Sixth human case of West Nile virus recorded in Massachusetts this year, health officials say

BOSTON — A Massachusetts man in his 70s has become the sixth human case of West Nile virus in the state this year, state public health officials said Wednesday.

The man was likely exposed in Middlesex County, state Department of Public Health officials said in a statement.

The risk of human infection with West Nile virus is moderate in parts of greater Boston (Middlesex, Norfolk, and Suffolk counties), and in parts of Berkshire, Bristol, Hampden, Hampshire, Plymouth, and Worcester counties, officials said. No risk level changes are associated with this recent case.

Although temperatures are starting to fall, some risk from mosquito-borne disease will continue until all areas have had a hard frost, often considered to be when temperatures fall below 28 degrees.

People should continue to take steps to avoid mosquito bites when outdoors, officials said.

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 West Nile virus can infect people of all ages, people over the age of 50 are at higher risk for severe disease.

Most people infected with the virus will have no symptoms. When present, West Nile virus 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.

This is a developing story. Check back for updates as more information becomes available.

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