Just when you thought it was safe to go back into the water, the CDC issued a new report that may give you pause. A parasite that causes diarrhea and is often spread through water is causing an escalating number of outbreaks in the United States, and disinfecting pools and hot tubs doesn't stop it.

The parasite, called Cryptosporidium, also known as Crypto, is protected by an outer shell that allows it to survive outside the body for long periods of time and makes it resistant to chlorine disinfection.

In fact, most of the outbreaks of disease-causing organisms — 77 percent — are linked to water treated with chlorine or bromine, such as swimming pools, hot tubs, and spas. The remaining 23 percent of outbreaks, according to the CDC were tied to untreated water such as lakes and oceans.

Although other water-borne organisms can cause illness, Crypto is responsible for about 50 percent of those caused by treated water.

The number of outbreaks continues to rise, but scientists are unsure why. "When people get sick with diarrhea, they often think that something they ate caused the symptoms," said Michele Hlavsa, an epidemiologist with the CDC. That may be changing, and now "people are realizing it's not necessarily only about where they ate or what they ate. It could be about where they went swimming," she told Live Science.

But the CDC doesn't recommend people avoid the water. "Swimming is an excellent way to get the physical activity needed to stay healthy," Hlavsa told CBS. "However, pool users should be aware of how to prevent infections while swimming. Remember, chlorine and other disinfectants don't kill germs instantly."

To stay healthy and to also avoid spreading pathogens, the CDC offers the following tips:

● Don't go into the water if you have diarrhea.
● Shower before getting into the water.
● Don't urinate or defecate in the water.
● Avoid swallowing the water.

The report is published in the CDC journal Morbidity and Mortality Weekly Report.