A mosquito in Swampscott has tested positive for West Nile Virus, though the town remains at a low risk level.
West Nile Virus is most commonly transmitted to humans through the bite of an infected mosquito. Mosquitoes become carriers of the virus after feeding on infected birds. Mosquitoes carrying the virus are common throughout Massachusetts and can be found in both urban and rural areas. As of now, no human cases of West Nile Virus have been reported in Massachusetts, according to the Department of Public Health.
“West Nile virus occurs every year in Massachusetts. Although it is generally most common in urban and suburban areas, the extent to which the virus is distributed in mosquitoes varies based on recent weather patterns, mosquito populations and the presence of infected birds,” Omar Cabrera, who is a part of the communications office at the Massachusetts Department of Public Health, told the Swampscott Tides. “Finding West Nile Virus in mosquitoes in Swampscott is an indicator that this virus is widespread this year and a reminder to everyone to take steps to prevent mosquito bites when spending time outdoors.”
Although West Nile Virus can affect people of all ages, those over 50 face a higher risk of severe illness. According to 2023 U.S. Census Bureau data, Swampscott’s median age is 45.3, with nearly 6,600 residents over 50.
Mosquitoes are most active from dusk to dawn, when biting is most likely to occur.
“When risk is increased, consider rescheduling outdoor activities that occur during the evening or early morning. If you are outdoors at any time and notice mosquitoes around you, take steps to avoid being bitten by moving indoors, covering up and/or wearing repellant,” the Swampscott Health Department advises.
The Swampscott Health Department recommends using insect repellent when spending time outdoors. A repellent with DEET (N, N-diethyl-m-toluamide), permethrin, picaridin (KBR 3023), IR3535 or oil of lemon eucalyptus [p-methane 3, 8-diol (PMD)] is recommended.
However, DEET should not be used on infants under two months old and should be limited to concentrations of 30% or less for older children. Oil of lemon eucalyptus should also not be used on children under three years old.
Wearing long-sleeved shirts, pants, and socks can also help reduce mosquito bites by limiting skin exposure.
“The best way to reduce your risk is to use mosquito repellent according to the directions on the label and reduce their access to exposed skin using long sleeves and pants,” Cabrera told the Swampscott Tides.
To reduce mosquito breeding, the Swampscott Health Department advises draining standing water – such as wading pools, flower pots, and birdbaths – where mosquitoes often lay eggs. Installing screens on doors and windows can help keep mosquitoes out of the home.
According to the Centers for Disease Control and Prevention (CDC), symptoms of West Nile Virus can include fever, headache, body aches, vomiting, diarrhea, or a rash. About one in five people, or 20%, who are infected develop a fever and other symptoms. About one in 150 infected people, or .67%, develop a serious and sometimes fatal illness.
There is currently no vaccine or specific treatment for West Nile Virus in humans.
As of August 12, the CDC has reported 219 cases of West Nile Virus in 2025, across 29 states.
In Massachusetts, 10 cities and towns – including Dracut, Lowell, Chelmsford, and Boston – are currently listed as high risk by the Department of Public Health. Nearby, Salem and Marblehead remain at low risk, while Lynn and Peabody are currently at moderate risk.
Last year, 19 human cases of West Nile Virus were confirmed in Massachusetts.
Updated August 18 at 6 p.m. with comment from the Department of Public Health.
