Arbovirus infections in man in British Columbia.

During the summer of 1971, the first laboratory-proved cases of acute encephalitis in man due to any of the known arboviruses occurred in the south-central region of British Columbia. Five human cases of encephalitis with two deaths were diagnosed; three of these patients, including one of the fatalities, were proven in the laboratory to have contracted western equine encephalitis.During 1968 and 1969, a human serum survey undertaken in approximately 2000 life-long residents of the province discovered low levels of hemagglutinin-inhibiting and/or complement-fixing as well as neutralizing antibodies for western equine encephalitis, St. Louis encephalitis, Powassan encephalitis, California encephalitis and Colorado tick fever. Evidence of recent sub-clinical infection was detected in some cases.