Jamestown Canyon virus (JCV, not to be confused with John Cunningham virus that bears the same initials) is an orthobunyavirus of the California serogroup transmitted during the summer by different mosquito species in the United States and Canada. The virus is one of a group of mosquito-borne or arthropod-borne viruses, also called arboviruses, that can cause fever and meningitis or meningoencephalitis, mostly in adults. Jamestown Canyon virus disease is relatively rare; in the United States, the CDC found only 31 disease cases from 2000-2013, but it is likely under-recognized and probably endemic throughout most of the United States.