In the summer and fall of 2019, Massachusetts experienced one of the worst EEE outbreaks in US history. Twelve people in the state were infected with Eastern Equine Encephalitis — a rare but devastating neurological disease with a mortality rate of approximately 33%. The Massachusetts Department of Public Health ordered aerial spraying across dozens of towns in 13 counties and issued orders closing parks and canceling outdoor events after dark across a significant portion of the state.
The 2019 outbreak served as a stark reminder that mosquito-borne disease in Massachusetts is not a theoretical concern — it's a documented public health emergency that can emerge with little warning in any summer with the right conditions.
What Is EEE?
Eastern Equine Encephalitis is a viral disease transmitted to humans by infected mosquitoes — primarily the freshwater swamp mosquito Culiseta melanura, which cycles the virus between mosquitoes and birds, and bridge vector species like Aedes sollicitans and Coquillettidia perturbans that transmit to humans and horses.
EEE is rare (Massachusetts typically sees 0–4 human cases per year in most years) but severe. Approximately one-third of human cases are fatal; survivors often experience lasting neurological damage. There is no treatment for EEE — supportive care only. Prevention is the only protection.
High-risk areas: EEE risk is highest in low-lying areas near freshwater swamps, wetlands, and standing water — particularly in Plymouth, Bristol, Norfolk, and Worcester counties. The risk map changes year to year based on virus activity in sentinel chickens and mosquito pools tested by the MA DPH.
West Nile Virus in Massachusetts
While EEE gets more attention for its severity, West Nile Virus (WNV) is actually more commonly detected in Massachusetts each year — with human cases documented statewide. WNV is transmitted primarily by Culex pipiens and related species that breed in standing water and are active through late summer and early fall.
MA Mosquito Season and Timing
- May–June: Mosquito populations build; low disease risk early in season
- July–August: Peak mosquito activity; WNV risk present; EEE risk begins if conditions are favorable
- September–October: EEE risk is highest in late summer / early fall; many EEE cases in MA have occurred in September
- November: Frost typically ends mosquito season in most of MA
Professional Mosquito Control for MA Homeowners
Licensed MA pest control applicators (MA DPH/DAR pesticide licensing) offer residential mosquito management programs that complement the public mosquito control districts:
- Barrier spraying: Application of pyrethroid insecticides to vegetation, shrubs, and lawn edges where mosquitoes rest. Most barrier spray programs run May–September on a 3-week cycle.
- Standing water treatment: Application of BTi (Bacillus thuringiensis israelensis) — a biological larvicide — to standing water on your property. Birdbaths, clogged gutters, tarps, pot saucers, and yard debris are primary breeding sources.
- Misting systems: Automated misting systems installed on the property perimeter can provide continuous barrier treatment — popular in MA properties near wetlands with intense mosquito pressure.
Does Massachusetts have public mosquito control?
Yes — most MA municipalities belong to mosquito control districts that conduct surveillance, larval control, and aerial and ground adult spraying when risk thresholds are exceeded. However, public programs focus on public spaces and high-risk areas. Residential backyard mosquito pressure is largely a private responsibility.
Ready to Get Free Quotes?
HomeRateMap connects you with licensed local contractors in minutes — no obligation, no pressure.
Get Free Quotes →