported in 2018.