CEDAR RAPIDS &#8212 At least 17 cases of the waterborne disease cryptosporidiosis are being investigated in eastern Iowa, state health officials said.

All of the cases were reported in the same county, and most of the patients were under 18 years old, said Iowa Department of Public Health spokesman Kevin Teale. He would not say which county.

A parasite causes the disease, commonly known as “crypto.”

Symptoms include watery diarrhea, dehydration, cramps, fever and vomiting, and can last up to two weeks.

According to the U.S. Centers for Disease Control and Prevention, swimming pool-associated outbreaks of cryptosporidiosis, which is resistant to chlorine, point to the need for changes in the way recreational water facilities are built and disinfected.

Teale said the illness can be avoided by thorough hand washing, by not swallowing water while swimming and not drinking untreated water.

He said people with diarrhea, especially children in diapers, should avoid swimming.