A patient who contracted the eastern equine encephalitis virus died at Tufts Medical Center, the hospital confirmed Monday, in what state officials described as the fourth human case of the mosquito-borne illness identified in Massachusetts this summer.

The Department of Public Health announced Sunday that a woman from southern Bristol County in her 50s had contracted EEE, making her the fourth confirmed person with the virus.

State officials did not acknowledge the woman's death, but a spokesman for the hospital briefly told the News Service on Monday that a patient had died due to the EEE virus. Public Facebook posts from family members and from the Teamsters Local 59 union identified the victim as Laurie Sylvia of Fairhaven.

The death appears to be the first from EEE in Massachusetts this year.

Three other human cases have been confirmed, according to the DPH: a man older than 60 in northern Franklin County, a man older than 60 in southern Plymouth County and a man between 19 and 30 in eastern Worcester County.

Two cases have been detected in horses in Mendon and Uxbridge as well. As of Friday, when the third case was confirmed, 23 communities were designated at critical risk for EEE with another 22 at high risk and 52 at moderate risk.

Public health officials say the presence of EEE, which is carried by mosquitoes, is cyclical in Massachusetts. Before this summer, the virus had not been detected in the state since 2013, and the most recent outbreak from 2010 to 2012 saw seven human cases and three deaths.

State workers finished aerial spraying to combat mosquitoes in Bristol and Plymouth counties and will conduct additional sprays this week in Worcester and Middlesex counties. Officials urged the public to take several safety steps as well, including use of insect repellent, wearing long sleeves and minimizing outdoor activity during peak dusk-to-dawn mosquito hours.