Studies indicate that as few as 10, and perhaps as many as 500 Oocysts are required to initiate infections in mammals. The infectious dose for humans is thought to be fewer than ten. Cryptosporidiosis typically lasts 10 to 14 days. However, it may linger off and on for up to 30 days and infrequently can persist for extended periods. A rapid cure for Cryptosporidiosis has not been found.
Recovery depends on the patient's overall health and immune system.
The disease can be fatal for those who are already in a fragile state such as someone with AIDS or any other weakness to their immune system. The thick walls of the Oocysts make it difficult, almost impractical, to kill with the UV systems in most domestic water treatment systems. Also, the cyst is much more difficult to kill using chlorine than normal coliform bacteria found in water supplies. Cryptosporidium is a one-celled parasite that can cause a gastrointestinal illness called cryptosporidosis. Cryptosporidium occurs in the feces of infected animals or humans.