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Should I be Concerned about West Nile Virus and EEEV?

Provided by the Boston Public Health Commission

What is mosquito-borne illness?

Mosquito-borne illness is disease spread by the bite of an infected mosquito. In the northeastern United States, viruses such as West Nile Virus (WNV) or Eastern Equine Encephalitis virus (EEEV) have caused illness. However, the risk of becoming infected with WNV or EEEV following a mosquito bite is low. Most people bitten by infected mosquitoes experience no illness or mild illness, but a small number of people can develop disease that is more serious.

How is it spread?

Mosquito-borne illness is spread to people through the bite of an infected mosquito. Some mosquitoes can get a virus and infect certain birds. Mosquitoes can feed on infected birds. People cannot get these viruses directly from an infected bird. However, you should use gloves when handling any dead animals and put them in double plastic bags before disposing of them in the trash. Because WNV is found in the blood of an infected person, it may also be spread through blood transfusions and donated organs. It can also pass from a pregnant woman to her unborn child and through breast-feeding. However, routine exposure to a person infected with WNV does not transmit infection.

Does mosquito-borne illness occur in Boston?

WNV has been detected in Boston during the summer months every year since 2000. But human cases are extremely rare. In 2012, there were six confirmed cases of WNV in Boston. Occasionally WNV does cause serious illness or death. WNV is expected to re-appear every summer.

Am I at risk of becoming sick from mosquito bites?

The time of the year when mosquitoes are most active and most likely to carry disease is usually between July and September. However, if the weather remains warm, the risk period can extend as late as November. People at higher risk for developing serious illness from WNV infection are those over age 50. EEEV can cause severe illness in any age group.

What should I do if a mosquito bites me?

Mosquito-borne illness is very rare in Boston. Most mosquitoes don’t carry viruses that cause human illness, and the risk of illness following a mosquito bite is small. However, you should see your doctor immediately if you develop high fever, confusion, severe headache, stiff neck, or if your eyes become sensitive to light.

What should I do if I find a dead bird?

If you find a dead bird, call the State Laboratory Institute (SLI) to report it at 1-866-MASS-WNV. The SLI will determine whether or not the bird should be tested. If the bird needs to be tested, you will be asked to call the Boston Animal Control to arrange to have the bird picked up. Although not every bird will be tested, it is important for all dead birds to be reported. A large number of dead birds in a community can be a sign that mosquitoes in that area may also be carrying disease. It may also be a sign that there is an increased risk for humans to develop WNV. This will help determine the need for mosquito trapping and testing.

How can I protect myself from mosquito bites?

If you are outdoors in an area with mosquitoes, consider these options:

  • Use a mosquito repellent. The most effective repellents contain DEET, but there are several DEET alternatives that have been approved by the EPA (including oil of lemon eucalyptus tree or soybean-oil-based products). Read the directions on the product label to find out about precautions that need to be taken, how long the product offers protection and how often the product needs to be reapplied. After returning indoors, wash off repellent with soap and water.
  • If you use a product containing DEET, do not use concentrations of more than 30 percent on adults and use low concentrations of DEET on children. Apply DEET to exposed skin (not eyes or mouth) only and do not use it on open cuts or wounds. Do not let children apply DEET themselves. Do not apply DEET on infants (mosquito netting can be used over infant carriers).
  • Wear protective clothing such as a long sleeved shirt, long pants and socks.

Although mosquitoes can bite at any time of day, try to limit time outdoors between dusk and dawn when mosquitoes are most active (or use above precautions).

Make sure window and door screens don't have holes in them. Screens in good repair will help prevent mosquitoes from getting inside your house.

Mosquitoes need water to breed. They can develop into adults in a little as a week. Make sure that items like these below don't collect water, or that you clean them out once a week.

  • Containers: Turn over or cover unused flower pots, buckets, garbage cans, and wheelbarrows.
  • Gutters: Remove leaves and other debris that can clog gutters and trap water.
  • Pools: Cover unused swimming pools and turn over kiddie pools when not in use. Be sure to keep swimming pool covers clear of leaves and water.
  • Old tires: Cover or dispose of them. They are one of mosquitoes' favorite places to breed.

For more information, call the Boston Public Health Commission at (617) 534-5611.

Above content provided by the Boston Public Health Commission in partnership with Beth Israel Deaconess Medical Center. For advice about your medical care, consult your doctor.

Posted June 2013

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