Here Are Eight Ways You Can Stave Off Phoenix's Chlorine-Resistant Pool Parasite (Gross-Out Warning!)

Health officials have issued their second alert of the summer about a microscopic parasite that is spread in feces, can survive in chlorinated pools, and induces a nasty case of infectious diarrhea.

The 100 victims officials know about are just the tip of the iceberg, warns Dr. Rebecca Sunenshine, medical director for the Maricopa County Department of Public Health. Cryptosporidium, a one-celled protozoan microbe, has likely sickened hundreds of people in metro Phoenix in what has shaped up to be the one of the worst outbreaks in years.

"Any public recreational water facility, community pools, pools for working out, water parks, splash pads," Sunenshine says, ticking off a list of potentially infected sites. "We believe many, many pools have been affected."

Besides being one of the world's leading causes of diarrhea, the parasite is a fascinating creature in its own right. It lives in the human small intestine, and causes infection while simultaneously causing the body to release a protein that helps prevent it from killing its host. Once buried in the intestinal lining and breeding, the microbe begins producing armored shells — called oocysts — that house more microbes and are resistant to chlorine and to alcohol-based hand sanitizers. Swallowing a few of those oocysts mixed in with pool water can be all it takes to come down with a case of vomiting and watery diarrhea that can last for up to three weeks. Most victims recover on their own without treatment, but people with compromised immune systems are at greater risk.

With that in mind, here are eight tips from Dr. Sunenshine and the Centers for Disease Control and Prevention on how best to slow the outbreak and help you and your family maintain a solid stool:

8. If you or someone you know has diarrhea, don't get back in the pool for at least two weeks after it stops.

7. When you're swimming, especially in a public pool, try not to swallow the water. It's how the bugs get in.

6. If you have a private pool and never use public facilities, your pool is unlikely to have been infected. If you want to keep it that way, uninvite the typical crowd of pool bums and their poo-butt kids.

5. Don't rely on tests. Sunenshine says tests for cryptosporidium aren't reliable, showing plenty of false negatives and positives alike.

4. Treat diarrhea in the pool like the emergency it is. "Formed" fecal material is much less likely to release cryptosporidium. Get everyone out of the pool, make sure the filter's working properly, and hyper-chlorinate the water for 8 to 28 hours.

3. Consider using a condom if there's fecal-contact potential with a sexual partner who might be infected.

2. Don't expect your own impeccable bathroom hygiene to protect everyone else in the pool. If you have diarrhea, the microbe might still be present even after a stellar clean-up job. "They're microscopic, and they can live in the area right around where you do your business," Sunenshine says. "Just a few organisms can contaminate the entire pool."

1. Practice good hygiene, especially if you're around an avid swimmer or user of public water facilities. Cryptosporidium is very contagious. An infected person can easily infect others by touching something (such as food) with a contaminated hand. 

Good luck! Go forth and swim. And remember to drink plenty of liquids if the parasite finds you — it's not the diarrhea that kills you; it's the dehydration. Dr. Sunenshine says officials expect the problem to linger for months.
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Ray Stern has worked as a newspaper reporter in Arizona for more than two decades. He's won numerous awards for his reporting, including the Arizona Press Club's Don Bolles Award for Investigative Journalism.