The easiest and best way to avoid WNV is to prevent mosquito bites.

Elevated risk from WNV in 13 communities; some risk persists everywhere

The Massachusetts Department of Public Health (DPH) today announced the fourth and fifth human cases of West Nile virus (WNV) in the state this year. One resident, in Norfolk County, is in her 40s and developed a milder form of the disease. She was never hospitalized. The other resident, from Middlesex County, is in his 80’s and was hospitalized but has been discharged. Both individuals were diagnosed with WNV by testing completed today by the Massachusetts State Public Health Laboratory.

The identification of multiple human cases from a defined geographic area indicates that the risk to people from WNV has increased from moderate to high in the area.

The communities now considered to be at high risk for WNV for the remainder of the season are:

Arlington, Belmont, Boston, Brookline, Cambridge, Chelsea, Everett, Medford, Newton, Revere, Somerville, Watertown and Winthrop.

“Despite the anticipated cooler temperatures,” said DPH State Public Health Veterinarian Dr. Catherine Brown, “the species of mosquitoes that carry WNV will continue to be quite active for at least the next several weeks. We are urging people, especially people that are older or whose immune systems are compromised, to be especially vigilant about avoiding mosquito bites.”

In 2015, there were ten human cases of WNV infection identified in Massachusetts, eight of which were confirmed in the month of September. 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. When present, WNV symptoms tend to include fever and flu-like illness. In rare cases, more severe illness can occur.

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 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 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 DAR, Division of Animal Health by calling 617-626-1795 and to the Department of Public Health (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 at www.mass.gov/dph/mosquitoor by calling the DPH Epidemiology Program at 617-983-6800. Residents of Boston can call the Boston Public Health Commission at 617-534-5611 for more information.