BOSTON — Massachusetts health officials are raising the state’s risk level for West Nile Virus after the fourth case of the disease was found in a resident this year.
The fourth case was found in a man in his 60s from Norfolk County, the Massachusetts Department of Health says.
In response to the additional case, 12 municipalities, Ashland, Holliston, Hopkinton and Sherborn in Middlesex County, and Dover, Medfield, Medway, Millis, Norfolk, Norwood, Walpole, and Westwood are now at a “moderate” risk level for the mosquito-borne disease.
“With the weather getting cooler, mosquito activity will start to be reduced and the risk of West Nile virus will decrease, though some risk of mosquito-borne disease will continue until the first hard frost,” said Public Health Commissioner Robert Goldstein.
Most of the Greater Boston area and parts of Berkshire, Bristol, Hampden, Hampshire, Plymouth, and Worcester counties were already considered to be at moderate risk.
In 2022, there were eight human cases of West Nile virus infection identified in Massachusetts.
The virus is usually transmitted to humans through the bite of an infected mosquito. While the virus can infect people of all ages, people over the age of 50 are at higher risk for severe disease. Most people infected with West Nile virus will have no symptoms. When present, symptoms tend to include fever and flu-like illness. In rare cases, more severe illness can occur.
State health officials offered the following tips to protecting you and your family illnesses caused by mosquitoes:
Avoid Mosquito Bites
Apply Insect Repellent when Outdoors. Use a repellent with an EPA-registered ingredient (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. 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.
Be Aware of Peak Mosquito Hours. The hours from dusk to dawn are peak biting times for many mosquitoes. Consider rescheduling outdoor activities that occur during evening or early morning in areas of high risk.
Clothing Can Help Reduce Mosquito Bites. Wearing long-sleeves, long pants, and socks when outdoors will help keep mosquitoes away from your skin.
Mosquito-Proof Your Home
Drain Standing Water. Mosquitoes lay their eggs in standing water. Limit the number of places around your home for mosquitoes to breed by draining or discarding items that hold water. Check rain gutters and drains. Empty unused flowerpots and wading pools and change the water in birdbaths frequently.
Install or Repair Screens. Keep mosquitoes outside by having tightly fitting screens on all windows and doors.
Protect Your Animals
Animal owners should reduce potential mosquito breeding sites on their property by eliminating standing water from containers such as buckets, tires, and wading pools – especially after heavy rains. Water troughs provide excellent mosquito breeding habitats and should be flushed out at least once a week during the summer months to reduce mosquitoes near paddock areas. Horse owners should keep horses in indoor stalls at night to reduce their risk of exposure to mosquitoes. 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 Mosquito-borne Diseases | Mass.gov, which is updated daily, or by calling the DPH Division of Epidemiology at 617-983-6800.
This is a developing story. Check back for updates as more information becomes available.
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