BOSTON (WHDH) - A woman who was being treated for Eastern Equine Encephalitis at Tufts Medical Center in Boston has died.

59-yea-old Laurie Sylvia was the fourth person in Massachusetts to contract EEE this year, according to the Department of Public Health. Health officials said 38 communities have been found to be at high or critical risk for EEE, with Methuen as the latest town at critical risk after a horse tested positive for the disease.

Sylvia’s co-worker at Pelliteir Realty in New Bedford said she fell ill two weeks ago, was officially diagnosed with the mosquito-borne virus Friday and died two days later on Sunday.

“It’s a really serious disease,” said Dr. Catherine Brown of the state Department Of Health. “We see a mortality rate of approximately 40 percent and 80 percent of survivors have some level of the neurological impairment.”

Health officials say EEE usually comes about three to 10 days after someone is bit by a mosquito. It’s not clear when that happened to Sylvia.

“The disease starts with a fever, headache, chills really not feeling well but because this is a virus that invades the central nervous system,” Brown said. “You’ll see a rapid progression to loss of consciousness, seizures, come and perhaps even fatality.”

On most days, Sylvia’s colleagues say she worked selling homes in Southeastern Massachusetts or was with her family in Fairhaven. She was married for 40 years, a mother of three and a grandmother of 6.

Her daughter Jen posted a tribute to her on Facebook.

“I had to say goodbye to my best friend,” Jen posted. “My mum was my favorite person in the world.  She brought light and joy to everyone she came across … I just don’t understand how such a beautiful person could be taken from me so soon.”

This year is the first since 2013 that people in Massachusetts have been diagnosed with EEE. Health officials say they’ve found the virus in 334 mosquito samples this year, and many of the bugs are capable of spreading the virus to humans. Several communities — including Sylvia’s town of Fairhaven — are doing aerial spraying. They’re also restricting outdoor activity from dusk til dawn when mosquitoes are most active.

Brown said people need to take caution, but not be overly fearful.

“We need to put this in prospective,” Brown said. “Yes it’s a very bad disease when you get it, but the fact is that it remains rare.”

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