West Nile Virus Confirmed In Massachusetts For First Time This Year

BOSTON, MA - West Nile virus has been detected for the first time in Massachusetts this year, the state's Department of Public Health announced Wednesday.

A mosquito sample collected on July 11 in the town of Easton in Bristol County was determined to contain West Nile virus after being analyzed in the Massachusetts State Public Health Laboratory. Spread by infected mosquitoes, WNV causes illnesses ranging from a mild fever to more serious conditions such as encephalitis or meningitis.

“West Nile virus is part of summer in Massachusetts, and we expect to see infected mosquitoes at this time of year,” said Public Health Commissioner Margret Cooke. “Now is the time to start taking steps to avoid mosquito bites. While WNV can cause serious illness, there are things that you can do to protect yourself and your loved ones.”

So far, no human or animal cases of WNV or Eastern equine encephalitis, known as EEE, have been detected so far this year. There is no elevated risk level or risk-level change associated with the laboratory finding.

Between 2011 and 2020, 148 people were reported with WNV infection in Massachusetts, according to the DPH, and seven of these people died. There were 11 human cases of WNV in 2021.

While the disease can affect people of all ages, those over the age of 50 are at higher risk for severe disease. While most people who are infected will not have symptoms, those who do will have symptoms similar to the flu, including fever, headaches, body aches, vomiting, diarrhea and rash, according to the Centers for Disease Control and Prevention.

“Simple actions can help protect you from mosquito bites and the diseases they can cause,” said Dr. Catherine M. Brown, a state epidemiologist. “Use a mosquito repellent with an EPA-registered ingredient, wear clothing to reduce exposed skin, drain standing water and repair window screens. We also encourage you to make it a habit to check the mosquito-borne disease webpages on Mass.gov so you know when and where WNV activity is occurring.”

The department offered tips to avoid mosquito bites, which include:

• Using a repellent with an EPA-registered ingredient such as DEET (N,N-diethyl-m-toluamide), permethrin, picaridin (KBR 3023), oil of lemon eucalyptus (p-Menthane-3,8-diol (PMD) or IR3535) according to the instructions on the product label. More information on choosing and using repellents safely is included in the MDPH Mosquito Repellents fact sheet which can be viewed online at www.mass.gov/dph/mosquito.
• DEET products should not be used on infants under two months of age and should be used in concentrations of 30 percent or less on older children. Oil of lemon eucalyptus should not be used on children under three years of age.
• Being aware of peak mosquito hours. Dusk until dawn is the prime biting time for mosquitoes. Consider rescheduling outdoor activities that occur during evening or early morning in areas of high risk.
• Wearing long-sleeves, long pants and socks when outdoors will help keep mosquitoes away from your skin.

To safeguard your home, places that contain standing water, where mosquitoes lay their eggs, should be turned over drained or discarded such as buckets and unused plant pots. Clogged roof gutters should be drained and cleaned of leaves and debris. Window screens should be repaired or replaced to prevent mosquitoes from entering the home, and they should fit tightly.

Plastic wading pools and wheelbarrows should be turned over to prevent contamination - particularly after heavy rains. The water in birdbaths should be changed every day. Standing water should be removed from pool covers, and swimming pools should be kept clean and properly chlorinated. Landscaping can also prevent water from pooling.

Animals also can become infected with West Nile virus. To prevent this, the DPH recommends removing sources of standing water and monitoring water troughs. Horse owners should keep their horses in stalls at night to prevent exposure.

Pet owners should also speak with their veterinarian about mosquito repellents approved for use in animals and vaccinations to prevent WNV and EEE. If an animal is suspected of having WNV or EEE, owners are required to report to the Department of Agricultural Resources, Division of Animal Health by calling 617-626-1795, and to the Department of Public Health by calling 617-983-6800.

More information, including all WNV and EEE positive results, can be found on the Arbovirus Surveillance Information web page at the state's mosquito-borne diseases page, which is updated daily, or by calling the DPH Division of Epidemiology at 617-983-6800.