CDC Sees Increase of Pool-Borne Illness

May 25, 2001 — -- Be careful how you swim. You could catch something.

Federal health officials are launching a campaign to promote healthy swimming, as pool-borne illnesses have more and more people coming down with diarrhea, stomach aches and other maladies.

"In the past 10 years, those [reported pool] outbreaks have involved over 10,000 people," says Dr. Michael Beach, an epidemiologist for the federal Centers for Disease Control, which is running the public awareness campaign. "The public generally isn't aware that pools can transmit illness."

Health officials are particularly worried by a rise in cryptosporidium, a type of bacteria that can survive for days in chlorinated water before it's killed. It now accounts for 80 percent of pool-borne diarrheal illness, Beach says.

The recent surge in cases has federal health officials warning the public to take precautions when splashing around — including not swimming when ill with diarrhea and not swallowing pool water.

By far the greatest number of outbreaks occurred in the CDC's most recent two-year period of analysis, 1997-98, when there were 10 reported diarrheal illness outbreaks in pools. Until 1993-94, there had typically been just two or three reported outbreaks every two years.

Ten outbreaks may not seem like a lot at first glance, say officials, but each outbreak typically affects hundreds of people. And the reported cases are believed to be merely "the tip of the iceberg," Beach says, because few people report severe cases of diarrhea to local health officials, who would then report through a chain of agencies to CDC.

Cryptosporidiosis is marked by long-term diarrhea, cramps and vomiting. Patients with the bacterial disease generally must recover on their own, as there is no effective treatment, Beach says. Normally, they do recover, although the cryptosporidium bacteria can be life-threatening to people with lowered immune systems.

Cryptosporidium is tough to find and eradicate before people get sick, Beach says, because it is resistant to chlorine, it can exist in otherwise clean, well-maintained pools, and health officials can't detect it without "a very laborious test."

"By looking at a pool, it's an extremely difficult thing [to detect]," Beach says. "Even the best maintained pools can spread illness if they are contaminated."

All it takes is one person carrying the cryptosporidium bacteria to infect a pool, fountain or water slide, Beach says, making it important for people to take precautions.

"We're not trying to scare people off of swimming," Beach says. "We need them to start swimming responsibly.

"One of the key recommendations here is that we have to think that we don't swim if we're ill with diarrhea," he adds. "People need to think that they shouldn't be swallowing pool water. It's not drinking water."

In addition, people should not swim if they have had diarrhea within the past two weeks; diapers should not be changed near where they can contaminate a pool; good hygiene such as frequent hand-washing should be practiced; and children should be encouraged to take frequent bathroom breaks, officials say.

Beach adds that people should not go swimming at all during known outbreaks in their community, even if a pool believed to have spread disease has been closed. A case study just published by the CDC highlights the difficulty in controlling a cryptosporidium outbreak.

"Eighteen percent of the people in the Nebraska survey admitted that they continued to swim even though they were still ill," Beach says. "In some cases, the pools were closed, and the people began swimming at other local pools."