Idaho’s first human case of West Nile virus infection this year has been confirmed in a Washington County woman in southwest Idaho. The woman, over the age of 50, is recovering from West Nile fever and did not require hospitalization.

Nine Idaho counties in Idaho have reported West Nile virus-positive mosquitoes during routine surveillance which began in mid-June. In addition, a horse, also from Washington County, tested positive for the virus.

Mosquito abatement districts and public health officials are concerned the unseasonably hot weather in late June followed by instances of heavy rains has resulted in increased mosquito populations and an elevated risk of West Nile infection. 

“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, state public health veterinarian. “This is a good warning for all of us to take protective measures, including wearing insect repellent and reducing mosquito habitat around our homes.”

Last year, 19 human cases of West Nile infection were reported from 15 counties, with no deaths. However, in 2006 Idaho led the nation for West Nile virus illnesses with almost 1,000 infections that contributed to 23 deaths. Last year was the first year the Panhandle of the state detected West Nile virus, with a mosquito pool from Boundary County testing positive.

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:

• Cover up exposed skin 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.
• Insect-proof your home by repairing or replacing screens.
• Reduce standing water on your property; check and drain toys, trays or pots outdoors which may hold water.
• Change bird baths and static decorative ponds weekly as they may provide a suitable mosquito 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.

For more information, please visit www.westnile.idaho.gov.