New report finds between 2009 and 2010, there were 81 outbreaks and 1,326 cases of illness in the United States linked to recreational water exposure (in pools, lakes, hot tubs, etc.).
Eighteen of these outbreaks (22 percent) were linked with hot tubs or spas, and about 40 percent of the outbreaks occurred in February or March, according to the report from the Centers for Disease Control and Prevention. Many of the winter outbreaks occurred in hotels.
One of the most common illnesses linked with hot tub/spa outbreaks is infection with the bacterium Pseudomonas aeruginosa.
Healthy people can develop Pseudomonas aeruginosa infections, including ear infections or skin rashes, after exposure to hot tubs that have not been properly chlorinated, according to the CDC.
Called "hot-tub rash," the infection often appears in the shape of the bathing suit a person is wearing, because the suit holds the contaminated water, Michele Hlavsa, an epidemiologist at the CDC's Waterborne Disease Prevention Branch, said.
Because of the high temperature in hot tubs, it can be hard to keep the level of disinfectant as high as it needs to be, Hlavsa told Live Science.
The report is published in the CDC's Morbidity and Mortality Weekly Report.