Contact must then be transferred to the mouth and swallowed. It is especially prevalent amongst those in regular contact with bodies of fresh water including recreational water such as swimming pools. Other potential sources include insufficiently treated water supplies, contaminated food, or exposure to feces. The high resistance of Cryptosporidium oocysts to disinfectants such as chlorine bleach enables them to survive for long periods and still remain infective. Some outbreaks have happened in day care related to diaper changes.The following groups have an elevated risk of being exposed to Cryptosporidium:
Child care workers
Parents of infected children
People who take care of other people with cryptosporidiosis
International travelers
Backpackers, hikers, and campers who drink unfiltered, untreated water
People, including swimmers, who swallow water from contaminated sources
People who handle infected cattle
People exposed to human feces through sexual contactCases of cryptosporidiosis can occur even in cities that have a properly de-contaminated water supply. In a city with clean water, it may be that cases of cryptosporidiosis have other origins. Testing of water, as well as epidemiological study, are necessary to determine the sources of specific infections. Cryptosporidium is causing serious illness  more frequently in immunocompromised than in apparently healthy individuals. It may chronically sicken some children, as well as adults who are exposed and immunocompromised. A subset of the immunocompromised population is people with AIDS. Some sexual behaviors can transmit the parasite directly. Life cycle
Cryptosporidium spp. exist as multiple cell types which correspond to different stages in an infection (e.g., a sexual and asexual stage).
Ten percent of the population in developing countries excretes oocysts. In developed countries, the number is lower at 1–3%. The age group most affected are children from 1 to 9 years old.In Eastern Europe cryptosporidiosis in humans and animals is common, but there are considerable gaps in surveillance and a lack of comparable methods which is limit the understanding of the disease and detection of outbreaks. Research show a rich diversity of zoonotic subtypes of the parasite in animals indicating a rich potential of animal to human transmission. Roughly 30% of adults in the United States are seropositive for cryptosporidiosis, meaning that they contracted the infection at some point in their lives. History
The organism was first described in 1907 by Tyzzer, who recognised it was a coccidian. Research
A recombinant Cryptosporidium parvum oocyst surface protein (rCP15/60) vaccine has produced an antibody response in a large group of cows and also antibody response in calves fed rCP15/60-immune colostrum produced by these vaccinated cows. This is very promising. Human Cryptosporidium parvum infections are particularly prevalent and often fatal in neonates in developing countries and to immunocompromised people, such as AIDS patients. There is no commercially available effective vaccine against Cryptosporidium parvum, although passive immunization utilizing different zoite surface (glyco)proteins has shown promise. Developmental stages of the life cycle of the parasite might act as possible targets for vaccine development. The organism is detected in 65–97% of the surface-water supply in the United States and is resistant to most disinfectants used for the treatment of drinking water.