Public health officials report first Idaho West Nile virus meningitis case of 2026

Idaho's first reported case of human West Nile virus (WNV) meningitis this year was identified in a Canyon County resident over the age of 65. This person had been hospitalized for the illness but is recovering at home.

WNV is spread by the bite of an infected mosquito and can lead to severe disease in some people. West Nile neuroinvasive disease is a rare but serious complication of West Nile virus infection that occurs when the virus affects the brain or spinal cord, causing conditions such as meningitis, encephalitis (swelling of the brain), or paralysis.

"If you or someone you know takes medications that suppress your immune system, such as treatments for cancer, autoimmune diseases, or organ transplants, your risk of developing severe West Nile virus illness after a mosquito bite, including death may be up to 40% higher," said Southwest District Health Epidemiologist Lekshmi Rita Venugopal. "With West Nile virus detected in mosquitoes in Southwest Idaho again this summer, it's especially important for people with weakened immune systems to avoid mosquito bites."

Idaho State Epidemiologist Dr. Christine Hahn said public health officials strongly encourage Idahoans to protect themselves and their families from mosquito bites.

"The report of the first severe West Nile virus disease of the season in an Idaho resident is a good reminder for all of us to take protective measures against mosquito bites," she said. "This includes wearing insect repellent and protective clothing in addition to reducing standing water around gardens and homes where mosquitoes can lay eggs."

Symptoms of WNV infection often include fever, headache, body aches, nausea, and sometimes swollen lymph glands or a skin rash. WNV infection can result in severe illness, especially in people 50 years or older, leading to hospitalization and even death. Talk to your healthcare provider about testing for WNV to confirm your illness.

There are no licensed vaccines or medicines to prevent WNV disease in people. To protect against WNV infection, people should avoid mosquitoes, particularly between dusk and dawn when the mosquitoes that spread WNV are most active. In addition, everyone should:

• Wear long, loose-fitting shirts and pants when outdoors and apply DEET or other EPA-approved insect repellent to exposed skin and clothing. Carefully follow instructions on the product label, especially for children.
• Keep mosquitoes outside the home by using screens on windows and doors or air conditioning, if available. Repair or replace damaged screens.
• Reduce standing water on property. Check and drain toys, flowerpots, buckets, kiddie pools, and other items left outdoors that can hold water.
• Change bird baths, static decorative ponds, kiddie pools, and animal water tanks weekly to reduce suitable mosquito habitats.
• Consider larvicides for bodies of water that will not be used for drinking and cannot be covered or dumped out.

WNV activity in mosquitoes has been detected in seven Idaho counties this year by participating mosquito abatement districts.

For more information, visit the following resources:

• https://westnile.idaho.gov
• www.cdc.gov/west-nile-virus/index.html
• www.epa.gov/insect-repellents
• www.cdc.gov/mosquitoes/mosquito-control/mosquito-control-at-home.html
• www.cdc.gov/han/php/notices/han00532.html

The Idaho Department of Health and Welfare is dedicated to strengthening the health, safety, and independence of Idahoans. Learn more at healthandwelfare.idaho.gov.

Southwest District Health is one of seven public health districts throughout Idaho established to protect and promote the health and wellness of those who live, work, and play in our region. We proudly serve Adams, Canyon, Gem, Owyhee, Payette and Washington Counties. We work in partnership with our community to identify health needs, design solutions, and implement services that encourage behaviors contributing to healthier, longer lives. Learn more at www.swdh.org.