Keystone Virus Isolated From a Florida Teenager With Rash and Subjective Fever: Another Endemic Arbovirus in the Southeastern United States?

Keystone virus, a California-serogroup orthobunyavirus, was first isolated in 1964 from mosquitoes in Keystone, Florida. There were no prior reports of isolation from humans, despite studies suggesting that ~20% of persons living in the region are seropositive. We report virus isolation from a Florida teenager with a rash and fever.