Date: September 25, 2023


Public Information Office
(603) 271-9389 |

NH DHHS Announces Mosquito- and Tick-Transmitted Infections in the State

Residents and Visitors Urged to Take Steps to Prevent Bites

Concord, NH - The New Hampshire Department of Health and Human Services (DHHS), Division of Public Health Services (DPHS) is announcing the State’s first human case of Jamestown Canyon Virus (JCV) infection in an adult from Hillsborough County. In addition, DPHS is reporting two cases of Powassan Virus (POWV), one in an adult in Rockingham County and one in a child from Carroll County. Risk for both mosquito- and tick-transmitted infections remains high, and the Department urges residents and visitors to continue to take steps to prevent mosquito and tick bites.  

“Mosquitoes will be with us until the first hard frost, and ticks remain active as long as there is no snow cover and temperatures remain above freezing,” said Ryan Tannian, Chief of the DPHS Bureau of Infectious Disease Control. “Preventing the bites that cause illnesses transmitted by mosquitoes and ticks is a key factor in reducing the risk for illness.”

This summer, 14 batches of mosquitos around the state tested positive for JCV, and New Hampshire has reported a total of 13 human cases of JCV since 2018. New Hampshire has identified a total of 8 cases of POWV since 2013, when the disease was first detected in humans in New Hampshire. 

JCV is transmitted by the bite of an infected mosquito and symptoms of infection may include flu-like illness, fever, muscle aches, headaches, and fatigue. Individuals with JCV can progress to more serious central nervous system diseases, including meningitis or encephalitis. Other infections transmitted by mosquitos include Eastern Equine Encephalitis (EEE) and West Nile Virus (WNV) which also present with symptoms similar to JCV.

POWV is transmitted through the bite of the blacklegged tick. An infected tick only needs to be attached to a person for 15 minutes to transmit POWV. This is the same tick that transmits Lyme Disease, Anaplasmosis, and Babesiosis. Early symptoms can include fever, muscle aches, headaches, and fatigue. More serious central nervous system disease, including meningitis or encephalitis can occur.

There are no vaccines or anti-virus medications to treat JCV or Powassan virus infections. The best way to stay healthy and prevent illness from these and other tick- and mosquito-transmitted infections is to prevent tick and mosquito bites.  

For more information on national data on JCV and POWV, visit and

Anyone with questions about vector-borne illnesses can call the DPHS Bureau of Infectious Disease Control at (603) 271-4496 from 8:00 AM to 4:30 PM, Monday through Friday. More information can also be found at and 



Prevention Guidelines for Mosquito and Tick Diseases

NH Department of Health and Human Services, Division of Public Health Services

1. 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.
  • Ticks
    • Minimizing areas where hosts for the ticks, such as rodents and deer, can congregate to eat, sleep or feed.

2. Be aware of where mosquitoes and ticks live.

  • Weeds, tall grass, and bushes provide an outdoor home for mosquitoes and ticks alike.

3. Protect yourself from bites.

  • 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.
  • 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.
  • Consider avoiding outdoor activities in the early morning and evening, when mosquitoes are most likely to be biting. 
  • 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.
  • 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, which 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. 

For more information on mosquito-borne diseases, visit the Mosquito-borne Illnesses page.