Following an unprecedented outbreak of cryptosporidiumaround Salt Lake City, Utah health officials took the extraordinary measure of banning children under age 5 from public pools, including gyms and apartment buildings.

?[To my knowledge], this is the first time we?ve ever had this level of outbreak,? said Rob Tobler, program manager at the environmental health division of the Utah County Health Department. ?Everyone?s kind of hoping that we?ll put out the fire right here.?

As of press time, approximately 1,828 Utah swimmers reported being infected by cryptothis year, far above the average of 30 reports annually. Salt Lake County, which has 1,031 swimming pools and normally experiences approximately 10 cryptocases a year, has documented more than 490 cases in 2007 so far. Health officials said all but one of the 700 public-access pools in Utah County, south of Salt Lake City, have been exposed to the parasite. Because most people don?t visit the hospital after getting sick, state health officials speculate that the actual number of infected swimmers in Utah could be 10 times as high.

Cryptocan cause severe diarrhea and most often infects a pool through just a tiny amount of fecal matter. It also can live on flotation devices, chairs and wet towels.

?One bout of diarrhea in a pool can contaminate 100,000 gallons of water. It takes less than 10 parasite occysts to make somebody sick,? said Diane Raccasi, epidemiologist at the Utah Department of Health in Salt Lake City.

The state of Utah doesn?t have the authority to impose the toddler ban, but it can recommend the measure to each county issuing permits for public pools. And every county in northern Utah that has experienced the outbreak has complied.

The affected counties are requiring all public pool operators to hyperchlorinate their water at least once a week which is the recommendation of the Centers for Disease Control and Prevention, based in Atlanta.

This was a tough summer for crypto. Aquatic outbreaks were reported in several states, according to Michael Beach, epidemiologist and acting director for healthy water with the CDC. He also supports the ban, noting, ?It?s important that public health professionals get the message out that anyone suffering from diarrhea shouldn?t go in a pool.?

In Utah, the first cryptocases appeared in July, and numbers exploded in August. Health officials suspect that higher than normal temperatures and increasing bather loads in multiple bodies of water sparked the outbreak.

In addition to the ban on toddlers, the Utah health department also recommends that people with severely weakened immune systems not swim in the state?s public pools until the outbreak is over.