Mass. officials recommend avoiding bug bites after season’s first EEE mosquito detected

The Eastern equine encephalitis virus, a rare but potentially fatal disease, has been detected in mosquitoes in Massachusetts for the first time this year, the Massachusetts Department of Public Health announced in a release Wednesday. 

The presence of EEE was confirmed in mosquito samples collected on Aug. 17 in Kingston, increasing the risk level of EEE to moderate in the communities of Carver, Halifax, Kingston, and Plympton, DPH said. 

EEE is generally spread to humans through the bite of an infected mosquito, and is a serious disease that can affect people of all ages, DPH said. No human or animal cases of EEE have been detected so far this year. 

There were no human cases of EEE in Massachusetts in 2021, 2022, 2023, or 2025. However, there were 12 human cases in Massachusetts in 2019 with six deaths, five human cases in 2020 with one death, and four human cases in 2024 with one death. 

“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 virus to let people know when and where the risk is occurring so they can take steps to protect themselves.”

Officials recommend avoiding mosquito bites by using insect repellent, with EPA-registered ingredients, when outdoors. The DPH also recommended wearing long sleeves, long pants, and socks to avoid bites. The hours from dusk to dawn are peak mosquito biting hours, DPH said.  

Mosquitos lay their eggs in standing water, so the DPH said to mosquito proof your home you should drain or discard any items that hold water. This includes checking rain gutters and drains, emptying unused flower pots and wading pools, and changing the water in birdbaths frequently. 

To protect pets, DPH recommends owners speak with their veterinarian about mosquito repellents approved for use in animals, and vaccinations to prevent EEE. DPH also recommends horse owners flush out water troughs at least once a week and keep horses in indoor stalls at night. 

“While this is late in the season for the first detection of EEE in mosquitoes, when combined with all 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,” said Public Health Commissioner Robbie Goldstein. “The Department of Public Health recommends that people use mosquito repellent when they are spending time outdoors so they can enjoy the rest of the summer and decrease their risk of being bitten.”

More information, including all EEE positive results, can be found on the Arbovirus Surveillance Information web page, or by calling the DPH Division of Epidemiology at 617-983-6800.