Second human case of West Nile virus confirmed in Massachusetts in 2024

The second human case of West Nile virus has emerged in the Commonwealth this year, the Massachusetts Department of Public Health announced Monday afternoon.

A man in his 70s was exposed to West Nile virus in Middlesex County, a moderate-risk area, the department said.

The first human case of West Nile virus was documented on Aug. 6, when someone was exposed in Hampden County, the department said. No animal cases have been found yet.

• Read more: West Nile virus detected in Massachusetts mosquitoes for first time in 2024

The first mosquitoes carrying West Nile virus this year in the Bay State were reported July 2 from a sample collected in Quincy, the department said.

As of Aug. 12, 145 mosquito samples testing positive for West Nile virus had been found in Barnstable, Berkshire, Bristol, Dukes, Essex, Hampden, Middlesex, Norfolk, Plymouth, Suffolk and Worcester counties, according to the department.

The Boston metropolitan area — Middlesex, Norfolk and Suffolk counties — has a moderate risk of human infection with West Nile virus, according to the department. Parts of Barnstable, Bristol, Essex, Hampden, Plymouth and Worcester counties also have a moderate risk.

“Many parts of the country, including Massachusetts, are experiencing increased WNV activity,” Public Health Commissioner Robbie Goldstein said in a statement. “This is the peak of the year when most people are exposed to West Nile virus in Massachusetts. Residents should continue to take precautions to avoid mosquito bites.”

West Nile virus is typically transmitted to humans after they are bitten by an infected mosquito, the department said. In 2023, Massachusetts saw six human cases of West Nile virus.

“It is still summer and the risk of WNV will be elevated for some time,” state epidemiologist Dr. Catherine M. Brown said in a statement. “People should use mosquito repellent with an EPA-registered active ingredient, wear clothing to reduce exposed skin, and consider rescheduling outdoor activities that occur during the evening or early morning hours.”

• Read more: First human case of West Nile virus confirmed in Massachusetts for 2024

The department advises people to protect themselves from mosquitoes and the diseases they carry. Officials say people should use insect repellent when outdoors, reschedule outdoor activities to when mosquitoes bite most — from dusk to dawn — and wear clothing that covers most of the skin when outdoors.

People should also drain any standing water, as mosquitoes are known to lay their eggs there, and install or repair window screens to keep the insects out of their homes, officials said.

The department also encourages people to protect their animals by draining standing water and keeping them indoors to reduce the risk of being bitten.