DES MOINES, Iowa —

In late August, a doctor in Marshalltown saw back-to-back patients with a respiratory illness.

The doctor suspected it was more than a sinus infection.

Those cases led to the state's largest legionella outbreak, according to Dr. Matthew Donahue, the state's epidemiologist for the Iowa Department of Health and Human Services.

An official outbreak was announced by HHS on Sept. 4.

"Once we started looking at where everybody lived, that's where this pattern emerged," Donahue said.

The outbreak lasted until Oct. 23, when nearly a month passed with no new cases. County and state officials hunted for a cause while the final tally came to 74 cases, including 36 hospitalizations and two deaths.

The source remains elusive, despite a focus on cooling towers in a specific are

See Full Page