Eastern Equine Encephalitis has been a constant threat to South Coast residents this summer, and on Friday, Mattapoisett was put on “high alert” when mosquitoes were found carrying the disease.

Although only a handful of EEE cases have been reported across the state this summer, the disease’s high mortality rate, which causes swelling of the brain, is particularly dangerous.

People under 15 and over 50 are at greatest risk for serious illness if they contract EEE.

In Rochester, the alert was also raised to “critical” on Monday, following the death of a horse from EEE.

In Marion, the level has been raised to “high.”

“Most people don’t walk away without some disability, if it doesn’t kill them,” said Mattapoisett Board of Health Agent Dale Barrows.

Burrows said the Board of Health has been testing mosquitoes twice a week all summer, but Friday was the first time EEE was found.

Although mosquitoes with EEE have just been discovered, Burrows said, “Living in Massachusetts, people should be pretty used to it. We have to assume it’s been around.”

Residents from the three towns have been advised to stay indoors from dusk to dawn when mosquitoes are most active.

Barrows said, “In 2009, we had a similar situation, but it was a lot earlier in the summer. This is relatively late.”

Mattapoisett resident Kristen Boucher said she’s been vigilant with repellent all summer and has kept her three-year-old daughter Mila covered up when they go outside.

In light of the curfew, the Bouchers have also moved their evening walks to earlier in the day.

“The curfew is probably best, in particular for residents with young children,” she said.

“It’s a small chance that you could be bit by a mosquito that has EEE, but it could be life or death.”

While residents may opt to ignore the curfew, all outdoor events on town-owned property in the three towns have been prohibited during peak hours.

That means home games at Old Rochester Regional, Tabor Academy and Old Colony Regional Vocational Technical High School will have to be adjusted to an earlier time.

“The games have all been moved at the high school to make sure that they stay within that time frame,” said Superintendent Doug White.

Threat levels will go down after the first frost, said Barrows.

To mitigate the risk before that, Plymouth County Mosquito Control conducted ground spraying in Marion and Rochester Wednesday morning are will spray Mattapoisett starting Friday, September 17.

Anthony Texeira, Superintendent of Mosquito Control, said spraying will be conducted between 3 a.m. and 6 a.m.

For those concerned about negative effects of the pesticide, Texeira said there’s no reason to worry.

“It dissipates in sunlight and leaves no residue,” he said.

“Most of the people in the community are unaware that we even did it.”

Texeira added that the pesticides should not negatively affect pets.

“The flea collar on the dog is more toxic than what we’re spraying,” he said.

Questions should be directed to Mosquito Control at 781-585-5450, the Mattapoisett Board of Health at 508-758-4100, ext. 8 or Rochester and Marion’s Board of Health Director at 508-748-3533.