West Nile Virus (WNV) in Somerville

  • Updates & Alerts

  • About Mosquito-Borne Illness

BOSTON (August 27, 2018) - The Massachusetts Department of Public Health (DPH) today announced the fourth human case of West Nile virus (WNV) in the state this year. The person is a woman in her 50s from Middlesex County who was never hospitalized for her illness. Three other cases were reported on Friday.

Investigations conducted by state public health officials indicate that at least two of the four cases were exposed in the greater Boston area leading them to raise the risk level from moderate to high for 11 communities in the area. Those communities are Arlington, Boston, Belmont, Brookline, Cambridge, Chelsea, Everett, Medford, Newton, Somerville, and Watertown.

“Several individuals from the same area have developed West Nile virus,” said Public Health Commissioner Monica Bharel, MD, MPH. “That means that there is an increased risk in this specific area and that additional people could become infected. We are particularly concerned about people over 50 and those who are immunocompromised as they are the ones most likely to develop WNV disease.”

On August 21, DPH raised the risk level for West Nile virus from low to moderate in every Massachusetts city and town. It was only the second time since WNV was first detected in the Commonwealth in 2000 that public health officials have raised the risk level statewide.

For those 11 communities now at high-risk, DPH recommends that local health officials intensify messaging to raise awareness and promote personal protective behaviors, target outreach to high-risk populations, and increase surveillance for human disease.

People at high risk for severe illness are encouraged to consider avoiding outdoor activity at dusk and dawn. Local boards of health should continue to work directly with their Mosquito Control District to determine appropriate control measures.

“It is extremely important for people to take steps to avoid mosquito bites, including using repellents, wearing clothing to reduce exposed skin, dumping standing water, and moving indoors when you notice mosquitoes biting you,’’ said DPH State Epidemiologist Dr. Catherine Brown.

In 2017, there were 6 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 can take steps to protect 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. 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 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 www.mass.gov/dph/mosquito or by calling the DPH Epidemiology Program at 617-983-6800. 

Late July through September is usually the period of greatest West Nile Virus activity in Massachusetts.

What can you do to prevent mosquito-borne illness?

Avoid Mosquito Bites

  • Apply Insect Repellent when Outdoors:
    Use a repellent with DEEToil of lemon eucalyptus 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.
  • Wear Clothing that will cover your body:
    Wearing long-sleeves, long pants and socks when outdoors will help keep mosquitoes away from your skin, which can prevent mosquito bites. If it’s hot, consider light, loose and breathable clothing that covers you but still allows you to keep cool.  If you’ll be out all day into the evening, bring layers or at least a light throw, so you can cover up after dusk.
  • Wear light-colored clothing and avoid fragrances:
    Mosquitoes see dark colors like blue and black more easily than light colors like tan and white, meaning that dark clothes make you an easy target. So choose light-colored clothing when outdoors. Likewise, fragrances attract mosquitoes. So it’s best to avoid perfumes and scented products when heading outdoors.

Reduce Mosquito Breeding Areas

Mosquitoes lay their eggs in still or stagnant water found in catch basins, roof gutters clogged with leaves, old tires, flower pots, bird baths, swimming pool covers, buckets, cans, barrels, and other places where water can be trapped. You can greatly reduce the city's mosquito population by removing mosquito breeding areas on your property. 

  • Empty, treat, or refresh any outdoor items that hold water:
    • Remove or treat standing water in flower pots, swimming pool covers, buckets, cans, barrels, or persistent puddles. 
    • Do not leave water bowls outside for your animals when they are inside; empty the bowl when not being used.
    • If you have intentional standing water, such as in bird baths or rain barrels, change/use up the water at least every three to five days to prevent mosquito larvae from hatching.
    • Empty and clean kiddie pools daily after use (both for your children’s safety and to prevent mosquitoes).
    • Consider treating standing water that is not eliminated, such as in flower pot saucers, rain barrels, or ditches with wildlife-safe mosquito dunks.
    • Clean rain gutters, leaves in downspouts, and pooled water on flat roofs.  Remember to use caution when you clean out these items.
    • Remove containers that may hold water in places that are hard to see, such as under bushes, porches, decks, or stairs.
    • Repair any leaky outdoor faucets or hoses.

Learn About Mosquito-borne Illness

  • What is Mosquito-borne illness? 
    Mosquito-borne illness is spread by the bite of an infected mosquito. In the Northeastern United States, it is usually caused by viruses such as West Nile Virus or Eastern Equine Encephalitis virus.
  • How common is mosquito-borne illness?
    There is a low risk of infection following a mosquito bite. Most people bitten by infected mosquitoes experience no illness or only mild illness, but a small number of people can develop a more serious disease.
  • How is it spread?
    Mosquito-borne illness is spread to people through the bite of an infected mosquito.
  • When is it spread?
    The time of the year when mosquitoes are most active and most likely to carry disease is between late July and late September, but if the weather remains warm, the risk period can extend as late as November. The time of day when mosquitoes are most active is at night, dusk and dawn, but you can be bitten at any time.
  • Am I at risk?
    People at higher risk for developing serious symptoms from WNV are those over age 50, however Eastern Equine Encephalitis can cause serious illness in any age group.
  • What should I do if I get bitten by a mosquito?
    Mosquito-borne illness is very rare in Somerville. So your risk following a mosquito bite is small. However, you should see your doctor immediately if you develop high fever, confusion, severe headache, stiff neck, or if your eyes become sensitive to light.

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