West Nile claims 12th victim in Oklahoma, health officials say

The state Health Department has reported 173 cases of West Nile virus this year, the highest number of cases the state has seen since the virus entered the U.S. in 1999.

Before this year, 2007 held the record for the highest number of cases, with 107, and the record for deaths, with nine.

West Nile virus is a mosquito-borne illness, not spread through human contact but rather through mosquito bites.

Most people who contract the virus don't develop illness, and if they do, it's usually a mild case.

Symptoms include fever, headache, tiredness and body aches that usually go away in about a week.

People older than 50 are most at risk of developing serious disease from West Nile virus.

This can include a severe infection with intense headache, mental confusion, tremors, muscle paralysis, convulsions or coma, according to the state Health Department.

Public health officials recommend Oklahoma residents continue to use mosquito repellent and wear long sleeves and pants when they go outside.

Also, it's important to remove stagnant water from outside areas, as it can serve as a mosquito breeding ground.