West Nile Virus Infection in Birds and Mosquitoes
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 birds and 9,954 mosquito pools for WN virus during the transmission season. Sixty-three avian species, representing 30 families and 14 orders, tested positive for WN virus. The highest proportion of dead birds that tested positive for WN virus was in American Crows in the epicenter (67% positive, n=907). Eight mosquito species, representing four genera, were positive for WN virus. The minimum infection rate per 1,000 mosquitoes (MIR) was highest for 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 American Crows that tested positive for WN virus (92%, n=48) and the highest number of human cases (n=10).
The emergence of West Nile (WN) virus in 1999 in four U.S. states was followed by its spread to 12 states in 2000. An enzootic cycle was established between birds and mosquitoes, and WN disease was observed in humans, horses, and birds in both years. Bird deaths due to WN virus are unusual outside North America, with the exception of deaths of geese in Israel and pigeons in Egypt. In 1999 in North America, WN disease, characterized by meningoencephalitis and myocarditis, was observed in 14 species of wild and captive birds. WN virus has been detected in a number of mosquito genera in North America, including Culex and Aedes species. Vector competence has been confirmed experimentally for some North American species, including Cx. pipiens, Ae. vexans, and Ae. japonicus.
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 birds and 9,954 mosquito pools for WN virus during the transmission season. Sixty-three avian species, representing 30 families and 14 orders, tested positive for WN virus. The highest proportion of dead birds that tested positive for WN virus was in American Crows in the epicenter (67% positive, n=907). Eight mosquito species, representing four genera, were positive for WN virus. The minimum infection rate per 1,000 mosquitoes (MIR) was highest for 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 American Crows that tested positive for WN virus (92%, n=48) and the highest number of human cases (n=10).
The emergence of West Nile (WN) virus in 1999 in four U.S. states was followed by its spread to 12 states in 2000. An enzootic cycle was established between birds and mosquitoes, and WN disease was observed in humans, horses, and birds in both years. Bird deaths due to WN virus are unusual outside North America, with the exception of deaths of geese in Israel and pigeons in Egypt. In 1999 in North America, WN disease, characterized by meningoencephalitis and myocarditis, was observed in 14 species of wild and captive birds. WN virus has been detected in a number of mosquito genera in North America, including Culex and Aedes species. Vector competence has been confirmed experimentally for some North American species, including Cx. pipiens, Ae. vexans, and Ae. japonicus.
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