The first positive human case of mosquito-borne West Nile virus (WNV) in Idaho this season has been confirmed in Canyon County by Southwest District Health officials in a male in his 50s who resides in Canyon County but may have been exposed in Adams County. Both counties have previously reported WNV-positive pools of mosquitoes this season.

The individual reported mosquito bites before the onset of his illness in mid-July, according to public health officials. His symptoms included high fever, severe headaches, rash, body aches, vomiting and diarrhea. 

WNV is a potentially serious illness that is usually spread to animals and humans through the bite of an infected mosquito. It does not spread from person-to-person. Most people infected with the virus do not show symptoms, although more severe symptoms may occur. People with symptoms may experience fever, headaches, body aches, fatigue, nausea, vomiting, and sometimes swollen lymph glands or a skin rash typically occurring 2 to 14 days after the bite of an infected mosquito.

“About one in 150 people infected with WNV develop severe illness such as encephalitis (inflammation of the brain), or meningitis (inflammation of the linings of the brain and spinal cord),” said Jami Delmore, Environmental Health Supervisor for Southwest District Health in Caldwell. “These more severe infections are marked by a rapid onset of a high fever, headache, neck stiffness, body aches, disorientation, and tremors,” she said.

The Idaho Department of Health and Welfare tracks WNV each season, documenting locations of infected mosquitoes, horses and birds, and symptomatic human cases. You can see the latest data on this map. Currently, West Nile virus activity is centered in the southwestern portion of the state, but historically WNV-positive pools of mosquitoes have been found in each of Idaho’s 44 counties.

See below for advice on how to “Fight the Bite” this season to reduce your risk of West Nile virus, or visit www.westnile.idaho.gov

Media: For information on the Canyon County human WNV case, contact Katrina Williams at Southwest District Health, (208) 455-5317.

Original Post from June 13, 2018:

Mosquitoes infected with West Nile virus (WNV) were detected in Canyon County on June 12, 2018, prompting public health officials to remind people to take precautions to “Fight the Bite.” The positive mosquitoes, which are the first detected in the state this year, were collected by the Canyon County Mosquito Abatement District.

Last year, 13 counties across the state reported finding WNV-positive mosquito pools. Additionally, WNV infection was reported in 25 people, seven horses, three birds, and one llama. This first detection in 2018 occurred in western Idaho, an area where positive mosquitoes have been found almost every year since WNV was introduced in 2004.

WNV is usually contracted from the bite of an infected mosquito; it is not spread from person-to-person through casual contact. Symptoms often include fever, headache, body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash. In some cases, the virus can cause severe illness, especially in people over the age of 50, and may require hospitalization – and, on rare occasion, lead to death.

“Disease-carrying mosquitoes will be around now until a killing frost so it is critical that you protect yourselves and your family members from their bite,” says Dr. Leslie Tengelsen, from the Division of Public Health. “Finding positive mosquitoes in one part of the state is an indication that conditions are right for virus transmission so you should avoid mosquito bites even if tests have not yet confirmed the virus in your local mosquitoes.”

To reduce the likelihood of infection, avoid mosquitoes, particularly between dusk and dawn when they are most active. In addition, you should:

• Cover up exposed skin when outdoors and apply DEET or other U.S. Environmental Protection Agency-approved insect repellent to exposed skin and clothing. DEET may be used on adults, children, and infants older than 2 months of age. Carefully follow instructions on the product label, especially for children. When used as directed, EPA-registered insect repellents are proven safe and effective, even for pregnant or breastfeeding women.
• Insect-proof your home by repairing or replacing screens.
• Reduce standing water on your property; check and drain toys, trays, or pots outdoors that may hold water and harbor mosquito eggs.
• Change bird baths and static decorative ponds weekly as they may also provide a suitable mosquito habitat.

WNV does not usually affect domestic animals such as dogs and cats, but it can cause severe illness in horses and certain species of birds. Although there is no vaccine available for people, there are several vaccines available for horses. People are advised to keep their horses vaccinated annually.

For the latest information, visit www.westnile.idaho.gov.

Canyon County Mosquito Abatement District: http://canyoncountymosquito.com/