California Serogroup Viruses

(California encephalitis, La Crosse encephalitis, Jamestown Canyon)

Fight the Bite SloganCalifornia serogroup viruses including California encephalitis, Keystone, La Crosse, Jamestown Canyon, snowshoe hare, and trivittatus are all mosquito-borne arboviral infections. In the United States, La Crosse virus (LACV) is the most common of the California serogroup viruses. Both LACV and Jamestown Canyon virus (JCV) infections have been reported in Wisconsin. People infected with California serogroup viruses may have no apparent symptoms. Some people have symptoms of illness that may range from mild fever to encephalitis or mengioencephelitis.

La Crosse encephalitis disease mostly occurs in the Midwestern, mid-Atlantic, and southeastern states of the United States. LACV was first identified in 1960 in a Minnesota resident who was diagnosed in La Crosse, Wisconsin. From 2002 to 2008, 68 cases of La Crosse encephalitis (average 10 cases/year) were reported in Wisconsin. Initial symptoms of illness may include fever, headache, nausea, vomiting, and tiredness. Some people may develop severe neuroinvasive disease (disease that affects the nervous system). Severe symptoms often involve encephalitis (an inflammation of the brain) and can include seizures, coma, and paralysis. Historically, most of the LACV infections in Wisconsin have been reported in children less than 16 years old; however, recent surveillance data show that both adults and children can become ill with La Crosse encephalitis.

Jamestown Canyon virus was first recognized as causing human illness in 1980 and occurs throughout temperate climate regions of North America. JCV infections have been rarely reported in Wisconsin, but because of the unavailability of a commercial test to detect the virus, the infection may be unrecognized and under reported.

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Last Revised: June 5, 2018