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West Nile Virus Basics


Prevention: Avoid Mosquito Bites to Avoid Infection

Human illness from West Nile virus is rare, even in areas where the virus has been reported. The chance that any one person is going to become ill from a mosquito bite is low.

You can further reduce your chances of becoming ill by protecting yourself from mosquito bites. To avoid mosquito bites:

  • Apply insect repellent containing DEET (N,N-diethyl-meta-toluamide) when you're outdoors. For details on when and how to apply repellent, see Using Insect Repellent Safely from the EPA
  • When possible, wear long-sleeved clothes and long pants treated with repellents containing permethrin or DEET since mosquitoes may bite through thin clothing. Do not apply repellents containing permethrin directly to exposed skin. If you spray your clothing, there is no need to spray repellent containing DEET on the skin under your clothing.
  • Consider staying indoors at dawn, dusk, and in the early evening, which are peak mosquito biting times.
  • Limit the number of places available for mosquitos to lay their eggs by eliminating standing water sources from around your home.
  • Check to see if there is an organized mosquito control program in your area. If no program exists, work with your local government officials to establish a program. The American Mosquito Control Association can provide advice, and their book Organization for Mosquito Control is a useful reference. Another source of information about pesticides and repellents is the National Pesticide Information Center, which also operates a toll-free information line: 1-800-858-7378 (check their Web site for hours).

About the Virus, the Disease, and Its Spread

West Nile virus is spread by the bite of an infected mosquito, and can infect people, horses, many types of birds, and some other animals.

Most people who become infected with West Nile virus will have either no symptoms or only mild ones. However, on rare occasions, West Nile virus infection can result in severe and sometimes fatal illnesses.

There is no evidence to suggest that West Nile virus can be spread from person to person or from animal to person.

PLEASE NOTE:CDC is not a hospital or clinical facility; we do not see patients and are unable to diagnose your illness, provide treatment, prescribe medication, or refer you to specialists.

If you have a medical emergency, contacting CDC is not the proper way to get immediate help. If you are a patient, please see your health care provider or the nearest emergency room. If you are a health care provider, please contact your state epidemiologist or local health department.

Reporting Dead Birds

Dead birds in an area may mean that West Nile virus is circulating between the birds and the mosquitoes in that area. Over 110 species of birds are known to have been infected with West Nile virus. Although birds, particularly crows and jays, infected with WN virus can die or become ill, most infected birds do survive.

The public can play an important role in monitoring West Nile virus through reporting dead birds to state and local health departments. However, in some areas, birds are no longer being collected. Inaddition, state and local agencies have different policies for collecting and testing birds.

PLEASE NOTE: Because CDC is a federal agency, we do not deal directly with the reporting of dead birds. State and local health departments are responsible for initiating these investigations. They report their findings to CDC.

Information provided by:
CDC West Nile Virus Home Page - Division of Vector-Borne Infectious Diseases (DVBID)
For complete information and links please visit http://www.cdc.gov/ncidod/dvbid/westnile/.