As the risk of illnesses spread by mosquitoes increases in the state, the New Hampshire Department of Health and Human Services (DHHS), Division of Public Health Services (DPHS) is providing tips to help residents prevent mosquito bites and mosquito-borne illnesses.

“Mosquito-transmitted diseases can have long-term impacts on people’s health,” said State Epidemiologist Dr. Benjamin Chan. “The risk for diseases like West Nile Virus and Eastern Equine Encephalitis will only increase as the summer progresses and we move into the fall, so everyone should take steps to prevent mosquito bites.”

Mosquitoes become more active during the summer, when the weather is warm. There are three diseases that circulate among mosquitoes in New Hampshire: Jamestown Canyon Virus So far this summer, one mosquito batch from Keene and one mosquito batch from Londonderry have tested positive for JCV, while one mosquito batch from Manchester and one mosquito batch from Nashua have tested positive for WNV.

This year, there have been two New Hampshire residents identified with JCV infections, both adults from Belknap County who were hospitalized for their illness but have since been discharged. There have been no human infections with WNV or EEEV identified yet this season.

While the risk of JCV increases in the spring, the risk of EEEV and WNV increases through the summer and fall as the viruses spread among animal populations in New Hampshire. Though EEEV has not yet been identified in the state in 2024, favorable environmental conditions and EEEV circulation in southern New England states indicate the coming months may be active.

Symptoms of JCV, EEEV, and WNV include flu-like symptoms, such as fever, muscle aches, headaches, and fatigue. In some rare cases, the diseases may progress and infect the nervous system, including the brain and spinal cord.

Granite Staters can take steps to prevent mosquito bites and diseases:

• Protect yourself from bites. When outside, wear protective clothing such as socks, long-sleeved shirts, and long pants. Consider avoiding outdoor activities in the early morning and evening when mosquitoes are most active. Wear insect repellents and treat clothing with permethrin.
• Take precautions in mosquito habitats, including forests, marshes, and tall grasses. Be sure doors and windows have tight-fitting screens without holes to prevent mosquitoes from entering your home.
• Eliminate standing water where mosquitoes lay their eggs. Remove outdoor items that hold water, ensure recycling containers and roof gutters drain properly, empty and/or cover pools that aren’t in use, turn over wheelbarrows, and change water in birdbaths at least twice weekly.

Please call DPHS at 603-271-4496 with any questions about mosquito-borne diseases. For more information about mosquitoes, the illnesses they spread, and how to prevent bites, visit the Mosquito Surveillance and Control page on the DHHS website or the U.S. Centers for Disease Control and Prevention website. View the latest map of mosquito-borne illness risk levels and detections in New Hampshire.