When caused by Crypto, the disease is called cryptosporidiosis. The incubation period for the disease is 4 to 14 days i.e. symptoms begin to show up as early as 4 days or as long as 14 days after exposure. This category of individuals includes cancer patients undergoing chemotherapy, organ transplants, AIDS patients, persons with viral illnesses such as chicken pox or measles, and malnourished children and the elderly. The symptoms in immuno-compromised patients mirror those in normal patients except they develop a more severe infection with diarrhea that may persist for months or years. There is no current effective drug therapy for cryptosporidiosis.
Treatment usually focuses on rest and control of dehydration.
As of November 1995 there were nine drugs for the treatment of cryptosporidiosis in some stage of the U.S. Food and Drug Administration approval process. Exposure routes include handling diapers from an infected child or caring for an infected patient, handling or coming into contact with infected pets or animals, or through contact with contaminated food or water. Exposure to waterborne Crypto in lakes, swimming and wading pools and public water supplies poses the greatest threat because of the potential to infect large numbers of people very quickly. Surface waters are the most common source where oocysts can be detected. Contamination depends on both the characteristics and degree of protection of the watershed.