Three Human Cases of West Nile Virus Reported in Massachusetts

~ Submitted by the Town of Bedford Health Department

No WNV or EEE positive mosquito pools or human cases in Bedford so far this season.

On September 2, 2021, the Massachusetts Department of Public Health (MDPH) announced two new human cases of West Nile virus (WNV) in the state this year. Both individuals are male, one in his 50s and the other in his 70s, and both were exposed to WNV in Middlesex County. The MDPH previously announced the first human case of WNV identified in Massachusetts, on September 1, 2021. This case was also likely exposed in Middlesex County. There have been no deaths this year associated with WNV.

WNV positive mosquito samples have been identified in Barnstable, Bristol, Essex, Franklin, Hampden, Hampshire, Middlesex, Norfolk, Plymouth, Suffolk, and Worcester Counties. Based on the three human cases in Massachusetts, recent increases in WNV findings in mosquitoes, and weather favorable for mosquito activity, on Thursday the WNV risk level for Bedford was elevated from low to moderate. MDPH Acting Public Health Commissioner Margaret Cooke stated that “we are seeing significant expansion of virus activity in mosquitoes. The risk from West Nile virus will continue until the first hard frost. As we enjoy the unofficial last weekend of summer and then head back to school and work, it is important for people to remember to continue to take steps to avoid mosquito bites.”

Culex mosquitoes are the primary vectors of WNV.  The virus is transmitted to humans by the bite of an infected mosquito. The mosquitoes that carry WNV are common throughout the state and are found in urban as well as more rural areas. While most mosquito species develop in wetlands, Culex mosquitoes prefer to lay their eggs in catchbasins, clogged rain gutters, unused tires, buckets, and other water-holding containers.  While WNV can infect people of all ages, people over the age of fifty (50) are at higher risk for severe infection.

Mosquito Control in Bedford

The Bedford Health Department continues to work with the MDPH and the Eastern Middlesex Mosquito Control Project (EMMCP) to monitor local mosquito populations for mosquito-borne diseases such as WNV and Eastern Equine Encephalitis (EEE). Bedford has a robust mosquito control program that includes an annual helicopter application of biological larvicide to wetland areas in town by EMMCP and each summer the Bedford DPW treats catch basins in town. Additionally, based on acquired surveillance data from five mosquito trap locations in town, the EMMCP will conduct truck-mounted spraying events in Bedford to reduce populations of biting adult mosquitoes. EMMCP will continue to trap and test mosquitos in and around Bedford until the end of September.

EMMCP Truck Mounted Spraying Event Scheduled

East Middlesex Mosquito Control Project is planning to use a truck-mounted aerosol sprayer to reduce mosquito populations. The next spraying event is scheduled for Wednesday, September 8, 2021, between sunset and 11:30 PM, in Bedford neighborhoods west of Springs Road and South Road. Areas also included are roads in the vicinity of Gould Road, Dunster Road, and Francis Kelley Road. If postponed, the area will be rescheduled for Thursday, September 9, 2021. Mosquito spraying announcements may be viewed on the Health Department website at https://www.bedfordma.gov/health-department

Reduce Your Risk for Mosquito Bites

Residents have an important role to play in reducing the risk of WNV and EEE and protecting themselves and their loved ones by taking a few, common-sense precautions. The best protection is prevention.

Mosquito Proof Your Property – Limit the number of places around your home for mosquitoes to develop 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, as some mosquitoes like to come indoors. Keep them outside by having tightly-fitting screens on all open windows and doors.

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 or early morning. Otherwise, take extra care to use repellent and protective clothing.

Clothing Can Help Reduce Mosquito Bites – Although it may be difficult to do when it’s hot, wearing long sleeves, long pants, and socks when outdoors will help keep mosquitoes away from your skin.

Apply Insect Repellent When Outdoors – Use a repellent with DEET (N, N-diethyl-m-toluamide), permethrin, picaridin (KBR 3023), IR3535 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 under two months of age and should be used in concentrations of 30% or less on older children.  Oil of lemon eucalyptus should not be used on children under three years of age.  Permethrin products are intended for use on items such as clothing, shoes, bed nets, and camping gear and should not be applied to the skin.

Protect Your Animals – Speak with your veterinarian about mosquito repellents approved for use in animals and vaccinations to prevent WNV and EEE. Keep animal or pet vaccinations and medications current.

For More Information

Information about mosquito activity in Massachusetts during 2021 can be found on the Mosquito-borne Disease page on the MDPH website at https://www.mass.gov/mosquito-borne-diseases. Facts sheets on WNV, EEE, and other mosquito-related materials are available by contacting the Bedford Health Department at 781-275-6507 or by accessing the Health Department website at https://www.bedfordma.gov/health-department.


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