Mosquito surveillance and polymerase chain reaction detection of West Nilevirus, New York State

West Nile (WN) virus was detected in the metropolitan New York City (NYC) a rea during the summer and fall of 1999. Sixty-two human cases, 7 fatal, wer e documented. The New York State Department of Health initiated a departmen tal effort to implement a statewide mosquito and virus surveillance system. During the 2000 arbovirus surveillance season, we collected 317,676 mosqui toes, submitted 9,952 pools for virus testing, and detected 363 WN virus-po sitive pools by polymerase chain reaction (PCR). Eight species of mosquitoe s were found infected. Our mosquito surveillance system complemented other surveillance systems in the state to identify relative risk for human expos ure to WN virus. PCR WN virus-positive mosquitoes were detected in NYC and six counties in the lower Hudson River Valley and metropolitan NYC area. Co llective surveillance activities suggest that WN virus can disperse through out the state and may impact local health jurisdictions in the state in fut ure years.