Although several "crypto" outbreaks have occurred in the U.S., the most severe problem is in Africa where both the sanitary conditions are poor and a significant portion of the population has HIV. It is especially dangerous for people with a compromised immune system because it can lead to severe diarrhea and lethal dehydration. the most notable being a cholera epidemic in London in 1854.
A study published in the February 2004 issue of Vadose Zone Journal, which was funded by the USDA-National Research Initiative program and performed at Cornell University Department of Biological and Environmental Engineering, examines how C. parvum oocysts may be transported via preferential flow to groundwater.
A simulation model was developed on the basis of an existing preferential flow model. Column experiments with sandy and undisturbed structured soils were performed. Calf manure with cryptosporidiosis was applied to the columns soil surface, followed by rain. Chloride was also added as a tracer.
"Traditionally, people assume that soils filter out pathogens. This is based upon the premise that water and pathogens move slowly through all of the soil. We found that for sandy soil, where water moved rapidly through, there was indeed very little filtering initially. Surprisingly, the undisturbed, structured columns with large macropores had only a very limited breakthrough," said Tammo Steenhuis, Cornell University, who was one of the researchers of the study.