Cryptosporidium:

Cryptosporidum is a pathogenic, single-celled organism that lives in animals and may contaimnate water sources if infected animals live near them. When a human drinks this water, sporozites from the protozoa are relased into the body and may invade the inner lining of the gastrointestinal tract. This may cause the illness cryptosporidiosis. This illness is very uncommon in healthy people; if may harm infants, the eldery, and people with depressed immune systems, which include people with HIV and cancer. If the bottled water source is underground, it is difficult for cryptosporidium to infect it. If the water is from a municipal source, it has been treated for this organism. A problem with cryptosporidium, however, is that chlorine and other chemicals have difficulty killing it. Therefore, non-chemical techniques are required to take care of it.

In many of the debates over bottled water safety, this organism is a major player.

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