New York State West Nile Virus Response Moves to Next Phase

Laboratory Research to Continue; State Examines Response Strategies for Next Year

Albany, December 27, 2001 – Although the acute threat from West Nile virus has ended for the time being, State officials continue to respond to the emerging disease through laboratory research and planning for next year's West Nile virus response.

"With winter now upon us and the risk of West Nile virus diminished, Department staff are working diligently with our counterparts on the federal and local levels to put the lessons learned from our continuing West Nile virus response to work to protect New Yorkers in the future," State Health Commissioner Antonia C. Novello, M.D., M.P.H., Dr.P.H. said. "Although not all counties had evidence of West Nile virus during 2001, we cannot afford to relax our vigilance against this very serious health threat."

The State Health Department currently is designing research studies and analyzing data collected during the past spring and summer months in order to update New York's West Nile Virus Response Plan. The plan outlines a comprehensive West Nile virus response strategy incorporating disease prevention, human, animal and mosquito surveillance and vector control activities to reduce the incidence of serious human illness.

During this past year, a total of 13 New Yorkers became seriously ill with West Nile virus, two of whom died. During the initial outbreak, 62 individuals in New York State were sickened by West Nile virus and seven died. Last year, 14 New Yorkers were diagnosed with West Nile virus and one died.

The State's accomplishments in responding to West Nile virus during 2001 include co–sponsoring a world conference on West Nile virus; working with local health officials and representatives of environmental groups to devise a response strategy that minimized the need for spraying; using a computer model based on dead crow density to predict human health risk; and providing a toll–free number staffed by USDA Wildlife Services experts to make it easier for New Yorkers to report dead birds.

The 2001 West Nile virus response:

During 2001, New York State's West Nile virus response focused largely on disease prevention through public education, personal mosquito protection, and reduction of larval–stage mosquitoes through habitat management (reducing collections of stagnant water or treating them with larvacide). An extensive media campaign urged New Yorkers to "Fight the Bite" through television and radio advertisements, outdoor media, novelty items and publications. The State Health Department's world conference on West Nile virus, sponsored in collaboration with the Centers for Disease Control and Prevention, the New York City Department of Health and Mental Hyigene and the New York Academy of Science, drew participants from across the United States and seven nations from Europe, Africa, Asia and Australia.

Laboratory testing continued to be important during 2001. As part of the surveillance effort, scientists at the State Health Department's Wadsworth Center laboratories tested tissue specimens from more than 3,600 dead birds for West Nile virus. Of these birds and additional birds tested by other laboratories, a total of 705 dead birds and 71 live birds have tested positive to date for West Nile virus. West Nile virus also has been identified in 300 mosquito pools submitted for testing, and in 22 horses.

As in 2000, the New York City boroughs and four nearby counties (Nassau, Suffolk, Rockland and Westchester) experienced a moderate risk of West Nile virus based on dead crow densities, whereas dead crow densities were lower in upstate counties. In all, 22 New York State counties had laboratory–confirmed findings of West Nile virus during 2001. Nassau County experienced the highest dead crow density; Suffolk County had the most infected dead birds (241); while New York City confirmed the presence of the virus in the majority of mosquito pools.

In order to investigate potential human cases of West Nile virus, Wadsworth Center scientists tested blood and/or cerebrospinal fluid from more than 500 individuals. During 2001 human cases of West Nile virus occurred in New York City, Nassau County and Suffolk County. One other case occurred in a laboratory worker who is not affiliated with the State Health Department.

WNV research:

In addition to devising a comprehensive response to minimize the human health impact from West Nile virus, the State Health Department has conducted important research to help scientists better understand the disease. Much of this research––describing epidemiologic characteristics (e.g., case numbers, patient risk factors, geographic distribution of cases) of the 1999 and 2000 outbreaks, genetically analyzing the strains of West Nile virus found in New York isolates, and showing the usefulness of measures such as dead crow density––was published in the July/August 2001 issue of Emerging Infectious Diseases. A manuscript describing the distribution of Ochelrotatus japonicus, a recently–introduced mosquito species implicated in West Nile virus transmission, has been submitted for publication.

Several other research projects either started or progressed in 2001, including studies to determine the role ticks play in the transmission cycle of West Nile virus. Another study is analyzing the blood meals of recently–fed mosquitoes to try to discern feeding preferences of various species of mosquitoes found in New York State. Building on its earlier findings that dead crow density can be used to help gauge human health risk on a county level, the Department currently is studying whether a similar approach can be employed on a smaller geographic scale. Another research project, in partnership with Oxford University and researchers at NASA's Goddard Space Center, will determine whether data gathered from satellites, in conjunction with epidemiologic surveillance data, can be used to create West Nile virus risk maps.

Next steps:

The Department will review its own and published research findings, design additional research studies and analyze surveillance data collected during 2001 to determine what, if any, changes should be made to further enhance the State's West Nile virus response. Once 2001 data are reviewed and finalized, the plan will be revised in cooperation with agency, university and environmental group partners, as appropriate.

Dr. Novello said, "We believe it is vital that our State continues to mount the most effective and appropriate response to West Nile virus. This health threat affects individuals throughout New York State, and New Yorkers will continue to feel a profound impact from this little understood and potentially lethal disease. No matter what changes are made in the State's response plan, it is certain that public education and prevention strategies must remain our first line of defense."

Specific data about West Nile virus in New York State are available from the State Health Department web site ( The site also contains links to other West Nile virus–related information.

12/27/01–137 OPA