Flood Fears

"E. coli is a bacteria that could be there," Kapp said. "There's also parasites that could be in the water, such as giardia or cryptosporidosis."

The danger comes when the water "splashes in the eyes, the mouth — your hands are contaminated," she said.

Jennifer Dunlap, a spokeswoman for Indiana Health Department, said it would also take only a small cut or scratch to expose someone to tetanus, an acute, often fatal, disease. Counties have been administering tetanus vaccinations and handing out water testing kits across Indiana and other Midwestern states.

The raging waters also seeped into countless wells, affecting drinking water for thousands of homes and businesses across the region.

The Studio Café in downtown Thiensville, Wis., was forced to shut its doors permanently because its well water tested positive for E. coli.

"They put a boil advisory on us, and since we are a coffee shop, we use a lot of water here," said owner Julie Burton. "For the customers' health, we couldn't justify being open, so we had to close."

Hazardous materials can leach into floodwaters
The problem is most especially acute around facilities where hazardous materials are handled and stored. Like wells and septic tanks, such containers can be breached, spilling their contents into spreading floodwaters.

Hazardous materials crews were called to Black Hawk Park in Cedar Falls, Iowa, on Wednesday after it was discovered that about 15 gallons of 2,4,5-trichlorophenoxyacetic acid — or 245-T, a powerful herbicide commonly found in the defoliant Agent Orange — had spilled in side a maintenance building. The Cedar River had flooded the building, and some of the chemical leaked out.

Vern Fish, director of the Black Hawk County Conservation Board, said the spill was small enough that it was likely to have been diluted to such a point that it was not a threat to people. But "we felt we should err on the side of safety. Rather than just send people in, we had a haz-mat team come in, got a professional evaluation done, and now we've got a better understanding of the situation."

The Environmental Protection Agency is coordinating the federal response to situations involving hazardous materials in the region. The agency said people should stay away from any facilities that handle hazardous materials, including waste like propane, chemicals and oil. Instead, they should call the EPA's Midwestern regional office in Kansas City, Kan., to report potentially dangerous sites. That number is (913) 281-0991.

Mold: The hazard at home
The problems don't end, however, once you're back in your home, where mold can pose a significant danger.