Second batch of human-biting mosquitoes infected with eastern equine encephalitis found on North Shore

Human-biting mosquitoes infected with eastern equine encephalitis have been detected in Lynnfield—the second time this month that insects capable of spreading the sometimes-fatal disease to people have been found in Northeastern Massachusetts.

A similar batch was found earlier this month in Reading, next door to Lynnfield.

Disease trackers said Monday they also pinpointed the virus—commonly known by the acronym EEE—on the North Shore in mosquito samples collected recently in Hamilton and Haverhill, but said those insects are typically the type that bite birds, not people.

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“We don’t see generally a ton of EEE activity in Northeastern Massachusetts, so any activity makes us pay attention,” said Catherine Brown, state public health veterinarian.

Brown also said eastern equine testing is being performed on samples taken from a recently euthanized North Shore horse suspected of being sickened by the virus. She declined to identify where the horse was stabled.

A man in his 60s from the Metrowest region of Middlesex County who was treated for the virus late last month is the only Massachusetts resident to be diagnosed this season, but public health officials have said he apparently was infected during out-of-state travels.

This has been a hectic summer for public health officials, with eastern equine-bearing mosquitoes found weeks earlier than normal following an unusually warm winter. Planes have twice sprayed pesticide to kill disease-carrying mosquitoes across communities in Southeastern Massachusetts, typically a hotbed for eastern equine because of the Hockomock Swamp, a prime breeding ground for the insects.

Several towns along the North Shore have recently conducted ground spraying from trucks, and the city of Haverhill planned to spray Monday night, in response to the latest EEE finding.

Disease trackers have also found considerable evidence of West Nile virus this season, another mosquito-borne disease that is not considered as serious as eastern equine. As many as one-third of patients with symptoms of eastern equine die,

“EEE scares people more and they pay more attention, but from a public health standpoint, we know there are infected mosquitoes out there and they could be carrying EEE and West Nile,” Brown said.

She urged residents to take precautions to avoid mosquito bites, including using insect repellent, covering exposed skin when outside, and avoiding outdoor activities between dusk and dawn, when mosquitoes are most active.

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