NYC Department of Health Information

What is West Nile virus?

West Nile virus is a mosquito-borne virus that can infect humans, birds, horses and other mammals. In most humans, West Nile virus infection causes a mild or moderate, short-lived flu-like illness, or causes no symptoms at all. However in some cases, particularly among persons 50 years of age and older, it can cause serious neurological diseases such as encephalitis, meningitis, or acute flaccid paralysis. West Nile virus first appeared in North America in New York City in 1999. Since then, the virus has spread across the continental United States. Visit www.cdc.gov for more information on West Nile virus nationally.

Who is most at risk for getting severe West Nile virus disease from being bitten by an infected mosquito?

Anyone who is infected can potentially develop severe West Nile virus disease (e.g. encephalitis, meningitis, or acute flaccid paralysis). However, persons older than 50 have the highest risk of becoming severely ill. There is also increasing evidence that immunocompromised persons (e.g., people who are taking immunosuppressive medications such as prednisone, or people who have received organ transplants) are at higher risk for severe West Nile virus disease.

What can I do to prevent infection with West Nile virus?

From June through October, when mosquitoes are most active, take the following precautions:

• • Wear protective clothing such as long pants and long-sleeved shirts, particularly at dusk and dawn when most mosquitoes are searching for a blood meal.
• • Avoid shaded, bushy areas where mosquitoes like to rest.
• • Limit outdoor evening activity, especially at dusk and dawn when mosquitoes are most active.
• • Use an insect repellent containing DEET, picaridin or oil of lemon eucalyptus to help reduce exposure to mosquitoes. Always read the repellents label. For more information, see DOHMH's Insect Repellent Use & Safety Fact Sheet.

There have been no reported adverse reactions following the use of repellents containing DEET in pregnant or breastfeeding women. As a precaution, prior to handling infants, nursing mothers should wash repellents off their hands and areas of the breast that an infant may contact. (Please see the DOHMH fact sheet on Insect Repellent Use & Safety).

Is the City planning to spray pesticides?

New York City may spray pesticides to target adult mosquitoes if there is a risk to human health from West Nile virus. Spraying will be concentrated in areas most at risk for disease occurrence and will be conducted by experienced and licensed applicators who are required to follow New York State Department of Environmental Conservation (NYSDEC) and EPA requirements. The City is hopeful that with an early and aggressive campaign against mosquito breeding areas, the need for the spraying of pesticides will be reduced.