For Immediate Release - August 27, 2015

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

Residents urged to take precautions to avoid mosquito bites

BOSTON — The Massachusetts Department of Public Health (DPH) today announced the first human case of West Nile virus (WNV) in the state this year. The patient is a resident of Middlesex County in his 40’s who was diagnosed with WNV by testing completed today by the State Public Health Laboratory. The patient remains hospitalized.

DPH is conducting an epidemiological investigation to determine where the man was most likely exposed to infected mosquitoes. Assessment of WNV risk areas will depend on the findings of this investigation.

“Massachusetts is in peak season for possible West Nile virus infection for human infections,” said DPH State Public Health Veterinarian Dr. Catherine Brown. “We need to continue to take steps to protect ourselves against mosquito bites: use insect repellant, cover up, and reduce outdoor activities at dusk and after nightfall when mosquitoes are at their most active.”

In 2014, there were six 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-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 mosquitoes. Consider rescheduling outdoor activities that occur during evening or early morning.
  • Clothing Can Help Reduce Mosquito Bites
    Wearing long-sleeves, long pants and socks when outdoors will 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 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 provide excellent mosquito breeding habitats and should be flushed out at least once a week during the summer months 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 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 or by calling the DPH Epidemiology Program at 617-983-6800.

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