West Nile Virus Detected In Chatham; Orleans Risk Also Elevated

CHATHAM – For the first time since public health officials began a testing program, West Nile virus has been detected in Chatham. 

The virus was found in a sample of mosquitoes collected in town on Aug. 18. As a result, the Massachusetts Department of Public Health has raised the official risk for transmission of the disease in Chatham from "low" to "moderate."

 Orleans and Eastham are also classified as having “moderate” risk of transmission after a positive sample was collected in south Eastham on Aug. 6. There have been no human or animal cases of West Nile virus (WNV) reported in Barnstable County this year.

 WNV is transmitted to people through mosquito bites, though most infected people show no symptoms. About 20 percent of those infected get mild flu-like symptoms, and a small percentage of people become seriously ill with a high fever, neck stiffness, muscle weakness, confusion or tremors. The risk is higher for people over 50 years of age, and no medicines are available to treat West Nile. 

Between 2001 and 2025, 273 people were reported with WNV infection in Massachusetts. Twenty died. Last week, the state announced this year's first human case of West Nile in a man in his 90s who was exposed in Middlesex County. The second case was reported Monday in a man in his 60s, also in Middlesex County.

Crews with the Cape Cod Mosquito Control Project were deployed to Chatham Thursday and Friday to treat storm drains and containers holding standing water in areas around the positive sample.

Gabrielle Sakolsky, superintendent of Cape Cod Mosquito Control, said a crew was dispatched to Chatham Thursday “as soon as we had a suspected positive.” Treatments were taking place in various parts of town, including around Stage Harbor.

 “We start treatments in the areas that are most likely to have people outside at night, and then move on to the neighborhoods,” she said. “The crew was checking for mosquitoes and applying larvicide in the area around the positive sample.”

 WNV has been previously detected on the Upper Cape and in other Cape towns, as well as in rural and urban areas in other parts of the state. The risk factor in Brewster and Harwich remains low, though Mosquito Control crews were working in Harwich Friday.

 To reduce the risk of exposure to mosquito bites, people are urged to limit outdoor activity from dusk to dawn, to apply insect repellent, and to wear clothing that covers the skin. But one of the most effective ways to control mosquitoes is to limit their ability to breed. And given the rain the area received over the weekend, that’s a primary concern.

 “The challenge with the rain is all the containers and blocked gutters on properties that will fill with water,” Sakolsky said. “The mosquitoes that transmit West Nile Virus lay their eggs in manmade containers, so reminding folks to go around their property and empty containers after the rain is really important.” Around the home, experts advise draining standing water in gutters, drains, watering cans and other containers, and changing the water in birdbaths at least twice a week.

 The Cape Cod Mosquito Control Project was organized in 1928, making it the first organized mosquito control project in the state. At the time, clouds of mosquitoes threatened the region’s ability to become a popular tourist destination. During the 1930s, its crews dug about 1,500 miles of drainage systems for salt water mosquito control, and installed sluiceways, dams and dikes to control inland water areas. There are a total of almost 35,200 acres of potential mosquito breeding habitat on Cape Cod, according to the Mosquito Control Project website.

This article has been updated.