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NH DHHS Identifies Season’s First Positive Test for West Nile Virus in Mosquito Batch in Salem
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Issued by Bureau of Infectious Disease Control
Publish Date:
August 19, 2021

Concord, NH – The New Hampshire Department of Health and Human Services (DHHS) has identified the first batch of mosquitoes in 2021 to test positive for West Nile Virus (WNV). The batch was collected in the town of Salem on August 3, 2021. DHHS is working with the town of Salem to notify Salem residents and those in the surrounding towns of the positive WNV test. This recent finding will elevate Salem’s risk for arboviral illness from baseline (no detected viral activity) to low Adobe Acrobat Reader Symbol.

"Even though this is the first batch of mosquitos to test positive for West Nile Virus this year, we know that the risk of West Nile Virus infection and other mosquito transmitted diseases is present throughout New Hampshire,” said NH State Epidemiologist Dr. Benjamin Chan. "Until there is a statewide mosquito-killing frost, it remains important for everybody to take steps to prevent mosquito bites, including wearing long sleeves, using an effective mosquito repellant on exposed skin, and avoiding outdoor activities at dawn and dusk when mosquitos are most active."

WNV is one of three arboviruses transmitted from the bite of infected mosquitoes in New Hampshire. The other viruses are Eastern equine encephalitis and Jamestown Canyon virus. WNV was first identified in New Hampshire in August of 2000. Symptoms usually appear within a week after being bitten. Symptoms can include flu-like illness including fever, muscle aches, headaches, and fatigue. Many people may not develop any symptoms, or only develop very mild symptoms. A very small percentage of individuals infected with WNV can go on to develop more serious central nervous system disease, including meningitis or encephalitis. If you or someone you know is experiencing flu-like symptoms, including fever and headache, contact your local medical provider.

Prevention guidelines for WNV and other arboviruses can be found below. Anyone with questions about arboviruses, including WNV, can call the New Hampshire Bureau of Infectious Disease Control at 603-271-4496. Fact Sheets on West Nile virus Adobe Acrobat Reader Symbol and other arboviruses are available on the this website. For more information, please visit the Centers for Disease Control and Prevention website at

Prevention Guidelines for West Nile Virus and
Eastern Equine Encephalitis
NH Department of Health and Human Services, Division of Public Health Services

  • Eliminate habitat and breeding locations.
    • Mosquitoes
      • Mosquitoes lay their eggs in standing water. Remove outdoor items that hold water (old tires, cans, plastic containers, ceramic pots).
      • Drill holes in the bottom of outdoor recycling containers, clean roof gutters and ensure proper drainage.
      • If not in use, empty and/or cover swimming pools, wading pools and hot tubs.
      • Turn over wheelbarrows and change water in birdbaths at least twice weekly.
      • Minimizing areas where hosts for the ticks, such as rodents and deer, can congregate to eat, sleep or feed.
  • Be aware of where mosquitoes and ticks live.
    • Weeds, tall grass, and bushes provide an outdoor home for mosquitoes and ticks, alike.
    • Make sure that doors and windows have tight-fitting screens. Repair or replace all screens in your home that have tears or holes.
    • Resting mosquitoes can often be flushed from indoor resting sites by using sweeping motions under beds, behind bedside tables etc. and once in flight, exterminated prior to sleeping at night.
    • Avoid tick-infested areas. If in tick-infested areas, walk in the center of trails to avoid contact with overgrown grass, brush, and leaf litter at trail edges.
  • Protect yourself from bites.
    • When outside, wear protective clothing such as socks, long-sleeved shirts, and long pants (preferably tucked in socks). Light-colored clothing helps you spot ticks.
    • Wear insect repellents, such as one containing 30% or less DEET (N,N-diethyl-methyl-meta-toluamide), Picaridin, para-menthane-diol, IR3535, or 2-undecanone or oil of lemon eucalyptus.
      • Treat clothing with permethrin, ideal for hunters as it is odorless when dry.
    • Vitamin B, ultrasonic devices, incense, and bug zappers have not been shown to be effective in preventing mosquito bites.
    • Shower as soon as possible after spending time outdoors.
    • Check for ticks daily, on you and your pets. Ticks can hide under the armpits, behind the knees, in the hair, and in the groin.
    • Wash and dry clothing after being outdoors. Tumble clothes in a dryer on high heat for 10 minutes to kill ticks on dry clothing. If the clothes are damp, additional time may be needed.
    • Early removal of ticks can reduce the risk of infection. Inspect all body surfaces carefully, and remove attached ticks with tweezers. Monitor your health closely after a tick bite and be alert for symptoms of illness. Contact your physician to discuss testing and treatment.

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New Hampshire Department of Health and Human Services
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