But they'll be back at pools this summer. Talcott is teaching Hayden to keep water out of his mouth and they "hope to goodness we don't get it again."

Health officials are relying on more than hope to prevent another outbreak this swim season.

Slow to recognize last year's outbreak - which gave hundreds of Utahns violent diarrhea and stomach cramps so severe they resembled appendicitis - they are working to shave detection time.

Pool operators, some of whom fueled the epidemic by letting employees swim sick, are trying to restore confidence by making investments large and small, from adding expensive water treatment systems to buying soap dispensers.

But changes will mainly focus on who health officials say was the biggest culprit: Swimmers, diapered and adult alike, who dove into pools knowing they were sick.

Signs will ask you to leave if you've had diarrhea within the last two weeks. Lifeguards will blow the whistle if you're spitting water, since crypto is spread through fecal-oral contact. And posters will offer this reality check: Pool water isn't sterile. It's like taking a bath with strangers.

"You might as well be naked," said Ron Tobler, program manager over environmental health for the Utah County Health Department. "Our burden before entering the next swim season is truly educating our citizens . . . you are that exposed."

Starting small. Health officials think Utah's "case zero" - believed to be two children who got crypto and started its spread - picked up the parasite from a dog, cow or lake in Utah County.

They repeatedly swam while sick, Tobler said. And the disease is unfortunately easy to spread. A single bowel movement can release 1 billion crypto organisms but it only takes ingesting 10 to 30 of them to get sick. Humans excrete them for up to 50 days, even when they don't have diarrhea. The parasite is resistant to chlorine.

"It's designed for swimming pool transmission, in a way," says Robert Rolfs, state epidemiologist.

But epidemiologists are still at a loss to explain what changed last year, to cause a jump from the normal 15 reported cases a year to 1,900.

Hypotheses include the hot weather that led more people to the pools, a stronger parasite, or new pool filters that may not work as well as older systems. There may have been more reporting, because more people saw doctors - due to publicity and because a drug treatment has recently become available.

Plus, people who swim like variety. Two sick people in Salt Lake County swam in more than 18 places.

"Maybe it was just bad luck," Rolfs says.

Catching on. Looking back, Rolfs is disappointed in health officials' response times. "We have to figure out a way to detect it sooner," he said, pointing to one telling statistic: 50 people got the parasite during the week of July 22, but only 5 cases were immediately reported.

The problem: people with diarrhea didn't go to a doctor early on, doctors didn't automatically test for crypto, and labs took days to report when the parasite was found. In late May, when the cases first started, it took 90 days from when someone became sick to when the state was notified. On average, the lag time in Salt Lake County was up to three weeks.

"By the time we recognized it and were able to react . . . the number of people who can give it to other people was pretty big," Rolfs said.

Health officials told pools to hyperchlorinate - which led to chemical burns, hair loss and skin irritation at some pools. Later, on advice from the Centers for Disease Control and Prevention, Utah became the first state to turn away children, at first excluding those in diapers and then all kids under 5.

Crypto cases dropped, but that could be due to school starting and families abandoning the pools.

Utah County's Tobler believes pools should have been closed. Technology and chemistry "can't stop it if people keep coming to the pool sick," he said.

For this summer, Rolfs is exploring why a tracking system for emergency room visits - set up during the Olympics to detect bioterrorism - didn't detect crypto. A system that monitors sales of anti-diarrheal medicines also didn't catch the outbreak and may need tweaking, he added.

Pools at fault? The sick who were interviewed named over 400 public and private pools where they swam statewide, though epidemiologists can't say if all of those pools were infected. And investigators couldn't pinpoint any particular pools as the cause.

Utah County officials discovered many municipal and commercial pools had allowed sick lifeguards to swim, mistakenly believing they had the flu or heat stroke. That error "helped fuel the epidemic," a county report said.

But generally, state and local officials in charge of pool quality complimented pool operators' cooperation.

Garth Miner, an environmental scientist with the Utah Department of Health, expected to find pools with low levels of chlorine or high levels of cyanuric acid, which slow chlorine's ability to kill microorganisms. He didn't.

The state is nevertheless weighing changes for pools, including mandated recording of fecal accidents. If they find diarrhea, some pools would have to shut down for 24 hours to decontaminate. The state may eventually require new treatment systems, like ultraviolet technology, which is better than chlorine at killing crypto, but isn't foolproof.

Salt Lake County is voluntarily spending $1 million to add the system to its 18 public pools this season.

Babies unfairly blamed: Children suffered the most from the outbreak, and they've taken most of the blame, perhaps unfairly.

Those ages 0 to 9 make up 18 percent of the population but comprised a whopping 52 percent of the sick.

But data shows the potty-trained may share the blame: Of 563 sick people surveyed, 28 percent admitted to swimming while sick; 87 percent of those were 5 and older.

"Some said if they stopped swimming they'd get fat," says Teresa Gray, in charge of water quality and hazardous waste for Salt Lake Valley Health Department. "This was their routine."

Still, many adult swimmers want the babies out. Others, like Alan Sparrow, want separate pools. The 57-year-old Salt Lake City resident has skipped his usual swim since diapered children were allowed back in.

"This isn't about being supportive of families with children or not, it is about keeping everyone - children and adults - healthy," he wrote in an e-mail.

For now, lifeguards and instructors plan to emphasize new habits this swim season, which starts Memorial Day weekend.

A proposed rule calls for continuing to welcome babies, while requiring children under 3 to wear tight-fitting diapers. Martin Jensen, spokesman for Salt Lake County's public pools, says instructors will warn children not to get water in their mouths.

Lifeguards will be watching to ensure swimmers have showered - another proposed rule specifies a "cleansing shower" with warm water and soap to remove fecal matter.

"This contamination is from people continuing to swim when ill with diarrhea and parents who are not saying no to young children who have diarrhea," says Michael Beach, the CDC's acting associate director for healthy water. "This will never be fixed without the public cooperating."

hmay@sltrib.com