State public health officials announce four new human cases of West Nile Virus in Massachusetts Peak risk for WNV infection continues through September

The following was submitted by Director of Public Health Julia Junghanns, updated September 18:

Today we were advised by the MDPH that a mosquito collected on September 10th in Wayland tested positive for West Nile Virus. The mosquito was collected in the Southeast area of Wayland. At this time our risk level has not changed as it was upgraded last week to “moderate” due to mosquito-borne disease activity in adjacent communities. Although mosquito populations are currently low due to cooler weather, our messaging has not changed and we continue to inform the public of measures that individuals can take to protect themselves and their loved ones from mosquito-borne illness. The risk for mosquito-borne illness can continue into the fall.

The following was submitted by Director of Public Health Julia Junghanns on September 11

BOSTON (September 10, 2020) – The Massachusetts Department of Public Health (DPH) announced four additional human cases of West Nile virus (WNV) in the state this year. This brings the total number of WNV cases to seven. Three of the four cases are male – one in his 40s, one in this 60s, and one in his 80s. All were exposed to WNV in Middlesex County. WNV was also diagnosed in a female under the age of 19 with exposure in Bristol County.

As a result of information obtained during case investigations on where the four individuals were exposed to the virus, the communities of Cambridge, Newton, Somerville, and Watertown in Middlesex County were elevated to high risk for WNV. Concord, Lexington, Lincoln, Sudbury, Waltham, Wayland, Weston, and Winchester, all in Middlesex County, were elevated to moderate risk. The municipalities of Dighton, Fall River, and Swansea in Bristol County were also elevated to moderate risk.

Most WNV virus activity this year has been focused in an area around Boston and includes parts of Norfolk, Middlesex, and Essex counties.

There had been three cases of WNV already reported in Massachusetts this year. In 2019, there were five human cases of WNV infection. WNV is usually transmitted to humans through the bite of an infected mosquito. While WNV can infect people of all ages, people over the age of 50 are at higher risk for severe disease. Most people infected with WNV will have no symptoms. Updated case information is available at

When present, WNV symptoms tend to include fever and flu-like illness. In rare cases, more severe illness can occur.

NOTE:  in preparation for Wayland Town Meeting, by request, the East Middlesex Mosquito Control Project has sprayed for mosquitoes, to reduce populations, using a perimeter spray (Mavrik Perimeter EPA # 2724-478 applied using back packs).  The area sprayed is the perimeter of the High School athletic field where town meeting will take place.  Please note that the actual athletic field is NOT sprayed fields can be used for activities with no interruption.  All protocols have been followed and signage has been posted.

People have an important role to play in protecting themselves and their loved ones from illnesses caused by mosquitoes. DPH recommends the following precautions:

  • Avoid Mosquito Bites
  • Apply Insect Repellent when Outdoors. Use a repellent with DEET (N, N-diethyl-m-toluamide), permethrin, picaridin (KBR 3023), oil of lemon eucalyptus [p-methane 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% 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 mosquitos. Consider rescheduling outdoor activities that occur during the evening or early morning.
  • Clothing Can Help Reduce Mosquito Bites. Wear long-sleeves, long pants, and socks when outdoors to help keep mosquitos away from your skin.
  • Mosquito-Proof Your Home
  • Drain Standing Water. Mosquitos lay their eggs in standing water. Limit the number of places around your home for mosquitos to breed by either draining or discarding items that hold water. Check rain gutters and drains. Empty any unused flowerpots and wading pools, and change the water in birdbaths frequently.
  • Install or Repair Screens. Keep mosquitos outside by having tightly-fitting screens on all of your 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 mosquitos near paddock areas. Horse owners should keep horses in indoor stalls at night to reduce their risk of exposure to mosquitos. 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 diagnosed with WNV or EEE, owners are required to report to the Department of Agricultural Resources, Division of Animal Health, by calling 617-626-1795 and  DPH by calling 617-983-6800.

More information, including all WNV and EEE positive results, can be found on the Arbovirus Surveillance Information web page or by calling the DPH Epidemiology Program at 617-983-6800.

Catch basins have been treated for mosquitoes

The catch basins in town have been treated with Altosid XR Ingot Slim Briquets, slow release larvicide control lasting up to 150 days. This product has (S) methoprene which interrupts normal development of mosquito larvae.  The product is supplied by the Wayland Board of Health and distributed by the East Middlesex Mosquito Control Project.  This treatment is done every year to control mosquito larvae to reduce mosquito-borne illness.  Altosid is a larvicide in a briquet form that disrupts the normal growth pattern of immature mosquitoes in water and prevents them from becoming breeding, biting adults.  This product is a long-term (up to 150 days), cost-effective and environmentally responsible mosquito control larvicide.

The treated catch basins have been marked with a white dot.  The Town of Wayland contracts the services of the East Middlesex Mosquito Control Project for mosquito control including helicopter spraying using BTI larvicide in the spring and catch basin treatments in the early summer.  Our program during mosquito season also includes mosquito trapping, identifying populations and surveillance for diseases and species.  To review the state’s plan for 2020 see below link to MDPH Arbovirus Surveillance plan.

For further information on WNV or EEE, log unto the Massachusetts Department of Public Health web site at:

If residents have any questions about mosquitoes or how to control them: the East Middlesex Mosquito Control Project can be reached at:

Choosing and using repellents safely:

The National Pesticide Information Center (NPIC) toll free at 1-800-858-7378 or online at  If you can’t go online contact MDPH at (617)983-6800 for a hard copy of the fact sheet.


Julia Junghanns, R.S., C.H.O.

Director of Public Health



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