Season’s first West Nile virus-positive mosquito sample detected in Boston

Mosquitoes carrying the West Nile virus (WNV) were detected in Boston for the first time this year.

The Department of Public Health confirmed that the virus was found in a mosquito sample collected July 6 in Brookline.

“We often find the first evidence of WNV in mosquitoes at about this time every year,” said DPH Commissioner Robert Goldstein.

There were 10 human cases of the virus in 2022. No human or animal cases have been detected so far this year.

West Nile virus is usually transmitted to humans through the bite of an infected mosquito. While it 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, symptoms tend to include fever and a flu-like illness. In rare cases, more severe illness can occur.

“With the recent rain and the warmer weather, mosquito populations will increase and we will start to see more of them carrying WNV,” said state epidemiologist Catherine M. Brown. She suggested several steps that could reduce potential exposure to the virus:

Avoid mosquito bites

Apply insect repellent when outdoors. Use a repellent with an EPA-registered ingredient Be aware that repellent 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, as mosquitoes lay their eggs there and check to see where water might pool in areas around your home, like unused flowerpots or wading pools. If you have a birdbath, change the water frequently. Keep mosquitoes outside by having tightly fitting screens on all of your windows and doors.

Protect your animals

Make sure you drain any containers or troughs your animals use on a regular basis.  Water troughs especially 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. Talk to your vet about animal-approved mosquito repellents, and any vaccinations that are available to protect your pets or livestock.


Irina Matchavariani WBUR Newsroom Fellow
Irina Matchavariani is a newsroom fellow at WBUR.



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