A man from southern Plymouth County has become the first Massachusetts resident to test positive for Eastern equine encephalitis since 2013, prompting the state to raise the risk level for the virus in nine Southeastern Massachusetts communities to critical, state officials said Saturday.
The unidentified man is over 60 and remained hospitalized Saturday, said Ann Scales, a spokeswoman for the state Department of Public Health.
Scales cautioned in an e-mail that, though the virus is rare, it “can affect people of all ages and is not more likely in people with pre-existing conditions.”
The virus can cause swelling of the brain and kills about 30 percent of those infected, according to the US Centers for Disease Control and Prevention. Those who survive often have long-term, progressive neurological difficulties.
“Today’s news is evidence of the significant risk from EEE and we are asking residents to take this risk very seriously,” Dr. Monica Bharel, the state’s commissioner of public health, said in a statement. “We will continue to monitor this situation and the impacted communities.”
The cities and towns considered at critical risk are Acushnet, Carver, Freetown, Lakeville, Marion, Middleborough, New Bedford, Rochester, and Wareham.
Another 15 Southeastern Massachusetts communities are considered to be at high risk, officials said, and 18 more towns and cities are at moderate risk.
In Carver, town officials have banned outdoor activities from dusk to dawn for more than two weeks out of concern about the virus.
“We did that immediately, as soon as the announcement was made . . . that we were at moderate risk,” Arthur F. Borden, chairman of the Carver Board of Health, said by phone Saturday. “We haven’t had to do that since the last go-’round with triple-E.”
Borden said that in conversations with Carver residents and exchanges on social media, he has heard about a great deal of mosquito activity in town this summer.
“Everybody seems to have the same complaint: They can’t go outside a couple of minutes without mosquitoes all over them,” he said.
Kirby Gilmore, town moderator for Rochester, said he hasn’t seen excessive mosquito activity there yet, but after wet weather earlier in the summer, he is bracing for an uptick.
“The months of August and September, that’s the time that this particular species of mosquito is usually a problem, not earlier in the summer,” Gilmore said. “Those are months we have to be cognizant and careful.”
Gilmore said he could recall one human case of the virus in Rochester, many years back.
On Tuesday, state officials announced that areas of Plymouth and Bristol counties would be aerially sprayed to control the mosquito population. That spraying was expected to continue through the weekend, in the evenings and overnight.
Residents in the critical risk areas should still use mosquito repellent and consider staying indoors between dusk and dawn to reduce mosquito exposure, officials said.
Everyone, regardless of where they live, can help protect themselves from mosquito-borne illnesses by using insect repellents containing the ingredients DEET, permethrin, picaridin, or oil of lemon eucalyptus; wearing long sleeves and pants; and avoiding the outdoors during peak biting hours, officials said.
They also encouraged residents to drain standing water around their homes, keep window and door screens in good repair, and protect their pets by flushing out water troughs or dishes, and by using repellent or bringing the animals indoors.
Massachusetts previously saw outbreaks the virus from 2004 to 2006 and 2010 to 2012. In those periods, there were 22 reported cases of infected humans, including 14 residents of Plymouth and Bristol counties.