Thu Jul 1, 3:06 PM ET Add Health - Reuters to My Yahoo!

By Paul Simao

ATLANTA (Reuters) - Americans dipping into the warm bubbles of a hot tub may be getting a lot more than heat.

More than half the hot tubs and spas in U.S. hotels, campgrounds, gyms and other areas open to inspection violate local or state health regulations, the Centers for Disease Control and Prevention said on Thursday.

Inspectors found at least one problem with water chemistry, filtration and circulation or basic spa management on 56.8 percent of their 5,209 visits to sites in Florida and four other states in the summer of 2002.

Eleven percent of inspections resulted in the immediate closure of spas, according to the study, the first time the CDC has examined data from public spa inspections. The agency based its findings on data from state and local officials.

Poor hot tub maintenance can create a perfect environment for the spread of the bacteria that cause skin rashes and respiratory infections. There were 13 reported outbreaks linked to hot tubs between 1999 and 2000, affecting 183 people.

U.S. health officials, however, estimate the real figure for such skin and respiratory illnesses is much higher.

"We suspect this is only the tip of the iceberg," said Mike Beach, a CDC epidemiologist and one of the researchers of the study. "A lot of these outbreaks occur and just never get reported."

Beach noted that much of the risk of getting sick in a hot tub, whirlpool or spa could be eliminated if owners ensured that they and their staff were properly trained in the use of disinfectant and other basic maintenance.

There are an estimated 5 million hot tubs, whirlpools and spas in public and private use in the nation.