First Human Cases of West Nile Virus Confirmed in Massachusetts

The Massachusetts Department of Public Health (DPH) announced that two positive human cases of West Nile virus (WNV) have been confirmed in the state. Somerville and surrounding communities are considered to be at moderate risk for WNV. Somerville residents should continue to take precautions to protect themselves against mosquito bites and mosquito-borne diseases, including WNV and Eastern Equine Encephalitis (EEE). 

“This is the first time that West Nile virus infection has been identified in Massachusetts residents this year,” said Massachusetts Public Health Commissioner Robert Goldstein, MD, PhD. “August and September are the months when most people are exposed to West Nile virus in Massachusetts. Populations of mosquitoes that can carry and spread this virus are fairly large this year and we have seen recent increases in the number of WNV-positive mosquito samples from multiple parts of the Commonwealth.”

While WNV and EEE can infect people of all ages, people over 50 are at higher risk for severe WNV, and people under 15 are particularly vulnerable to EEE. WNV and EEE symptoms tend to include fever and flu-like illness. 

DPH recommends the following precautions:

Avoid Mosquito Bites 

• Apply insect repellent when you go 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 2 months old and should be used in concentrations of 30% or less on older children. Oil of lemon eucalyptus should not be used on children under 3 years old. Permethrin products are intended for use on items such as clothing, shoes, bed nets, and camping gear and should not be applied to skin.  
• Clothing can help reduce mosquito bites. Although it may be difficult to do when it’s hot, wearing long sleeves, long pants, and socks outdoors will help keep mosquitoes away from your skin. 
• Be aware of peak mosquito hours. The hours from dusk to dawn are peak biting times for many mosquitoes. When risk increases, consider rescheduling outdoor activities that occur during the evening or early morning. If you are outdoors and notice mosquitoes around you, take steps to avoid being bitten by moving indoors, covering up, and/or wearing repellant. 

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 draining or discarding items holding water. Check rain gutters and drains. Empty any unused flowerpots and wading pools, and frequently change the water in birdbaths. 
• Install or repair screens. Keep mosquitoes outside by having tightly fitting screens on your windows and doors. 

Protect Your Animals 

• Animal owners should reduce potential mosquito breeding sites 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 to reduce mosquitoes near paddock areas.  
• Owners should also speak with their veterinarian about mosquito repellents approved for animal use and vaccinations to prevent WNV and EEE.  
• If an animal is suspected of having WNV 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. 

For more information, go to mass.gov/dph/mosquito or call the Massachusetts DPH Epidemiology Program at 617-983-6800.