Cryptosporidium is highly resistant to chlorine and other disinfectants, which are used to kill bacteria and viruses in drinking water. In addition, Cryptosporidium is so small that it is not easily removed from water by the type of filters used in conventional municipal water treatment. Over half of the tested public water supplies that use surface water have been found to have small amounts of Cryptosporidium in the water sent to homes and businesses. You cannot tell without expensive, special tests. These tests are not very good for home use, and are not always reliable.
Diarrhea can cause dehydration.
Persons with diarrhea should contact their health care provider who may recommend an oral rehydration therapy mix. It depends on your health and your drinking water. If you have AIDS, if you have cancer or if you have had an organ or bone marrow transplant or are taking drugs that weaken your immune system, or if you were born with a genetically weakened immune system, you may want to take extra measures. You should talk to your health care provider regarding the level of your risk and on how to reduce it. If you have a healthy immune system, you are at less risk for cryptosporidiosis, but you may want to consider the quality of your drinking water.