Press Release  State health officials raise risk from EEE to high in six communities

Boston — The Massachusetts Department of Public Health (DPH) today announced that Eastern equine encephalitis (EEE) has been detected in additional mosquito samples collected on September 11 in Sutton and Southbridge. These findings raise the EEE risk level to high in Douglas, Dudley, Oxford, Southbridge, Sutton, and Webster, and to moderate in Auburn, Charlton, Grafton, Millbury, and Northbridge.

The first EEE-positive mosquitoes in Massachusetts in 2023 were announced on September 1 from Douglas and Southbridge. There have also been mosquitoes with EEE and a donkey with EEE infection identified in Rhode Island and EEE-positive mosquitoes in Connecticut close to the Massachusetts border. No human or animal case of EEE has been detected in Massachusetts so far this year.

“While EEE is a rare disease, it can cause severe disease resulting in hospitalization and death,” said Public Health Commissioner Robert Goldstein, MD, PhD. “We want people to take this information seriously and follow advice to prevent mosquito bites. In this case, evidence suggests that staying indoors between the hours of dusk and dawn can decrease the risk from EEE. Risk is high enough in several towns that we recommend rescheduling outdoor events.”

EEE is a rare but serious and potentially fatal disease that can affect people of all ages. EEE is generally spread to humans through the bite of an infected mosquito. There were 12 human cases of EEE in Massachusetts in 2019 with six deaths and 5 human cases with one death in 2020. There were no human cases of EEE in Massachusetts in 2021 or 2022.

“The mosquitoes that are most likely to spread EEE are most active between the hours of dusk and dawn,” said Dr. Catherine M. Brown, State Epidemiologist. “But mosquitoes also try to bite during the day, in the shade or when it is cloudy; they also thrive in humid weather. Use mosquito repellents any time you are outdoors and if you find yourself swatting mosquitoes anyway, move indoors to get away from them.”

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 (DEET (N,N-diethyl-m-toluamide), permethrin, picaridin (KBR 3023), 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 at least once a week during the summer months 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 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.

More information, including all WNV and EEE positive results, can be found on the Arbovirus Surveillance Information web page at Mosquito-borne Diseases | Mass.gov, which is updated daily, or by calling the DPH Division of Epidemiology at 617-983-6800.

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