Cryptosporidiosis, called "crypto" for short, is a waterborne illness caused by single-celled coccidian parasites called Cryptosporidium, and it's responsible for as many as 7.3 percent of all the diarrheal illnesses reported in developed countries. Prevalence of cryptosporidiosis is greater in developing regions that may not have reliable access to clean water sources and sanitation [source: Pearson]. There are more than 26 known Cryptosporidium species; among them, Cryptosporidium parvum and Cryptosporidium hominis, which are responsible for most human cases of the infection.
It takes as few as two to 10 cryptosporidia to cause cryptosporidiosis, an infection in the small intestine. Symptoms usually appear an average of seven days after becoming infected. Watery diarrhea is the most common symptom of a crypto infection. Other symptoms of infection include abdominal cramping, dehydration, fever, nausea, vomiting and weight loss.
Some cryptosporidia are resistant to the chlorine used to eradicate bacteria, parasites, viruses and fungi in all types of water sources, from swimming pools to public water systems, but infections are treatable. Patients are usually prescribed antiprotozoal medication, such as nitazoxanide, as well as fluid replacement. People with healthy immune systems typically get better within two weeks. Those with compromised immune systems are at the most risk of infection and complications.