The Colony Aquatic Park in Denton County followed all the rules. Shower before you swim. No spouting or spitting water. Enforced bathroom breaks. Even a high-tech water filter.
But the pool shut down briefly last week because of a chlorine-resistant parasite that's sweeping across North Texas. Since then, the pool's attendance has been so low that there's not enough money to cover the lifeguards' salaries.
"It's probably going to be that way for the rest of the summer," aquatics manager Elise Knox said. "People at this point are afraid to swim anywhere."
Across the country, growing numbers of people have reported infections with Cryptosporidium, a diarrhea-causing parasite passed on through the feces of animals and humans that's often contracted when someone swallows even a small amount of contaminated water.
And at the moment, North Texas is at the epicenter.
Dallas, Tarrant and Collin counties have confirmed more than 400 cases of cryptosporidiosis this year - mostly from the past few weeks. Last year, there were 62.
"I've been doing this close to 12 years, and I've never seen these numbers," said Zach Thompson, director of the Dallas County Department of Health and Human Services.
One possible explanation for the increase is that high gas prices prompted more people to stay closer to home during summer break this year. And when summer temperatures soared, many of them took to the water, Mr. Thompson said.
But overall, public health officials remain puzzled about exactly why the numbers are skyrocketing.
Their best guess? It could be as simple as increased awareness and reporting.
A well-publicized outbreak at Burger's Lake in Tarrant County last month, where a confirmed 88 people were infected, brought a once-under-the-radar parasite to the forefront of locals' minds, said Anita Kurian, the Tarrant County chief epidemiologist.
The Dallas County medical examiner's office is also investigating whether the death of a 6-year-old Richardson girl in late July was related to the parasite.
As news of crypto spread, people who developed diarrhea, abdominal cramping or vomiting started worrying about that instead of blaming a taco or greasy hamburger from the night before.
"Now they're thinking, 'Where was I swimming?' " said Michele Hlavsa, an epidemiologist who specializes in recreational water illnesses at the Centers for Disease Control and Prevention.
The national rise in reported crypto incidents also coincides with the release of a crypto drug treatment for people 12 and older about three years ago. A treatment for children 1 to 11 years of age became available a few years earlier.
Before then, many doctors didn't bother testing for cryptosporidiosis, Ms. Hlavsa said, and therefore didn't report it.
Even with growing awareness, people continue to unknowingly spread the parasite, which can be contagious for up to two weeks after symptoms subside.
About a third of those with confirmed infections in Dallas County said they went swimming while they were showing symptoms or during the two weeks afterward, according to Dallas County Health and Human Services. Within that period, they could still spread the parasite.
Testing the waters
People can be exposed to Cryptosporidium in a variety of ways. State and federal health officials say that contact with fecal matter in day care centers can lead to infections. It sometimes finds its way into drinking water or food. Most Texas cases have been tracked back to swimming pools, recreational lakes, and pool and spray grounds.
Communities typically take steps to ensure the safety of all pools used by the public. In Dallas, inspectors conduct several water quality tests, including chlorination and pH levels. In more than half of the 184 inspections reviewed by The Dallas Morning News last week, the pools failed water quality tests. But whether the pools passed inspection or not, Cryptosporidium could be present.
"If you have an E. coli outbreak, it's probably because the pool is not well-maintained," Ms. Hlavsa said. "But with crypto, that's not true."
Code enforcers typically don't test for the parasite, so a number of local public health departments are recommending that swimming facilities "hyperchlorinate" their water at least once a week to curb the parasite before it becomes a problem. To do that, pool operators have to close the pool, raise the chlorine level and then return the chlorine level to normal before it reopens. Ultraviolet filtering systems can also kill the parasite but can be expensive to install.
Individuals, however, can do a lot to reduce the risk through good hygiene.
All areas vulnerable
Texas has had more than its share of cryptosporidiosis cases this year, but other areas may be just as vulnerable.
"It can happen anywhere," said Emily Palmer, a spokeswoman for the Texas Department of State Health Services. "It's not something that's endemic to one part of the state or another."
In 1993, news accounts reported that crypto-contaminated drinking water infected more than 400,000 people and contributed to more than 100 deaths in Milwaukee.
Last year, more than 1,900 cases were confirmed in Utah after an outbreak in swimming areas. In response, state officials mandated weekly hyperchlorination and banned children 5 and younger from swimming in public pools.
"Swimming in diapers is not always the best thing to do," Ms. Palmer said.
Utah did see a dramatic drop before the end of 2007 in the number of crypto cases, but it was unclear whether that was because of the measures state officials took or the end of the swim season.
Since then, public health departments across Utah initiated a massive education campaign that involved meeting with everyone from inspectors to rotary clubs to lifeguards and airing informational TV commercials, said Teresa Gray, who manages water quality in Salt Lake County.
So far this year, Utah has seen only one confirmed crypto case. Texas public health departments will consider similar regulations if the problem worsens.
"We haven't reached that stage yet," said Dr. Kurian of Tarrant County. "But I can't say that we will never make that recommendation."
Local health departments are trying to reach out to as many people as possible.
"If there's not recognition, then the cycle is going to continue," said Wendy Chung, chief epidemiologist for Dallas County.
For The Colony Aquatic Park, this means hanging up posters with messages like "Got Diarrhea? Don't Swim" and "You wouldn't drink your bathwater, would you? Why would you drink your pool water?"
Though Ms. Knox is taking all the precautions to avoid another crypto incident, she hopes it won't disrupt people's routines.
"In flu season, are you staying home from church and the movies?" Ms. Knox said. "Or are you living life?"
Staff writer Ryan McNeill contributed to this report