A case of encephalitis in a human associated with a serologic rise to Jamestown Canyon virus.

An 8-year-old girl living in rural southwestern Michigan experienced sudden onset of symptoms beginning with headache, dizziness and fever which rapidly progressed to central nervous system involvement with seizures and coma. Following 27 days of hospitalization her recovery was uneventful, with no apparent sequelae 15 months after discharge. Serologic studies of paired sera showed a rise in antibody to Jamestown Canyon virus, a member of the California serogroup (family Bunyaviridae). Specific IgM anti-Jamestown Canyon virus antibody was detected in sera drawn 9 days after onset. A concomitant rise in complement fixation antibody to herpesvirus was also noted. We believe this is the first reported case of encephalitis associated with Jamestown Canyon virus infection. Reasons are presented for the current inability to routinely detect infection and clinical illness caused by this virus.