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MARSHALLTOWN — The number of Legionnaires’ disease cases among Marshalltown residents was up to 34 on Tuesday, as public health officials work to identify the source of the outbreak, State Epidemiologist Dr. Matthew Donahue told the Marshall County Board of Supervisors on Wednesday.

Last Thursday, the state reported there had been 21 cases of Legionnaires’ disease diagnosed in Marshalltown, and one death. All of the cases were in people living in the north central part of the city, Iowa Health and Human Services said.

Legionnaires’ disease is caused by Legionella bacteria, which thrive in warm water and typically spread when a person inhales aerosolized water droplets.

Normally, Donahue to

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