About 50 cases were reported in August, more than four times the usual number said officials at the Colorado Department of Public Health and Environment.

The cryptosporidium parasite moves through human and animal feces, often in swimming pools, water parks, lakes and streams and, less frequently, in drinking water, The Denver Post reported Tuesday. Symptoms include watery diarrhea, stomach cramps and nausea, which usually pass in a few days.

The reported Colorado cases are spread along the Front Range and Western Slope and don’t appear to have one common source, health officials told the Post.