July 12, 2007

Ada County Resident Tests Positive for West Nile Virus

An Ada County man in his 50s has tested positive for West Nile virus, the first laboratory-confirmed human West Nile infection in the Central District Health Department this year. The man is recovering at home.

The man first reported symptoms consistent with West Nile fever on June 21st and was tested by his physician the following day. The diagnosis was confirmed and reported to Central District Health on July 2nd and the investigation completed today. Though laboratory tests indicate the presence of West Nile virus in the man's blood, the investigation was unable to determine whether the man acquired the disease this year or last. In 2006, West Nile virus was confirmed in all but six Idaho counties, infecting a thousand people, 171 of them with more serious neuroinvasive form of the disease. West Nile was at least partially responsible for 23 deaths in Idaho last year.

The man has no recollection of being bitten by mosquitoes this year, so it isn't known where he may have picked up the infection. Surveillance by Ada County Weed & Pest Control so far has not identified any pools of mosquitoes positive for the West Nile virus. However, the neighboring counties of Canyon, Gem and Elmore have all reported finding mosquitoes carrying West Nile virus.

"West Nile virus can cause serious illness, so we urge people to 'Fight the Bite' and take precautions to avoid the mosquitoes that carry the virus," says Nikki Sakata, Program Manager for Communicable Disease Control at CDHD.

West Nile virus is usually spread through the bite of an infected mosquito and is not generally spread from person-to-person or from infected animals to people. About 80 percent of people who are bitten by an infected mosquito will not become sick, but others may experience a mild, flu-like illness that can include headaches, body aches and a fever. Although rare, the virus can lead to serious illness, especially in people over the age of 50.

To protect themselves from mosquito bites people should:

• Insect-proof their homes by repairing or replacing screens;
• Reduce standing water on their property that provides mosquito breeding habitat, such as bird baths and decorative ponds;
• Cover up exposed skin when outdoors;
• Apply insect repellent approved by the EPA to exposed skin and clothing. Follow instructions on the product label, especially for children;
• Avoid mosquitoes when they are most active at dawn and dusk; and
• Report dead birds to your local Fish and Game office.

West Nile virus does not appear to affect most animals including dogs and cats, but can cause severe illness in horses and certain species of birds. Although there is not a vaccine available for people, there are several vaccines for horses. Approximately one-third of horses which contract West Nile virus will die, so horse owners are encouraged to contact their veterinarian about vaccinating their animals. Horse owners who suspect West Nile viral infection in their animal should contact their veterinarian immediately.

Additional information about the West Nile virus is available from the Department of Health and Welfare web site or by calling the West Nile virus hotline 1-877-333-WNV1 (9681) or in the Treasure Valley 334-6500.