If you work outdoors, West Nile virus may be of concern to you, since it can be spread by bites from infected mosquitoes. It’s important to note that most people infected with West Nile virus will not get sick. However, some people after being bitten may become ill in three-to-15 days. They develop a mild illness with fever, headache, body aches, and sometimes skin rash and swollen glands. At this time, there are no known long-term effects due to this mild illness.

On rare occasions, a West Nile virus infection will result in a severe illness known as West Nile encephalitis (encephalitis is an inflammation of the brain). In a small number of cases, this more serious disease can be fatal.

Spread of the virus

West Nile virus is typically spread by birds and mosquitoes. A mosquito becomes infected when it feeds on a bird carrying the virus. The infected mosquito can then transmit the virus when it bites another bird, person, or other animal. At this time, transmission of the virus from person to person is only thought to be possible during blood transfusions, organ transplants, or through breast milk.

West Nile virus was first recognized in New York City in 1999. It is not known how the virus was introduced into the United States, but it has spread from New York to almost every state in the U.S., and it continues to spread. The virus has been found in humans, horses, many types of birds, and some other animals.

Risk of exposure

You are at highest risk of exposure to the virus if you work outdoors when mosquitoes are actively biting. Dawn and dusk are the most likely times to be bitten by a mosquito. In northern states, this is during the summer months, but in southern states, mosquitoes are active year-round. Persons 50 years of age or older have a greater risk of contracting the more serious illness, West Nile encephalitis.

Protecting yourself

You can protect yourself from becoming infected in a number of ways. If you work outdoors, you can use these personal protective measures to reduce contact with mosquitoes:

  • Wear long-sleeved shirts, long pants, and socks when possible.
  • Spray exposed skin with insect repellant.
    • Read and follow label directions for repellant use.
    • Use DEET (N-N-diethyl-3-methylbenzamide) at concentrations of 35 percent or less.
    • Do not apply repellants to cuts, wounds, or irritated skin.
    • When needed, reapply repellants according to label directions.
  • Spray clothing with repellant, as mosquitoes may bite through thin clothing.
  • Do not apply repellants under clothing.
  • Wash treated clothing before wearing it again.

You can also protect yourself by not letting mosquitoes breed in your area. Eliminate as many sources of standing water as possible, because mosquitoes lay their eggs in standing water. Turn over, cover, or remove equipment such as tarps, buckets, barrels and wheelbarrows that may accumulate water. Place drain holes in containers that cannot be discarded. Routinely empty water from containers that collect water in which mosquitoes can lay their eggs.

More information

For more detailed information and updates with new information, visit the Centers for Disease Control’s West Nile Virus page.

If you have any health concerns or questions, contact your health care provider.

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The above evaluations and/or recommendations are for general guidance only and should not be relied upon for medical advice or legal compliance purposes. They are based solely on the information provided to us and relate only to those conditions specifically discussed. We do not make any warranty, expressed or implied, that your workplace is safe or healthful or that it complies with all laws, regulations or standards.

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