Cysts are chlorine-resistant microorganisms. When ingested in drinking water, they most commonly cause gastrointestinal illness, accompanied by vomiting, diarrhea, and cramps.
Chlorine-resistant "capsules" such as cryptosporidium and giardia, which contain parasites. If ingested, cysts can cause disease with symptoms of severe abdominal cramping and diarrhea.
any of a group of microorganisms that include entamoeba, giardia and cryptosporidium; when ingested, cysts can cause gastrointestinal illness among others and often have more problematic effects on children, the elderly and people with immune deficiencies