BOSTON (WWLP) – Eastern equine encephalomyelitis virus has been detected in Massachusetts mosquitoes for the first time this year, prompting state health officials to urge residents to take precautions against mosquito bites.
West Nile virus detected in mosquitoes in Pittsfield
The Massachusetts Department of Public Health said Wednesday that EEE was found in mosquito samples collected Aug. 17 in Kingston, in Plymouth County. No human or animal cases of EEE have been reported in Massachusetts so far this year.
The finding raises the EEE risk level to moderate in Carver, Halifax, Kingston, and Plympton.
“The last EEE outbreak in Massachusetts occurred in 2024 and, since then, there have been no human cases of EEE reported in the state,” said Public Health Commissioner Robbie Goldstein, MD, PhD.
The Department of Public Health recommends that people use mosquito repellent when spending time outdoors to enjoy the rest of the summer and reduce their risk of being bitten.
“Today’s finding alerts us to the presence of EEE in Massachusetts this year. While this is late in the season for the first detection of EEE in mosquitoes, given the evidence of West Nile virus in mosquitoes in Massachusetts, we are asking everyone in Massachusetts to take the necessary precautions to prevent mosquito bites,” added Commissioner Goldstein.
EEE is a rare but serious disease that can affect people of all ages and can be fatal. The virus is generally spread to people through the bite of an infected mosquito.
Massachusetts recorded 12 human EEE cases and six deaths in 2019, followed by five cases and one death in 2020. In 2024, the state reported four human cases and one death. No human cases were reported in 2021, 2022, 2023 or 2025.
“EEE activity in Massachusetts tends to occur in outbreak cycles,” said State Epidemiologist Dr. Catherine M. Brown. “When EEE is found in mosquitoes later in the season like this, there is less opportunity for the risk to increase to very high levels. But anytime EEE virus is in mosquitoes, it can be spread to people. We rely on our mosquito surveillance program to monitor for the presence of the virus to let people know when and where the risk is occurring so they can take steps to protect themselves.”
How to protect against mosquito bites
State health officials recommend using an EPA-registered mosquito repellent containing DEET, permethrin, picaridin, oil of lemon eucalyptus or IR3535 when spending time outdoors.
Residents are also encouraged to wear long sleeves, long pants and socks, particularly when mosquito activity is elevated. Dusk to dawn are peak biting hours for many mosquitoes, and people in higher-risk areas are encouraged to consider rescheduling outdoor activities during those times.
People can also reduce mosquito breeding areas around their homes by draining standing water from items such as flowerpots and wading pools, checking gutters and drains and frequently changing water in birdbaths.
Officials recommend keeping window and door screens tightly fitted to prevent mosquitoes from entering homes.
Animal owners urged to take precautions
State officials are also encouraging animal owners to eliminate standing water from buckets, tires, wading pools, and other containers.
Water troughs should be flushed at least once a week during the summer to reduce mosquito breeding near paddock areas. Horse owners are encouraged to keep horses indoors at night and speak with their veterinarians about mosquito repellents and vaccinations approved for animals.
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