By CBSBoston.com Staff

BOSTON (CBS) — A man in his 50s and a man in his 70s are now the latest human cases of West Nile Virus in Massachusetts this year. The state said both men were exposed to the virus in Middlesex County.

The Department of Public Health had just announced Wednesday that the first human case in the state this year was a woman in her 80s from Middlesex County. She was likely exposed there.

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“These are the second and third human cases of West Nile virus infection in Massachusetts this year and we are seeing significant expansion of virus activity in mosquitoes,” said Acting Public Health Commissioner Margret Cooke. “Risk from West Nile virus will continue until the first hard frost.”

Prior to Thursday, the Greater Boston area and several towns in Bristol and Worcester counties were already deemed to be at moderate risk for the West Nile Virus. With the recent human cases popping up, 38 additional counties went from low to moderate risk.

The full list of communities to be at risk is available here.

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Last year, there were just five human cases of the virus in Massachusetts.

The virus is usually spread through bites from infected mosquitos. It can cause a mild fever or more serious diseases like encephalitis or meningitis.

Most people infected will have no symptoms but people over 50 are at higher risk for severe disease, according to DPH.

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West Nile Virus was first identified in the U.S. in 1999.

CBSBoston.com Staff