The man, who was not identified, is over 60 years old and lives in southern Plymouth County, according to a Saturday announcement from the Massachusetts Department of Public Health.
The human case is the first in the state since 2013. Laboratory testing confirmed the man’s diagnosis.
In a Facebook post, a woman who lives in Rochester — one of the communities that's now considered to be at a “critical” risk level for EEE — said her father was diagnosed with the virus and is now in a coma.
"Life was flipped upside down for my family this week. My dad has been in a coma since Monday night and it’s been a long week as the doctors have searched for answers," Tess Hiller Hedblom said in the Sunday post.
Hedblom, who called her father's diagnosis “shocking and heartbreaking," said it's not clear when or where he was bitten by the infected mosquito.
"Right now we are trying to get through minute by minute. We are asking our family, friends and community to continue praying and hope for a miracle," she concluded.
EEE, according to the Centers for Disease Control and Prevention (CDC), is a rare disease that’s spread by infected mosquitoes. EEEV “is one of a group of mosquito-transmitted viruses that can cause inflammation of the brain (encephalitis),” the federal health agency says.
EEE is more common in Atlantic and Gulf Coast states, though the CDC said some cases have been reported in the Great Lakes area. It’s rare -- only 5 to 10 cases are reported each year in the U.S.
Symptoms of EEE typically appear four to 10 days after a person is bitten by an infected mosquito. Severe cases of the virus “begin with the sudden onset of headache, high fever, chills and vomiting,” said the CDC, which noted, “the illness may then progress into disorientation, seizures, and coma.”
One-third of those infected with EEE virus die, while survivors typically have “mild to severe brain damage.”
There’s no specific treatment for the infection.
“Antibiotics are not effective against viruses, and no effective antiviral drugs have been discovered," the CDC said. "Severe illnesses are treated by supportive therapy, which may include hospitalization, respiratory support, IV fluids, and prevention of other infections."
The best way to prevent EEE virus and other mosquito-borne ailments is by draining standing water — like in birdbaths, buckets or on pool covers — as stagnant water can serve as a breeding ground for these insects. Other preventive measures include covering skin with long-sleeved pants and shirts while outside and properly using insect repellent containing DEET.
In Massachusetts, state officials plan to conduct aerial spraying “in specific areas of Bristol and Plymouth counties to reduce the mosquito population and public health risk,” they said.
In addition to Rochester, other areas that are considered to be at critical risk for EEE are Carver, Lakeville, Marion, Middleborough, Wareham in Plymouth County, Acushnet, Freetown and New Bedford in Bristol County, health officials said.