Mass. health officials report the second human case of West Nile virus this year

The Massachusetts Department of Public Health announced on Monday that it had detected the second human case of West Nile virus in the state this year. 

The virus affected a man in his 70s in Middlesex County, an area the department has marked as a moderate risk.

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

On July 2, officials reported the first West Nile virus-positive mosquitoes in Massachusetts from samples collected in Quincy.

The department says 145 positive mosquito samples have been taken this year from Barnstable, Berkshire, Bristol, Dukes, Essex, Hampden, Middlesex, Norfolk, Plymouth, Suffolk, and Worcester counties. 

The risk of human infection from the West Nile virus remains moderate in the Greater Boston area and parts of Barnstable, Bristol, Essex, Hampden, Plymouth, and Worcester counties. 

Infected mosquitoes usually transmit West Nile virus to humans through their bites. The illness ranges from mild fever to serious diseases like encephalitis or meningitis. 

This year’s first human case was reported on Aug. 6 for a person exposed in Hampden County. There were six human cases of the virus reported in 2023. 

So far, no animal cases of West Nile virus have been detected this year. 

However, earlier this month, the department announced the first animal case of Eastern Equine encephalitis or EEE. The department diagnosed a horse with EEE in Plymouth, which prompted the state to raise the town’s virus risk level to high. 

“It is still summertime and the risk from (West Nile virus) is going to be elevated for some time,” said State Epidemiologist Dr. Catherine M. Brown, in a statement. “People should use mosquito repellent with an EPA-registered active ingredient, clothing to reduce exposed skin, and consider rescheduling outdoor activities that occur during the evening or early morning.”

Some tips to avoid mosquito bites

• Mosquito-proof your home by draining standing water or installing and repairing screens. 

• Apply insect repellent when outdoors. Use repellent with an EPA-registered ingredient, such as DEET, permethrin, picaridin, or lemon eucalyptus oil. 

• Be aware of peak mosquito hours, from dusk to dawn. 

• Wear long sleeves, long pants, and socks when outdoors.