West Nile virus surveillance in Connecticut in 2000: An intense epizootic without high risk for severe human disease

In 1999, Connecticut was one of three states in which West Nile (WN) virus actively circulated prior to its recognition. In 2000, prospective surveill ance was established, including monitoring bird deaths, testing dead crows, trapping and testing mosquitoes, testing horses and hospitalized humans wi th neurologic illness, and conducting a human seroprevalence survey. WN vir us was first detected in a dead crow found on July 5 in Fairfield County. U ltimately, 1,095 dead crows, 14 mosquito pools, 7 horses, and one mildly sy mptomatic person were documented with WN virus infection. None of 86 hospit alized persons with neurologic illness (meningitis, encephalitis, Guillain- Barre-like syndrome) and no person in the seroprevalence survey were infect ed. Spraying in response to positive surveillance findings was minimal. An intense epizootic of WN virus can occur without having an outbreak of sever e human disease in the absence of emergency adult mosquito management.