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West Nile Virus

The Cambridge Public Health Department leads the city's response to the risks posed by West Nile Virus, eastern equine encephalitis, and other mosquito-borne diseases.

While mosquitoes are dying off in October, the remaining mosquito population is more likely to carry West Nile virus.

Human Infections:

Six human cases of West Nile virus have been reported in Massachusetts in 2013. State health officials announced that WNV had been diagnosed in a:

  • Norfolk County man in his 30s (late August)
  • Plymouth County man in his 70s (late August)
  • Suffolk County woman in her 60s (Sept. 13)
  • Essex County man in his 60s (Sept. 23)
  • Middlesex County woman in her 50s (Sept. 27)
  • Essex County woman in her 70s (Sept. 27)

Other Updates:

  • On September 19 and August 8, state health officials announced that mosquitoes in Cambridge had tested positive for West Nile virus. 
  • As of October 2, WNV-infected mosquitos had detected in the following Greater Boston communities: Belmont, Boston, Brookline, Burlington, Cambridge, Concord, Everett, Lexington, Lincoln, Malden, Medford, Melrose, Newton, Quincy, Reading, Wakefield, Waltham, Watertown, and Wellesley. 

What is the current risk?

As of October 2, 2013, there was a moderate risk of West Nile virus in Cambridge and surrounding communities. To learn more about risk of West Nile virus in Cambridge and other Massachusetts communities see the risk map from the Massachusetts Department of Public Health.


With cooler overnight temperatures in September, mosquito activity will be concentrated during the dusk and early evening hours. It is critical for residents—especially people who are over 50 or have a weak immune system—to take precautions against mosquito bites when outdoors in the evening.

Avoid Mosquito Bites

  • Apply Insect Repellent when Outdoors. Use a repellent with DEET (N, N-diethyl-m-toluamide), permethrin, picaridin (KBR 3023), oil of lemon eucalyptus [p-methane 3, 8-diol (PMD)] or IR3535 according to the instructions on the product label. DEET products should not be used on infants under two months of age and should be used in concentrations of 30% or less on older children. Oil of lemon eucalyptus should not be used on children under three years of age.
  • Be Aware of Peak Mosquito Hours. The hours from dusk to dawn are peak biting times for many mosquitoes. Consider rescheduling outdoor activities that occur during evening or early morning
  • Clothing Can Help Reduce Mosquito Bites. Wearing long-sleeves, long pants and socks when outdoors will help keep mosquitoes away from your skin.
  • For more information on how to protect yourself, see the Cambridge Public Health Department's Prevention Tips.

Reduce Mosquito Breeding Areas

In New England, the mosquitoes that carry West Nile virus are "container breeding" species.  These mosquitoes lay their eggs in still or stagnant water found in catch basins, roof gutters clogged with leaves, old tires, flower pots, bird baths, swimming pool covers, buckets, cans, barrels, and other places where water can be trapped. Tenants, property managers, and homeowners can greatly reduce the city's mosquito population by removing mosquito breeding areas on their property.

Remove stagnant water from your property

  • Empty or treat any items that hold water, such as flower pots, birdbaths, swimming pool covers, buckets, cans, and barrels.
  • Clean rain gutters, leaves in downspouts, and pooled water on flat roofs.
  • Remove unused tires and other items that could collect water.
  • Remove containers that may hold water in places that are hard to see, such as under bushes, porches, decks, or stairs.

When you can't get rid of stagnant water by sweeping or other methods (such as Mosquito Dunk, a product sold in hardware stores), please report the address or location of the puddle or still water source to the appropriate city department:

  • Private property: Cambridge Public Health Department, 617-665-3848
  • Public property (roads, parks): Cambridge Dept. of Public Works, 617-349-4800
  • Construction sites: Cambridge Inspectional Services, 617-349-6100

If you have questions or local concerns about West Nile virus or stagnant water, please contact the Cambridge Public Health Department’s Environmental Health Division at 617-665-3838 or contact Environmental Health staff at slipson@challiance.org.

For general information, visit the Massachusetts Department of Public Health's arbovirus website and the CDC's West Nile virus website.

Last updated on October 2, 2013


For general questions about West Nile virus and eastern equine encephalitis, please call 617-665-3838. 


Join the Cambridge WNV listserv and receive seasonal updates on West Nile virus and eastern equine encephalitis.


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Cambridge Health Alliance | City of Cambridge
Cambridge Public Health Department
119 Windsor Street, Ground Level, Cambridge, MA 02139
Tel: 617.665.3800   Fax: 617.665.3888