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Mosquito-borne illness

This fact sheet answers frequently asked questions about mosquito-borne illness in Boston.

Mosquitoes in Boston can spread West Nile Virus (WNV) and Eastern Equine Encephalitis (EEE). People can get WNV or EEE when an infected mosquito bites them. Mosquitoes get these diseases by biting infected birds. People cannot get WNV or EEE from birds. Most people bitten by infected mosquitoes experience no symptoms or mild symptoms. Some can develop serious disease.

The basics

Do people in Boston get sick from mosquitoes?

We can find WNV in Boston mosquitoes every year since 2000 and has caused some people to get very sick. EEE occasionally shows up in Boston mosquitoes. Cases of EEE in people are extremely rare in Boston, but can happen.

Am I at risk?

Mosquitoes in Boston are most active and most likely to carry disease from July to September. However, they can spread disease until the first hard frost. People over age 50 are most at risk of experiencing serious illness if infected with WNV. EEE can cause serious illness in any age group.


What should I do if a mosquito bites me?

Both WNV and EEE are rare, and it is unlikely that you will get sick from a mosquito bite. However, you should contact your health care provider immediately if you develop:

  • high fever
  • confusion
  • severe headache
  • stiff neck
  • if your eyes become sensitive to light


How can I help prevent mosquito-borne illnesses?

If you are outdoors from dusk to dawn, or in an area with mosquitoes, consider these options to stop mosquito bites:

  • Use mosquito repellent
  • Use repellents containing DEET, oil of lemon eucalyptus, Picaridin or IR3535
  • Always read the directions on the label
  • Apply DEET to exposed skin (avoid eyes and mouth) and on clothes, but not on open cuts or wounds
  • Do not apply underneath clothes
  • After returning indoors, wash off repellent with soap and water. If you applied the product directly to clothing, wash it before wearing again
  • Use only approved repellents on pets
  • Do not use DEET concentrations of more than 30%
  • Do not let children apply repellents to themselves
  • Do not apply repellents to children’s eyes, mouth, or hands and use cautiously around ears
  • Do not apply DEET to infants or oil of lemon eucalyptus on children under 3 years of age. Use mosquito netting as an alternative

Cover up

  • Wear protective clothing such as long sleeved shirts, long pants, and socks whenever possible. Tuck your shirt into your pants to keep mosquitoes from going under your clothes

Avoid mosquitoes

  • Although mosquitoes can bite at any time of day, they are most active from dusk to dawn. Try to limit the time you spend outdoors during this time.

Protect your home

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

Help stop mosquito breeding

Mosquitoes lay their eggs in standing water. Make sure items around your home do not collect water. It only takes one week for a mosquito larva living in water to grow into an adult. Be sure to drain any items holding water once a week to prevent mosquito breeding, such as:

  • Containers: Turn over or cover up unused flower pots, buckets, garbage cans, and wheelbarrows. Change water in bird baths once a week
  • 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. Keep large pools treated and circulating
  • Old tires: Cover or dispose of them. They are a favorite mosquito-breeding site
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