Public health officials on Friday said a third Massachusetts resident has tested positive for eastern equine encephalitis, a mosquito-borne virus, prompting more communities to see their risk levels raised to critical.

The Department of Public Health announced Friday that a man over the age of 60 had contracted the virus in northern Franklin County, making him the third person in the state this year with a confirmed case of EEE.

The other two human cases were detected in southern Plymouth County and eastern Worcester County.

As a result of the latest confirmation, the state designated the towns of Heath and Colrain at critical risk. One horse each in Worcester County towns of Mendon and Uxbridge also tested positive for the virus, so public health officials increased those communities to the critical risk category as well.

DPH and the Department of Agricultural Resources previously announced aerial spraying to combat mosquitoes in portions of Worcester and Middlesex Counties will begin Sunday.

Another round will continue in southeastern Massachusetts over the weekend. A total of 23 communities are at critical risk for the EEE virus, with another 22 at high risk and 52 at moderate risk. This year's human cases are the first confirmed in Massachusetts since 2013

Information from State House News Service

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