NEW YORK — Health officials say hotel pools and hot tubs are a major source of the stomach bugs people get from swimming. And they’re reminding people with diarrhea to stay out of pools, hot tubs and water playgrounds.

U.S. public health officials report on safe swimming every year. Thursday’s version from the Centers for Disease Control and Prevention focused on outbreaks in 2000 through 2014 that were tied to swimming or bathing in treated recreational water spots.

In an average year, there were 15 such outbreaks and about 1,800 related illnesses. Overall, a third were tied to hotels.

A parasite called cryptosporidium (kript-toe-spor-ID’-ee-um) caused most of the outbreaks. It can survive normal chlorine levels, which is why people with such illnesses are urged to refrain from swimming.