First 2 Human West Nile Cases In MA: See Where Risk Is Highest

MASSACHUSETTS — The state has confirmed the first two human cases of West Nile virus this summer, although one of the cases was contracted outside in another state, according to the Massachusetts Department of Public Health.

The two cases follow numerous positive West Nile mosquito samples confirmed in recent months, prompting state officials to raise the risk level in communities around Boston, Framingham, Springfield, Pittsfield and Plymouth.

A man in his 40s likely contracted West Nile in Middlesex County, state officials said, and a woman in her 70s is the out-of-state case. Eight human cases were confirmed in 2022.

"August and September are the months when most people are exposed to West Nile virus in Massachusetts. Populations of mosquitoes that can carry and spread this virus are fairly large this year, and we have seen recent increases in the number of WNV-positive mosquito samples from multiple parts of the Commonwealth," Public Health Commissioner Dr. Robert Goldstein said Tuesday.

Residents over age 50 are at highest risk of developing a West Nile illness from mosquito bites. The disease can cause flu-like symptoms, and some people will have no symptoms at all. About one out of every 150 people may develop either encephalitis or meningitis, which can lead to central nervous system damage and death. About one in every 10 people who develop the more severe form of West Nile die, according to the Centers for Disease Control.

The best way to prevent a West Nile infection is to protect yourself against mosquito bites, state health officials said. Safety measures can include using mosquito spray containing DEET, treating clothes with permethrin, avoiding peak mosquito hours around dawn and dusk and wearing pants and long sleeves. Homeowners should also drain standing water to prevent mosquitoes from breeding.

Eastern Equine Encephalitis, the other main mosquito-borne threat in Massachusetts, has not been detected in any mosquito sample so far this summer. The risk of contracting EEE is either low or remote in every community in the state, according to DPH.

Residents can view EEE and West Nile risk maps on the DPH website.