State Health Officials Announce Eighth Human Case of West Nile Virus in Massachusetts

The Massachusetts Department of Public Health (DPH) today announced the eighth human case of West Nile virus (WNV) in the state this year. The individual is a male in his 50s who was exposed to WNV in Middlesex County.

Twenty-seven communities in Essex, Middlesex, Norfolk, and Suffolk counties are at high risk and 71 communities are at moderate risk. There are no additional risk level changes associated with this new case.

“The risk from WNV is starting to decline but some risk will remain until the first hard frost,” said Acting Public Health Commissioner Margret Cooke. “Although people over the age of 50 are at greater risk from West Nile virus, all ages can be affected. People should remember to take steps to prevent mosquito bites anytime they are outdoors.”

In 2020, there were 11 human cases of WNV infection identified in Massachusetts. 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.

People have an important role to play in protecting themselves and their loved ones from illnesses caused by mosquitoes.

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-menthane 3, 8-diol (PMD)], or IR3535 according to 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 mosquitoes. 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 mosquitoes away from your skin.

Mosquito-Proof Your Home
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 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 mosquitoes 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 should be flushed out 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 Eastern Equine Encephalitis (EEE). If an animal is diagnosed with WNV or EEE, owners are required to report to the Massachusetts Department of Agricultural Resources’ (MDAR) Division of Animal Health by calling 617-626-1795 and to the 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/MosquitoesandTicks or by calling the DPH Epidemiology Program at 617-983-6800.