Maine.gov logo
Agency logo

Home → Diseases & Conditions → West Nile Virus (WNV)

West Nile Virus (WNV)

About

West Nile virus (WNV) is a viral illness spread by mosquitoes. It can cause disease in humans, birds, and some other mammals. It occurs throughout the United States, including in Maine. 

West Nile virus spreads through the bite of an infected mosquito. West Nile cases occur sporadically in Maine, usually during the summer and fall when mosquitoes in Maine are most active. 

Anyone can get WNV, but certain people are at higher risk, including: 

  • People who spend a lot of time outdoors, whether for work, hobbies, or recreation.
  • People over 50 years of age.
  • Children under 15 years of age.
  • People who have certain conditions, like cancer, diabetes, high blood pressure, or kidney disease.
  • People who have certain conditions or take medications that weaken the immune system. 

West Nile Virus and Birds

West Nile can infect certain kinds of birds and cause them to die. If you find three or more dead birds at the same time in the same place, report these die offs to Maine Department of Inland Fisheries and Wildlife. 

Symptoms

Most people infected with West Nile virus do not develop any symptoms. However, symptoms may develop. This usually occurs 3 to 15 days after being bitten by an infected mosquito. Symptoms include: 

  • Fever and chills
  • Weakness
  • Headache
  • Body and muscle pain

More severe signs and symptoms may develop, though these are rare. While severe illness can occur at any age, people over 60 years of age or people with certain medical conditions are at greater risk. Serious symptoms include: 

  • Inflammation of the brain (encephalitis)
  • Confusion
  • Neck stiffness
  • Severe headache
  • Coma

Treatment

Talk to a health care provider if you have any of these symptoms. There is no specific treatment for WNV. Severe WNV illness usually requires supportive treatment in the hospital. 

Prevention

Maine Mosquito Meter

Check out the Maine Mosquito Meter! Use this risk meter to understand what prevention steps you should take to prevent mosquito-borne disease throughout the mosquito season. 

Prevent Mosquito Bites

The best way to prevent mosquito-borne disease is to prevent mosquito bites in the first place. Take these simple steps every day to prevent mosquito bites: 

  • Wear clothes that cover your arms and legs, like long sleeves and pants.
  • Use an EPA-approved bug spray. This includes products that contain DEET, picaridin, IR3535, and oil of lemon eucalyptus.
  • Treat clothing with permethrin. Never use this directly on your skin.
  • Avoid outdoor activities at dusk and dawn, when mosquitoes are most active. 

Protect Your Yard from Mosquitoes

You can make your yard a mosquito-safe zone: 

  • Discard man-made containers around your yard that can hold water. If you cannot remove them, consider drilling holes in them to keep them from holding water.
  • Empty sources of standing water around your home, including in man-made containers.
  • Put plant pots, yard toys, and other containers that hold water away or store upside-down to keep them from filling with water.
  • Change the water at least once every week in containers that have to hold water, like birdbaths and pet water bowls. This makes sure that mosquito larvae (baby mosquitoes) cannot grow into adults.
  • Check window and door screens for holes that mosquitoes can fly through and fix them. 

Data and Publications

Arboviral Surveillance

Maine CDC tests for Eastern Equine Encephalitis virus (EEE), Jamestown Canyon virus (JCV), and West Nile virus (WNV) in humans, animals, and mosquitoes. Find the Arboviral Surveillance Reports posted weekly from July through September. This data helps Maine CDC understand where mosquito-borne diseases might be in Maine. This helps to guide prevention efforts to prevent humans and domestic animals from getting sick. 

Surveillance Reports

West Nile Resources