EEE risk levels remain elevated in multiple communities

The Massachusetts Department of Public Health (DPH) today announced a fourth human case of Eastern equine encephalitis (EEE) in the state this year. The case is a man in his 50s with exposure in an area in Middlesex County at high risk for EEE.

“This year’s EEE season has been particularly active and is generating a lot of concern in communities across Massachusetts,” said Public Health Commissioner Robbie Goldstein, MD, PhD. “While EEE remains a rare disease, the risk level is elevated in multiple communities. With the weather forecast showing warm, sunny weather for the rest of the week, we recommend that people take necessary precautions in areas of elevated risk. This includes recommending that residents and towns in areas at high risk for EEE reschedule their evening outdoor events to avoid peak mosquito biting hours from dusk to dawn.”

There have been 91 EEE-positive mosquito samples in Massachusetts this year. While most activity has been focused in Plymouth and Worcester counties, infected mosquitoes have also been found in Bristol, Essex, and Middlesex counties. There are no additional risk level changes associated with today’s announcement.

EEE is transmitted to humans through the bite of an infected mosquito. The last outbreak of EEE in Massachusetts occurred in 2019-2020 and resulted in 17 human cases with seven deaths. In addition to this year’s four human cases, EEE has also been identified in two horses in Massachusetts.

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, such as DEET (N,N-diethyl-m-toluamide), permethrin, picaridin (KBR 3023), or 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 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 West Nile virus (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.

– Massachusetts Department of Public Health (DPH)