- Department of Public Health
Media Contact
Katheleen Conti, Assistant Director of Media Relations
Boston — The Massachusetts Department of Public Health (DPH) today announced that the risk for West Nile virus (WNV) is now high in multiple communities due to ongoing evidence of mosquito samples carrying the virus. The risk level for WNV has been elevated in the following municipalities: Acton, Bedford, Billerica, Boston, Brookline, Carlisle, Chelmsford, Dracut, Lowell, and Newton.
The State Public Health Laboratory confirmed the first WNV-positive mosquitoes in Massachusetts this year on June 17. Since then, there have been 168 WNV-positive mosquito samples detected from Barnstable, Berkshire, Bristol, Dukes, Essex, Franklin, Hampden, Middlesex, Norfolk, Plymouth, Suffolk, and Worcester counties. There has also been one animal case of WNV confirmed this year in a goat in Lunenburg. No human cases of WNV have been confirmed in Massachusetts so far this year.
In addition to WNV, Eastern equine encephalitis (EEE) has also been detected in mosquitoes in Massachusetts this year. Belchertown, Granby, Pelham, and Ware in Hampshire County are currently at moderate risk for EEE. The following 12 municipalities in Bristol and Plymouth counties, a historic area of EEE activity, are also currently at moderate risk: Bridgewater, Carver, East Bridgewater, Easton, Halifax, Hanson, Lakeville, Middleborough, Plympton, Raynham, Taunton, and West Bridgewater.
There have been seven EEE-positive mosquito samples detected and no confirmed human or animal cases so far this year.
“Both West Nile virus and EEE pose risk to the people in Massachusetts,” said Public Health Commissioner Robbie Goldstein, MD, PhD. “The weather remains warm and somewhat humid, which increases mosquito activity. I encourage everyone to take measures to protect themselves: use mosquito repellent when outdoors, wear long sleeves and pants, and be aware of peak mosquito hours.”
WNV and EEE are generally transmitted to humans through the bite of an infected mosquito. There were 19 human cases of WNV in Massachusetts reported in 2024 and no animal cases. There were four human cases of EEE in Massachusetts last year with one death and three animal cases.
“WNV findings in mosquitoes have accelerated rapidly over the last several weeks,” said State Epidemiologist Catherine M. Brown, DVM, MSc, MPH. “We are now in the peak time for transmission of mosquito-borne disease to people and it is important for people to know that so they can take steps to protect themselves.”
People have an important role to play in protecting themselves and their loved ones from illnesses caused by mosquitoes.
Avoid Mosquito Bites
Apply Insect Repellent when Outdoors. Use a repellent with an EPA-registered ingredient, such as DEET (N,N-diethyl-m-toluamide), permethrin, picaridin (KBR 3023), or oil of lemon eucalyptus (p-menthane-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 percent 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 in areas of high risk.
Clothing Can Help Reduce Mosquito Bites. Wearing long sleeves, long pants and socks when outdoors will help keep mosquitoes away from your skin.
Mosquito-Proof Your Home
Drain Standing Water. Mosquitoes lay their eggs in standing water. Limit the number of places around your home for mosquitoes to breed by draining or discarding items that hold water. Check rain gutters and drains. Empty unused flowerpots and wading pools and change the water in birdbaths frequently.
Install or Repair Screens. Keep mosquitoes outside by having tightly fitting screens on all windows and doors.
Protect Your Animals
Animal owners should reduce potential mosquito breeding sites on their property by eliminating standing water from containers such as buckets, tires, and wading pools – especially after heavy rains. Water troughs provide excellent mosquito breeding habitats and should be flushed out to reduce mosquitoes near paddock areas. Horse owners should keep horses in indoor stalls at night to reduce their risk of exposure to mosquitoes. Owners should also speak with their veterinarian about mosquito repellents approved for use in animals and vaccinations to prevent West Nile virus (WNV) and EEE. If an animal is suspected of having WNV or EEE, owners are required to report to the Department of Agricultural Resources, Division of Animal Health by calling 617-626-1795, and to the Department of Public Health by calling 617-983-6800.
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