3 New MA West Nile Virus Cases Confirmed As Mosquito-Borne Illness Worries Escalate

MASSACHUSETTS — Three more human cases of West Nile virus cases were confirmed in Massachusetts on Tuesday as the state deals with one of its biggest mosquito-borne illness breakouts in years late in the summer.

The new West Nile virus cases make it 10 across Massachusetts this season and are in addition to the four confirmed human cases of Eastern equine encephalitis the state Department of Public Health confirmed as of Monday.

• Fourth Human EEE Case Confirmed In MA In Worst Outbreak In 5 Years

"West Nile virus does not always raise as much concern as EEE, but it remains a potentially very serious disease, especially for those over the age of 60 or with certain medical conditions, such as cancer, diabetes, high blood pressure, kidney disease, or an organ transplant," said Public Health Commissioner Robbie Goldstein, MD, PhD. "I encourage everyone to take measures to protect themselves: use mosquito repellent with an EPA-registered active ingredient when outdoors, wear long sleeves and pants, and be aware of peak mosquito hours."

All three of the new WNV cases are in people in their 60s. One is a woman who was exposed in southern Bristol County. The second is a man in his 60s who was exposed in Suffolk County in an area already at high risk. The third is a man who was exposed in Barnstable County.

WNV risk levels in the following communities are being raised to high: Barnstable, Mashpee, Sandwich, and Yarmouth in Barnstable County; and Acushnet, Dartmouth, and New Bedford in Bristol County.

There have been 302 WNV-positive mosquito samples so far this year detected from Barnstable, Berkshire, Bristol, Dukes, Essex, Franklin, Hampden, Middlesex, Norfolk, Plymouth, Suffolk, and Worcester counties. There were six human cases of WNV and no animal cases in 2023.

No animal cases of WNV have been detected so far this year.

The last outbreak of EEE in Massachusetts occurred in 2019-2020 and resulted in 17 human cases with seven deaths. In addition to this year's four human cases, EEE has also been identified in two horses in Massachusetts.

EEE is transmitted to humans through the bite of an infected mosquito.

Residents throughout the state are advised to avoid going outdoors, especially in wooded areas, around the hours of dusk and dawn when mosquito activity is highest and to wear long clothing when out at those times.

The state DPH advised the use of a repellent with DEET, permethrin, picaridin or oil of lemon eucalyptus, according to the instructions on the product label.

Residents are also asked to clear standing water on properties that can be used as mosquito breeding areas.

(Scott Souza is a Patch field editor covering Beverly, Danvers, Marblehead, Peabody, Salem and Swampscott. He can be reached at Scott.Souza@Patch.com. X/Twitter: @Scott_Souza.)