A rare but deadly disease spread by mosquitoes has nearly a dozen Massachusetts communities on alert, prompting some towns to close parks after dusk, restrict outdoor activities and reschedule public events.

This 2014 photo made available by the U.S. Centers for Disease Control and Prevention shows a feeding female Anopheles gambiae mosquito. James Gathany/CDC via Associated Press file

Massachusetts health officials this month confirmed the state’s first human case of the eastern equine encephalitis virus this year – a man in his 80s exposed in Worcester County, west of Boston. Ten communities are now designated at high or critical risk for the virus, the health agency said Saturday. Plymouth, about 40 miles south of Boston, closed all public parks and fields from dusk until dawn. Nearby, Oxford banned all outdoor activities on town property after 6 p.m.

“We have not seen an outbreak of EEE for four years in Massachusetts,” Robbie Goldstein, the state’s Department of Public Health commissioner, said in a statement. “We need to use all our available tools to reduce risk and protect our communities. We are asking everyone to do their part.”

Eastern equine encephalitis is caused by a virus spread through the bite of an infected mosquito, according to the Centers for Disease Control and Prevention. It is rare, but serious: about 30% of people with the virus die, and many survivors suffer ongoing neurological problems.

The virus outbreak in Massachusetts comes as mosquito season has lengthened across the United States, The Washington Post reported. Climate change has fueled rising global temperatures, and for more than two-thirds of the United States, increased the number of “mosquito days,” meaning days with an average humidity of at least 42% and temperatures between 50 and 95 degrees.

The Northeast has warmed faster than the rest of the country and experienced the biggest increase in mosquito days. In Massachusetts, there have been an average of 14 more mosquito days compared with the period from 1980 to 2009.

Scientists warn that longer mosquito seasons could heighten the risk of outbreaks of diseases carried by the bloodsucking insects, such as dengue and malaria.

Massachusetts health officials said there will be mosquito spraying between dusk and dawn throughout this week in Plymouth and Worcester counties to limit the presence of eastern equine encephalitis.

“Aerial spraying will target mosquitoes carrying the EEE virus. While these measures are crucial for reducing transmission risk, it’s vital for everyone to stay vigilant and follow personal protection guidelines to safeguard our community,” Massachusetts Department of Agricultural Resources Commissioner Ashley Randle said in a statement.

Residents are urged to use mosquito repellents, drain standing water around their homes, wear clothing that covers their skin, and reschedule outdoor activities to avoid the hours between dusk and dawn.

Symptoms of those infected with the virus can include fever, headache, vomiting, diarrhea, seizures, behavioral changes and drowsiness. There are no vaccines to prevent eastern equine encephalitis, nor is there a specific treatment.

In 2019, there were 12 human cases of the virus in Massachusetts. Six people died. The next year, there were five human cases, with one death, according to the state health agency.

In a Wednesday memo, Oxford’s town manager, Jennifer M. Callahan, said she has been in touch with the family of the person who was afflicted with the virus this year and still battling it in the hospital.

The family “explained their loved one with EEE was the one person in the family who recounted through the years they never get bit by mosquitos,” Callahan said. “However, right before he became symptomatic he shared that he had been recently bitten.”

“They want people to be aware this is an extremely serious disease with terrible physical and emotional consequences, regardless if the person manages to live,” Callahan said.