State Health Officials Announce Risk-level Changes for West Nile Virus

BOSTON — The Massachusetts Department of Public Health (DPH) announced that, due to ongoing evidence of mosquitoes carrying West Nile virus (WNV), eight municipalities are now considered to be at high risk from the virus. This elevated risk level applies to Boston in Suffolk County and Abington, Brockton, East Bridgewater, Marion, Mattapoisett, Rochester, and Whitman in Plymouth County.

The first WNV-positive mosquitoes in Massachusetts this year were announced on July 2 from Quincy. A total of 262 WNV-positive mosquito samples so far this year have been detected from Barnstable, Berkshire, Bristol, Dukes, Essex, Hampden, Middlesex, Norfolk, Plymouth, Suffolk, and Worcester counties. The risk of human infection with WNV is moderate throughout Bristol, Norfolk, and the rest of Plymouth County and in parts of Barnstable, Berkshire, Essex, Hampden, Middlesex, Plymouth, and Worcester counties.

“We are finding evidence of West Nile virus in mosquitoes in multiple parts of the Commonwealth,” Public Health Commissioner Dr. Robbie Goldstein said. “While most people do not get severely ill from WNV, it is still important to take it seriously. People at greatest risk for severe disease from WNV infection include those over 60 years of age and people with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and people who have received organ transplants.”

WNV is usually transmitted to humans through the bite of an infected mosquito. There were six human cases of WNV in 2023. There have been two human and no animal cases of WNV confirmed this year so far.

“The risk from WNV is pretty widespread this year,” State Epidemiologist Dr. Catherine Brown said. “In addition to recommending that people use mosquito repellent with an EPA-registered active ingredient and clothing to reduce exposed skin, check your window screens to be sure they don’t have holes, and empty any containers that accumulate water around your yard.”