Third resident of Massachusetts dies from rare mosquito-borne brain infection; outbreak is mainly in Northeast

A third person from Massachusetts has died from a brain infection called Eastern equine encephalitis; seven other people have also been confirmed as infected in the state.

"EEE is a rare but potentially fatal disease that can cause brain inflammation and is transmitted to humans bitten by infected mosquitoes, according to federal authorities," Danny McDonald and Abigail Feldman report for The Boston Globe. "Those who recover ... often live with severe and devastating neurological complications. There is no treatment."

Incidence of EEE from 2009 to 2018 (CDC map; click on it to enlarge)

This year's outbreak of EEE is mainly in the Northeast and is the biggest since the 1950s, with more than 30 Massachusetts towns at the highest level of risk. It's not limited to Massachusetts: at least three people in Rhode Island have been diagnosed with EEE this year, and one died this month, McDonald and Feldman report.

EEE is generally rare because the primary transmission cycle happens in and around freshwater hardwood swamps, especially in the Atlantic, Gulf Coast, and Great Lakes regions, according to the Centers for Disease Control and Prevention. An average of seven human cases are reported annually, usually from Florida, Massachusetts, New York and North Carolina.