MARSHALLTOWN, Iowa —

Searching for a source of Legionnaires' disease sounds a little like hide and seek.

State health officials are trying to figure out what's causing more cases of the illness in Marshall County, where there have been 30 confirmed cases, including one death .

The disease spreads by inhaling bacteria-contaminated water droplets.

At this time, a source or sources have not been identified.

"There's a lot of different possibilities here at this point, and I hope the investigation narrows it down," said Caitlin Proctor, assistant professor at Purdue University.

The nature of Legionella, the bacteria that cause the illness, can make it tricky to track down. Legionella seems to prefer late summer and early fall, when temperatures are warmer. It can also be fickle in its

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