Another person has been infected with EEE in the Bay State, as local officials urge residents to keep using insect repellent and “avoid peak mosquito biting hours.”

The Massachusetts Department of Public Health on Monday announced a fourth human case of Eastern Equine Encephalitis in the state this year.

The case is a man in his 50s who was exposed in a part of Middlesex County that’s at high risk for EEE.

The region is facing a major outbreak of mosquito-borne diseases this season. Recently, a man in New Hampshire died from EEE.

“This year’s EEE season has been particularly active and is generating a lot of concern in communities across Massachusetts,” said Public Health Commissioner Robbie Goldstein. “While EEE remains a rare disease, the risk level is elevated in multiple communities.

“With the weather forecast showing warm, sunny weather for the rest of the week, we recommend that people take necessary precautions in areas of elevated risk,” Goldstein added. “This includes recommending that residents and towns in areas at high risk for EEE reschedule their evening outdoor events to avoid peak mosquito biting hours from dusk to dawn.”

There have been 91 EEE-positive mosquito samples in Massachusetts this year.

While most activity has been focused in Plymouth and Worcester counties, infected mosquitoes have also been found in Bristol, Essex, and Middlesex counties.

EEE is transmitted to humans through the bite of an infected mosquito. The last outbreak of EEE in Massachusetts occurred in 2019-2020, and resulted in 17 human cases with seven deaths.

In addition to this year’s four human cases, EEE has also been identified in two horses in Massachusetts.

Health officials are urging residents to put on bug spray, reschedule outdoor activities that occur during evening or early morning in areas of high risk, and wear long sleeves, long pants and socks when outdoors to help keep mosquitoes away from your skin.