Viruses detected in Tri-Town mosquitoes are making the bothersome insects more harmful than usual.

On Friday, Aug. 23, the Massachusetts Department of Public Health declared that Mattapoisett, Marion and Rochester are three of eight municipalities currently at high risk of the West Nile virus, a disease carried by mosquitoes.

“We are finding evidence of West Nile virus in mosquitoes in multiple parts of the Commonwealth,” said Public Health Commissioner Robbie Goldstein. “While most people do not get severely ill from WNV, it is still important to take it seriously. People at greatest risk for severe disease from WNV infection include those over 60 years of age and people with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and people who have received organ transplants.”

According to the state, there have been two confirmed cases of West Nile Virus being transmitted to humans in 2024, after six in 2023.

Along with the West Nile virus, EEE is also a threat in the Tri-Town.

The town of Marion canceled its annual town party set for Saturday, Aug. 24, after mosquitoes with West Nile virus and Eastern equine encephalitis were found earlier in August.

EEE is a rare but serious and sometimes fatal mosquito-borne disease, with symptoms including high fever, stiff neck, headache and lack of energy, according to the Department of Public Health.

Encephalitis, or swelling and inflammation of the brain, is the most frequent serious complication. About half of those infected with the disease in Massachusetts have died, the Department of Public Health said.

Marion, Mattapoisett and Rochester are all currently at moderate risk to EEE, according to the state.

The state of Massachusetts will be spraying repellent in Rochester and other Plymouth County towns starting on Tuesday, Aug. 27.

Spraying begins at dusk and will end by dawn each day. Planes spotted overhead at dusk in the spray zones are either conducting the aerial spray or preparing to do so, according to the Department of Public Health.

Marion was also sprayed for mosquitos via truck by the Plymouth County Mosquito Control Project earlier in August.

More information is available on town websites and mass.gov/orgs/department-of-public-health.