EEE Surveillance Gaps Loom Across Massachusetts


BOSTON (State House News Service) — A task force created under a new law will help address gaps in surveillance of mosquito-borne illnesses, a step that the state's epidemiologist described as key as eastern equine encephalitis virus returns to the region.

EEE outbreaks tend to occur in two- to three-year cycles in Massachusetts, and after a record 2019 outbreak, Massachusetts again faces a risky year for the rare but dangerous arbovirus.

Under a bill (S 2757) Gov. Charlie Baker signed in July, officials will convene a panel -- set to launch this week -- aimed at improving statewide monitoring of how mosquito-borne viruses are transmitted and updating notifications provided about aerial spraying.

Dr. Catherine Brown, state epidemiologist and veterinarian, told the Public Health Council on Wednesday that the law will help address the fact that wide swaths of the state lack mosquito control districts, which limits the amount of data that public officials have as they work to limit the spread of the illness.

"We have these large parts of the state where there is no mosquito control district, and what is most concerning about that from a public health standpoint is it puts the burden of surveillance entirely on the state," Brown said. "We have less data from those areas than we do from places where mosquito control districts exist. This is an opportunity to really be thoughtful about what is needed in the state now that we are seeing EEE activity outside the historic hotspot of southeastern Massachusetts."

As of Wednesday, eight communities are at high or critical risk for EEE this year, all in southeastern Massachusetts: Wareham, Plympton, Kingston, Halifax, Rochester, Bridgewater, Middleborough and Carver

Baker administration communications officials were unable to provide a list of task force members Wednesday, but the legislation calls for a panel including several state officials: the energy and environmental affairs secretary, public health commissioner, commissioner of agricultural resources, commissioner of conservation and recreation, commissioner of environmental protection, and director of fisheries and wildlife -- or any of their designees -- as well as two appointees from the State Reclamation and Mosquito Control Board.

They will be tasked with recommending "comprehensive reforms of the commonwealth's mosquito control system."

EEE infections in humans are rare, but dangerous. The mortality rate is typically around 30 percent but has reached 50 percent in Massachusetts, Brown said, and among patients who recover, as many as four out of five suffer permanent neurological damage.

Last year was the most active EEE season on record since 1956, with 12 confirmed human cases and six deaths linked to the virus.

Public health officials have confirmed a single case in 2020, but Brown warned that August is typically the most active month for transmission and that the first observed case came earlier than in prior seasons -- a worrying sign about what this year could have in store.

"If you have it spread to a human earlier in the season, that is concerning because you know you have this long period of time for risk to build," she said.

However, she stressed that one season's pattern does not always reflect the next. While the cases started earlier this summer than last year, risk levels also appear to be more confined to hotspots near swampy areas, particularly in Plymouth County, than last year's widespread threat.

"If you've seen one EEE season, you've seen one EEE season," Brown said. "We learn from every single one, but there are variations in the complex ecology of EEE every year that mean we have to be thoughtful and to really pay attention to what's happening."

Compared to previous years, Massachusetts has not observed "intense" threats from West Nile virus, the other major mosquito-borne illness that afflicts the state, according to Brown.

The mosquito season arrives as the state continues to grapple with the COVID-19 pandemic, creating overlapping challenges for public health experts and simultaneous messages of caution for residents.

State-run crews performed a round of aerial spraying in southeastern Massachusetts communities facing risks starting earlier this week, and health officials also plan to increase public awareness campaigns encouraging Bay Staters to take ample precautions such as mosquito-proofing homes and wearing long sleeves.

"In the highest-risk areas, there is a recommendation to avoid outdoor activity from dusk to dawn," Brown said. "It doesn't mean avoiding outdoor activity completely. With COVID, we've been telling people we want them outside. It's merely that you should shift your outdoor activity to daylight hours when the mosquitoes most likely to carry EEE are less active."

Baker and Public Health Commissioner Monica Bharel flagged concerns last month to get the word out early, before the updated mosquito control bill became law. The new task force created by the law scheduled its first meeting for Friday.

By Chris Lisinski, State House News Service

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