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Cryptosporidium parvum causes cryptosporidiosis, a parasitic infection. The symptoms of cryptosporidiosis are: watery diarrhea, stomach cramps, dehydration, nausea, vomiting, fever, and weight loss. In healthy people, the disease created by the parasite is self-limiting, but in immunosuppressed individuals, the disease may be chronic and severe.


The parasite can infect many species, such as, humans and many types of animals.

Transmission / Exposure Route

The fecal-oral route is how cryptosporidium parvum transmits the parasite. It mostly occurs through person to person contact. It can also be transmitted through animal contact, ingestion of water, or through food. Ingestion of water, especially swimming water, has been creating a major waterborne outbreak. The sporulated oocysts have been found in feces throughout the infection. Children and caregivers helping the ill are at an increased risk of infection.

Case Fatality Ratio

Mortality is generally low in immunocompetent patients. In immunodeficient patients, the infection can be persistent and severe. The mortality rate for children less than five years of age was 2.6/10,000/day during the outbreak. 73% of AIDS patients with an extremely low CD4 count died within the first year of contracting an infection. 

Incubation Period

Approximately 1 to 12 days.

Burden of Disease

In the United States, an estimated 748,000 cases of cryptosporidiosis occur each year[1] An estimated 30% of the adult population of the United States is seropositive for cryptosporidium[6] During 2006 - 2008, the number of reported cases of cryptosporidiosis increased from 6,479 in 2006 to 11,657 in 2007, and then decreased to 10,500 in 2008. A greater number of case reports were received for children aged 1--9 years and for adults aged 25--39 years than were received for persons in other age groups. Peak onset of illness occurred annually during early summer through early fall[7] 

In 1993 an estimated 403,000 of the greater Milwaukee, Wisconsin area became ill with cryptosporidiosis among 880,000 possible exposures (An attack rate of about 45.8%)[8]

Internationally (including Latin America, Africa, the Middle East, and South Asia), about 13% of stool samples analyzed for parasites in developing countries reveal Cryptosporidium oocysts (Cabada, M, et al. 2011). 

Duration of Infectiousness and disease


Excretion Rates (see Exposure)



C. parvum is a coccidian parasite. It is classified as a Sporozoa, since it releases sporulated oocyts, which are infectious and about 5 microns in size. 

Enviromental Survival

They are highly resistant to chlorine and can survive for 2 to 6 months in a moist environment. 

Dose Response Model

Route: oral, Response: infection


\[P(response)=1-exp(-k\times dose)\]

Optimized parameters:
k = 5.72E-02
ID50 = 1.21E+01

Data from Other Sources


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Other names:

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NCBI Publications on Risk Assesment:

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