West Nile virus infection in birds and mosquitoes, New York State, 2000

West Nile (WN) virus was found throughout New York State in 2000, with the epicenter in New York City and surrounding counties. We tested 3,403 dead b irds and 9,954 mosquito pools for WN virus during the transmission season. Sixty-three avian species, representing 30 families and 14 orders, tested p ositive for WN virus. The highest proportion of dead birds that tested posi tive for WN virus was in American Crows in the epicenter (67% positive, n=9 07). Eight mosquito species, representing four genera, were positive for WN virus. The minimum infection rate per 1,000 mosquitoes (MIR) was highest f or Culex pipiens in the epicenter: 3.53 for the entire season and 7.49 for the peak week of August 13. Staten Island had the highest MIR (11.42 for Cx . pipiens), which was associated with the highest proportion of dead Americ an Crows that tested positive for WN virus (92%, n=48) and the highest numb er of human cases (n=10).