EEE Arrives In MA: First Positive Mosquito Sample In 2023

WORCESTER, MA — After a two-year absence, the deadly Eastern equine encephalitis (EEE) virus has returned to Massachusetts.

The state Department of Public Health late last week confirmed a positive EEE sample in mosquitoes found in southern Worcester County in Douglas and Southbridge. No positive samples were found in either 2021 or 2022.

EEE hit a recent peak in 2019 when 12 humans contracted the virus resulting in six deaths. Five people contracted EEE in 2020 and one died. Those outbreaks, however, began much earlier in summer, leaving more chances for mosquitoes to spread EEE in warm weather.

"This is a late season emergence for EEE which should keep the risk level from rising too much or too quickly. However, some risk from mosquito-borne disease will continue until the first hard frost and people should take steps to prevent mosquito bites," state Public Health Commissioner Dr. Robert Goldstein said in a news release.

The risk level for EEE has moved from low to moderate in Douglas, Dudley, Southbridge, Sturbridge, Uxbridge and Webster, DPH said. The risk remains low for all other parts of the state barring any new positive samples. The chance of contracting EEE is "remote" in the Boston area and in western parts of the state, according to DPH risk maps.

EEE causes severe swelling of the brain, leading to death in about half of all cases, and disability in some who survive the disease. About 110 EEE cases have been confirmed in Massachusetts since the 1930s.

Massachusetts last week confirmed the first two human cases of West Nile virus so far this summer. To guard against both viruses, state health officials are advising residents to take safety measures like using bug spray containing DEET, treating clothes with permethrin, avoiding peak mosquito hours around dawn and dusk and wearing pants and long sleeves. Homeowners should also drain standing water to prevent mosquitoes from breeding.

Mosquito season typically ends with the first hard frost of the season, which could happen as early as October.