Parasites found in Alamosa, Colorado water

After three weeks of a boil-water advisory, the 8,500 residents were hoping for the all-clear today, so they could have a shower, brush their teeth, and maybe even a glass of water without hauling 5-gallon carboys of water around the house.

Oh-oh.

The U.S. Centers for Disease Control and Prevention, called in to help with the outbreak of Salmonellas that has so far sickened 389, found two different parasites — giardia and cryptosporidium — present in the water system before it was flushed with high doses of chlorine last week.

The city remains on a "boil order" requiring residents to boil water before drinking it or using it for cooking.

A thorough investigation into the intricacies of a municipal water supply becoming contaminated can be found in the Walkerton Commission of Inquiry, held after E. coli O157:H7 got into the water supply of Walkerton, Ontario in 2000, sickening half the town of 5,000 and killing seven.