State Health Officials Announce First Two Human Cases of West Nile Virus

BOSTON — The Massachusetts Department of Public Health (DPH) announced the first two human cases of West Nile virus (WNV) in state residents this year. One individual is a female in her 70s who was exposed to the virus in another part of the country. The second individual is a male in his 40s who was exposed in Middlesex County, an area already known to be at moderate risk.

The risk of human infection with WNV is moderate in the Greater Boston area (Middlesex, Norfolk, and Suffolk counties) and in parts of Berkshire, Bristol, Hampden, Hampshire, Plymouth, and Worcester counties. There are no additional risk level changes indicated at this time.

“This is the first time that West Nile virus infection has been identified in Massachusetts residents this year,” Public Health Commissioner Dr. Robert Goldstein said. “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.”

In 2022, there were eight human cases of WNV infection identified in Massachusetts. WNV is usually transmitted to humans through the bite of an infected mosquito. While WNV can infect people of all ages, people over the age of 50 are at higher risk for severe disease. Most people infected with WNV will have no symptoms. When present, WNV symptoms tend to include fever and flu-like illness. In rare cases, more severe illness can occur.

“We are coming to the unofficial end of summer, but mosquitoes with West Nile virus will persist for several more months,” said Dr. Catherine Brown, state epidemiologist. “To avoid mosquito bites, use a repellent with an EPA-registered ingredient, wear clothing to reduce exposed skin, drain standing water, and repair window screens. We also encourage everyone to regularly visit DPH’s mosquito-borne-diseases webpages to stay informed on when and where WNV activity is occurring.”