...Like Cryptosporidium.  It is the cause of an Alabama water pak being temporarilty closed until they "super chlorinate" the water, planning to be running in time for this weekend, August 20 and 21.

The Spring Valley Beach Water Park in Blountsville, Alabama, was closed this weekend after health officials traced a parasite called cryptosporidium to the park. The microscopic parasite can survive in properly chlorinated water for days and can cause nausea, diarrhea and stomach cramps, according to the U.S. Centers for Disease Control and Prevention.

Symptoms of cryptosporidium usually last about a week.

"It is introduced to the water from an outside source and is most commonly transferred in recreational water," park officials said on Saturday. "Though we test our water every two hours throughout the day, there is no simple test for this particular parasite."

(via "Alabama Water Park Temporarily Closed After Parasite Found")

The Cryptosporidium parasite was in the news last summer too:

Outbreaks related to pools, hot tubs and other recreational uses of water can be dangerous, and according to a new report released today, the U.S. Centers for Disease Control and Prevention found that 90 outbreaks between 2011 to 2012 resulted in 1,788 illnesses, 95 hospitalizations and one death.

A major cause of the outbreaks in treated water, including hot tubs and pools, is a hardy parasite called Cryptosporidium, which is encased in a tough shell and causes acute gastrointestinal issues such as diarrhea.

Michele Hlavsa, chief of the CDC's Healthy Swimming Program, said the parasite is particularity troubling due to how long it can live in treated water.

"It can survive for 10 days," Hlavasa told ABC News, noting that other bacteria including E. coli are killed in minutes to hours in a treated pool.

"With these outbreaks, we see they disproportionately affect young children," Hlavasa said. "They’re the ones who can go to a pool and young children tend to carry lots of germs."

The parasite can be cleared from the body in about two to three weeks, Hlavasa said, but in a person with a weakened immune system the condition may become chronic or even fatal.

Because of gastrointestinal issues such as diarrhea, "you’re losing so much and your body isn’t able to absorb nutrients," Hlavasa said.

(via "CDC Warns of Pool Parasite This Summer")