The first human case of West Nile virus in Idaho was confirmed in a Blaine County woman in south-central area of the state. The woman, in her 20s, is recovering from West Nile fever and did not require hospitalization.


Culex mosquito
Culex quinquefasciatus

Along with the human infection in Blaine County, eight additional Idaho counties have reported West Nile-positive mosquitoes during routine surveillance beginning in early June. Abatement districts and public health officials are concerned that hot weather and standing water from recent rains could contribute to increased mosquito populations and risks of West Nile infections.

“We are hearing of heavy mosquito populations in a number of areas in the state so people should be taking precautions to fight the bite and protect themselves and their families,” says Dr. Leslie Tengelsen, deputy state epidemiologist. “This is a good warning for everyone to aggressively take protective measures, such as wearing repellent and reducing mosquito breeding habitat around our homes.”

West Nile virus is usually contracted from the bite of an infected mosquito; it is not spread from person-to-person through casual contact. Symptoms of infection often include fever, headache, body aches, nausea, and sometimes swollen lymph glands or a skin rash. In some cases the virus can cause severe illness, especially in people older than 50.

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

  • Apply DEET or other EPA-approved insect repellent to exposed skin and clothing. Carefully follow instructions on the product label, especially for children.
  • Cover up exposed skin when outdoors.
  • Insect-proof your home by repairing or replacing screens.
  • Reduce standing water on your property. Check and drain toys, trays or pots which may hold water. Change the water in bird baths and static decorative ponds weekly as they may provide a suitable mosquito breeding habitat.

West Nile virus does not usually affect domestic animals, 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 vaccinate their horses annually.

Last year, 40 people in Idaho were reported with West Nile virus infections, which contributed to two deaths. Sixteen of Idaho’s 44 counties reported West Nile activity during 2013. In 2006, Idaho led the nation in West Nile illnesses with almost 1,000 infections and 23 deaths.