First human case of West Nile virus reported in Massachusetts this season

A woman in her 70s has contracted West Nile virus (WNV), marking the first human case in Massachusetts of the season, state health officials announced Tuesday.

The virus is typically transmitted through bites from infected mosquitoes, and the woman was exposed in Middlesex County, the Department of Public Health said. The risk of WNV is high in 10 municipalities in Suffolk and Middlesex counties, and the risk level is moderate in 193 municipalities throughout the state.

"West Nile virus can be a very serious disease and its presence in mosquitoes remains high right now in Massachusetts," DPH Commissioner Robbie Goldstein said. "While September brings cooler air and the return to school for many in the state, the risk from WNV is going to be elevated for some time. Residents should continue to take precautions to avoid mosquito bites."

The majority of people infected with WNV won't experience symptoms, though some individuals could have a fever, headache, body aches, nausea, vomiting, swollen lymph glands and skin rashes, according to a DPH webpage. People ages 50 and older are at greater risk of developing severe illness.

DPH said there have no human or animal cases yet of Eastern equine encephalitis, which is also transmitted through mosquito bites.

People are urged to apply insect repellent, wear long clothing to reduce the chance of bites, consider rescheduling activities during peak mosquito hours, drain standing water around their homes, and install or repair screens.

"The mosquitoes will be with us until the first hard frost,” said state epidemiologist Catherine Brown.