There are blatant errors in the article.
Cryptosporidium is correctly referred to as a parasite since it is more specifically a protozoan oocyst when in water, but it is also incorrectly stated as a bacteria which it clearly is not. The article says that it is common, but it is not like fecal bacteria (e.g.
E. coli) we all have nor is it like soil or skin bacteria (e.g.
Pseudomonas) or even viruses or blown-in algae spores.
As noted in the
Cryptosporidiosis Surveillance — United States, 2011–2012 report, there are estimated to be around 750,000 cases of cryptosporidiosis annually in the U.S. (though only around 2% are reported) so that's around 0.2% of the U.S. population (1 in 500). The highest incidence rate is with children aged 1-4 at 6.6 per 100,000 population. Since only around 6% of cases are associated with outbreaks with treated recreational water (e.g. swimming pools), most cases with children are likely to be direct fecal-to-oral child-to-child contact in day care centers or other places where small children are in close contact.
The main problem with this disease regarding swimming pools is that it only takes one infected person with diarrhea to go to a commercial/public swimming pool and infect dozens to hundreds of others where such infection continues for many days or even weeks before an outbreak is detected, traced, and the pool shut down and treated. On the other hand, it's far less likely for this disease to be spread in residential swimming pools, if for no other reason people taking more care to not have people with diarrhea using their pool.
There are basically three ways that a pool can be cleared of Crypto: 1) use of a supplemental disinfection system such as UV or ozone, 2) use of a powerful coagulant such as
HaloSource SeaKlear PRS Stage 1 and 2, or 3) overnight use of chlorine dioxide generated by adding sodium chlorite to water with chlorine and CYA. A fourth method of superchlorination to 10 or 20 ppm FC only works if one has no CYA in the water. With CYA, one would have to have the FC by 10 or 20 ppm higher than the CYA level which generally makes this impractical unless the CYA level is low.
