Oklahoma County has the highest concentration of West Nile virus infections in the Oklahoma City metro, and Carter County has the highest concentration statewide. But the state epidemiologist says there are too many factors at play to know why some areas are worse than others.
Weather, vegetation, bird populations and human population density are among factors that influence where West Nile will be most widespread. The number of factors is high enough, and variance within those factors broad enough, that West Nile can spread unpredictably.
“It causes challenges in predicting from one year to the next if this is going to be a more severe season than we expected, and also where to target our surveillance and our mosquito control efforts,” said Kristy Bradley, the state Health Department epidemiologist.
The Health Department had reported 150 confirmed cases of human West Nile infection in Oklahoma as of Tuesday, which represents about four infections per 100,000 state residents. Eighty-seven people have been hospitalized, and eight have died.
Carter County has the highest infection rate in the state by far, no matter how large the sample size, according to the health department. Fifteen residents of Carter County, which features Ardmore as the largest city, have been infected by the virus, representing nearly 32 infections per 100,000 county residents.
Oklahoma County has 50 confirmed cases, which along with Pottawatomie County's five infections represents about seven per 100,000 residents. The rate drops to about five infections per 100,000 residents in Logan County and about two per 100,000 residents in Cleveland and Canadian counties.
Tulsa County's infection rate of about five people per 100,000 residents is only slightly higher than the state average. Most other counties with high rates of infections have a comparatively small sample size, with the exception of Pittsburg County's 10 infections and a rate of about 22 cases per 100,000 residents.
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