Updates By Carol A. Kemper, MD, FACP

Did West Nile Virus Survive the New York Winter?

Sources: Cooper J, et al. MMWR Morb Mortal Wkly Rep 2000:49:178-179; ProMED-mail. March 14 and 22, 2000. www.pro-medmail.org.

Mosquitoes that have survived the winter in New York in underground structures have been found to harbor bits of West Nile virus (WNV) RNA. A total of 67 pools of water containing dormant Culex spp. mosquitoes were analyzed, three of which yielded portions of envelope RNA, although the virus itself could not be isolated. It is hoped this may represent noninfectious viral particles, but there is concern that low titers of viable virus could escape detection. In another report, a redtail hawk that died in Connecticut two months ago had evidence of WNV infection, suggesting that low-level infection in the bird population may be occurring despite the cold weather.

These findings suggest that additional cases are likely with warmer weather. Plans are being stepped up in several states this spring to monitor potential hosts for infection along the Atlantic and Gulf coasts. Seropositive birds were found last summer in New Jersey, New York, and Maryland.

In the meantime, New Yorkers are being advised to wear long sleeves and plenty of insecticide should they venture outdoors, and to avoid areas of standing water. At least 69 New Yorkers became ill with WNV infection last year—seven of whom died. Recent data extrapolated from a serosurvey of residents in northern Queens, which is considered the epicenter of last year’s outbreak, suggest that somewhere between 533 and 1903 people may have been infected with WNV last summer, representing ~2.6% of the residents in Queens.