What is the prevalence of cryptosporidiosis in the US?

Updated: Nov 11, 2019
  • Author: Melinda B Tanabe, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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Answer

The frequency of cryptosporidiosis has not been well-defined in the United States. Many laboratories do not routinely test for Cryptosporidium. Laboratories that test for Cryptosporidium often use insensitive tests. [1, 2] The number of reported cases has increased with increased awareness and improved diagnostic testing. From 2006-2010, the rate was between 2.3 and 3.9 cases per 100,000 population, with 13,453 cases reported in 2016. [20, 21] However, estimates suggest that the frequency of infection is likely to be 100-fold higher than the number of reported cases. [22]

Studies in the United States have documented cryptosporidiosis in about 4% of stools sent for parasitologic examination. Seroprevalence studies suggest that 25%-35% of the population in industrialized countries (including the United States) have had cryptosporidiosis at some time in their life. Cryptosporidium species also cause waterborne outbreaks of diarrhea. In 1993, more than 400,000 cases of diarrheal illness due to Cryptosporidium infection were reported in Milwaukee, Wisconsin. [23] Waterborne outbreaks continue to be common worldwide. [9, 10, 24]

Cryptosporidium parasites are ubiquitous, except in Antarctica, and infection is more common in warm, moist months. [1, 20] In the United States, the incidence peaks from July through September. In England, there are separate peaks, in the spring (associated with C parvum and farm animals) and the fall (associated with C hominis and recreational water). [10, 11] Outbreaks in daycare centers with incidence rates of 30%-60% have been reported. [25]

Prior to the availability of combination antiretroviral therapy, approximately 10%-15% of patients with AIDS developed cryptosporidiosis over their lifetime. As with other opportunistic infections, the prevalence of cryptosporidiosis in patients with AIDS has dropped dramatically. [26]


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