From Slate: Chlorine isn't the answer for everything in public pools

This is a cautionary article about a nasty little thing called Cryptosporidium. It's something all pool operators need to consider and prepare for. Megan Cartwright has this article that appeared in Slate. Here is an excerpt:

     Unlike bacteria such as E. coli or parasites such as Giardia, Crypto can live for days in chlorinated water. It lurks in a protected form called an oocyst. When a swimmer swallows the oocyst, the parasite pops out and squirms into the cells lining his or her gut, where it multiplies. These new parasites then ride out the swimmer’s other end, with up to 100 million oocysts coming out in every fecal release.
     In 1997, 73 people came down with diarrhea from Crypto after playing at a sprinkler fountain in Minnesota; two years later, 38 got sick from Crypto and another bacteria after visiting a badly maintained splash fountain in Florida. In 2000, more than 200 swimmers in Ohio and Nebraska got sick. In 2005, more than 1,700 were infected with Crypto after playing at a New York spray park—a massive outbreak that led to a class-action lawsuit. Then in 2007, Utah suffered an outbreak of at least 1,900 cases, prompting officials to ban kids younger than 5 from public pools.
     So what’s behind the increase in outbreaks?
     For one thing, pool operators don’t often have the tools they need. Pools rely on chlorine to kill most germs, and it’s expensive and difficult to retrofit pools so their systems irradiate or add ozone to the water—methods that actually kill Crypto and are used nowadays by drinking water treatment plants.