The Associated Press

CLEVELAND - An Ohio county with one of the highest human infection rates in the nation for West Nile virus is testing volunteers to try to explain why some communities were hit so hard.

Teams from health departments and hospitals are visiting homes in Cuyahoga County through Dec. 15, asking residents to answer some questions and to give blood samples for testing.

The Ohio Health Department reports the state had 430 likely or confirmed cases of West Nile in humans this summer and fall, including 215 in Cuyahoga.

The virus caused 22 deaths in the state, nine of them in Cuyahoga, the department said.

The county with the next highest human infection rate was Hamilton in southwest Ohio with 28 cases.

State health officials have said they are not sure why Cuyahoga had so many cases.

The Ohio Health Department suspects the virus moved into the state along Lake Erie's shore.

Most cases counted were ones that required medical attention. But most people infected show no symptoms or develop a mild flulike illness.

Because antibodies that fight the virus remain in the blood for months, county officials hope test results will help estimate the true infection rate as they plan ways to avoid another bad outbreak next year.

County officials hope to collect at least 1,000 samples with the $400,000 study.

The survey is confidential, and donors will receive their blood test results.