BOSTON — State health officials on Tuesday elevated risk levels for West Nile virus in several Massachusetts communities after two more people have come down with the disease that is spread by mosquitoes.
The two new cases are a man in his 50s who was exposed in Suffolk County and a man in his 80s who was exposed in southern Middlesex County, officials said.
To date, six human cases of West Nile virus have been recorded in Massachusetts this year, officials said. No animal cases of West Nile virus have been detected this year.
As a result, West Nile virus risk levels in the following area communities are being raised to high: Saugus in Essex County; Arlington, Belmont, Malden, Medford, and Melrose in Middlesex County; and Chelsea, Revere, and Winthrop in Suffolk County.
“The risk of West Nile virus in Massachusetts will continue until the first hard frost. While the temperatures may be a bit cooler, September is still within the peak time for West Nile virus activity in Massachusetts,” state Public Health Commissioner Dr. Robbie Goldstein said in a statement. “As we all adjust to our post-summer schedules, one routine that everyone should continue is using mosquito repellent when outdoors.”
So far this year, officials have collected 286 mosquito samples from several counties that were positive for West Nile virus, including in Barnstable, Berkshire, Bristol, Dukes, Essex, Hampden, Middlesex, Norfolk, Plymouth, Suffolk, and Worcester counties.
The risk of human infection with West Nile virus is moderate or high in Greater Boston (Middlesex, Norfolk, and Suffolk counties) and is also elevated in parts of Barnstable, Bristol, Essex, Hampden, Plymouth, and Worcester counties.
West Nile virus is usually transmitted to humans through the bite of an infected mosquito. In 2023, there were six human cases of West Nile virus and no animal cases that year.
News of the additional human cases of West Nile virus in Massachusetts came as the region is grappling with mosquito-born viruses that can turn deadly.
In New Hampshire, a 41-year-old resident who had been infected with Eastern Equine Encephalitis, or EEE, virus has died, state health officials said last week.
Steven Perry was hospitalized on Aug. 12 due to a severe central nervous system disease and died on Aug. 19, officials said.
In Massachusetts, public health officials on Thursday confirmed a second human case of Eastern Equine Encephalitis, or EEE, this year as well as a second confirmed case in a horse.
Ten communities in Plymouth and Worcester counties were raised to high or critical risk for EEE after state health officials announced in mid-August that a man in his 80s had caught the disease, the first human case found in Massachusetts since 2020. In Oxford, town officials approved a recent curfew due to EEE risk.
In Plymouth, town officials said that all public parks and fields will be closed daily from dusk until dawn in response to the town’s high-risk status.
Massachusetts will start mosquito spraying amid critical risk for rare but deadly virus
Most people infected with West Nile virus do not develop any symptoms, according to the CDC. About 1 in 5 people who are infected develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea, or rash. Most people with febrile illness due to West Nile virus recover completely, but fatigue and weakness can last for weeks or months.
About 1 in 150 people who are infected develop a severe illness affecting the central nervous system such as encephalitis, or inflammation of the brain, or meningitis, or inflammation of the membranes that surround the brain and spinal cord.
Local and state officials shared the following tips to help prevent mosquito bites and the transmission of West Nile Virus and EEE:
Avoid mosquito bites and 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 the evening, after 6 p.m. or early morning. Otherwise, take extra care to use repellent and protective clothing. Mosquitoes can be active during daylight hours when the temperatures are cool.
Clothing can help reduce mosquito bites. Although it may be difficult to do when it is hot, wearing long sleeves, long pants and socks when outdoors will help keep mosquitoes away from your skin.
Apply insect repellent when you go outdoors. Use a repellent with DEET (N, N-diethyl-m-toluamide), permethrin, picaridin (KBR 3023) or oil of lemon eucalyptus [p-methane 3, 8-diol (PMD)] according to the instructions on the product label. DEET products should not be used on infants younger than 2 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 younger than 3 years of age.
Mosquito-proof your Home and drain standing water. Mosquitoes lay their eggs in standing water. Limit the number of places around your home for mosquitoes to breed by either draining or getting rid of items that hold water. Check rain gutters and drains. Empty any unused flowerpots and wading pools, and change water in birdbaths frequently.
Install or repair screens. Some mosquitoes like to come indoors. Keep them outside by having tightly fitted 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 West Nile Virus 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 West Nile Virus- and EEE-positive results can be found at this website 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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