A third human case of eastern equine encephalitis has been diagnosed in a Massachusetts man, the Massachusetts Department of Public Health said. The patient is a man over the age of 60 who was exposed to the virus in northern Franklin County, health officials said. The risk level in two communities in Franklin County has been raised to critical as a result. In addition, one horse from Mendon and one horse from Uxbridge have also tested positive for the EEE virus, raising the risk level to critical in two additional communities in Worcester County, health officials said. The four communities now at critical risk are Heath and Colrain in Franklin County, and Mendon and Uxbridge in Worcester County. Earlier this week, DPH and the Department of Agricultural Resources announced aerial spraying in specific areas of Worcester and Middlesex counties scheduled to begin Sunday Aug. 25, weather permitting, continuing for several evenings. As a result of the elevated risk in several communities, the spray zone is being expanded. The additional communities either partially or fully in the spray zone are Blackstone, Douglas, Dudley, Holliston, Hopedale, Mendon, Millville, Oxford, Uxbridge and Webster. Additionally, MDAR is currently conducting a second round of aerial spraying in areas of Southeastern Massachusetts which began on Aug. 21 and is expected to continue through the weekend. "We are seeing the most intense level of EEE activity that we have in several years. The largest area is in Bristol and Plymouth Counties with a second focus of activity in parts of Worcester and Middlesex Counties," said Public Health Commissioner Monica Bharel, MD, MPH. "We are urging people across the state to remember that the peak time for transmission of mosquito-borne illness extends through September here in Massachusetts."In total across Massachusetts, there are 23 communities now at critical risk, 22 at high risk, and 52 at moderate risk for the EEE virus.EEE is a rare but serious and potentially fatal disease that can affect people of all ages. EEE occurs sporadically in Massachusetts with the most recent outbreak years occurring from 2004-2006 and 2010-2012. There were 22 human cases of EEE infection during those two outbreak periods with 14 cases occurring among residents of Bristol and Plymouth Counties.EEE virus has been found in 330 mosquito samples this year, many of them from species of mosquitoes capable of spreading the virus to people.Because of the EEE concerns, the Massachusetts Department of Conservation and Recreation is canceling evening programming in several state parks.