#This article has been kindly provided by Health Leader

Summer. Translated into the language of liquid fun, it means water parks, river rafting, neighborhood pools and beaches. It also means uninvited guests that are doing the backstroke with you, like bugs.
And not the winged variety flitting around the surface. Think parasites with hard bodies resistant to chlorine that people don't even know they are harboring or spreading.
The result is a poolside view from the restroom.

What Lurks Beneath

In contaminated water, not only might you find E. coli, and other moderately scary viruses and bacteria that will literally make your skin crawl, but also a parasite, Cryptosporidium, nicknamed, crypto. "It's very small about the size of a red blood cell, and very difficult to filter out of the water," says Cynthia L. Chappell, Ph.D. and professor in the Division of Environmental and Occupational Health at The University of Texas School of Public Health at Houston.

Cryptosporidium infects many animal species, including cows and horses, that then spread it to humans, says infectious disease specialist Pablo C. Okhuysen, M.D., professor in internal medicine at The UT Medical School. He points out that, "It takes only a few parasites to infect someone, but an infected animal can pass several million a day."

Hard to Crack

Another feature of Cryptosporidium is that it exists in water as an oocyst form: in other words, one really hard-shelled yoke. It has a Teflon-tough outer covering that protects it in an adverse environment-so well that adding chlorine to the water isn't very effective. "Chlorine will only kill a portion of the parasites, and only if they are in contact over a long period of time," Chappell says.

Cryptosporidium can live in fresh water for months. Chappell says that in pools and water parks, even a "shock" procedure (chlorine raised to extreme levels that would kill most bacteria and viruses) still might not penetrate this parasite's shell.

In a healthy person, the diarrhea caused by crypto may last only a few days. Danger of dehydration is the biggest problem people might have.

Specific populations are at risk for complications-the very young and old, those with compromised immune systems from illness or certain medications, or dialysis patients. "Most people resolve it on their own," Okhuysen says, but adds, "If you have prolonged diarrhea, Cryptosporidium might be one of things that could be causing it."

Water Park Blues

Chappell says that public recreational facilities boost the number of outbreaks. "If you look at the reported cryptosporidiosis cases in any one year, and we repeat this year after year, you'll see a big spike in the summer.