Symptoms usually include watery diarrhea and stomach ache, but can also include nausea and vomiting, general ill feeling, and fever. Healthy people who contract cryptosporidiosis almost always get better without any specific treatment. Symptoms can come and go for up to 30 days, but usually subside in less. However, cryptosporidiosis can cause severe illness in persons with compromised immune systems, such as those with HIV infection or those taking drugs that suppress the immune system. Cryptosporidiosis is spread through fecal-oral transmission by feces of an infected person or an object that has been contaminated with the infected person's feces.
Infection can also occur if someone ingests food or water contaminated with the parasite.
The spread of cryptosporidiosis is highest among children who are not toilet-trained, and higher among toddlers than infants, probably due to the toddlers' increased movement and interaction among other children. For child care providers, the risk is greatest for those who change diapers. Cryptosporidium is tougher to kill than most disease-causing organisms. The usual disinfectants, including most commonly used bleach solutions, have little effect on the Cryptosporidium parasite. However, because ammonia has a strong odor and produces hazardous gas when mixed with bleach or other chlorinated solutions, hydrogen peroxide is probably the best choice in the child care setting.