Bob Hancock, director of the UBC Centre for Microbial Diseases and Immunity Research, says swimming carries lesser risks compared to other summer hazards, like improperly grilling a burger. However, he cautioned that although the danger of infections isn’t that high, it always pays to be careful.

For example, Hancock said that swimming with too many people in the shallow waters of a beach boosts the chance of getting ill from E. coli. These bacteria are found in the digestive tracts of warm-blooded animals.

The UBC professor also said disease-causing bacteria like Shigella and Salmonella are likewise found near beaches. These come from the feces of animals and can cause stomach problems in humans.

People who want to cool off by dipping into small ponds of inland fresh water or rivers should be aware of two types of microscopic parasites: Giardia and Cryptosporidium.

Hancock explained that these come from either dead animals or fecal matter. Giardia and Cryptosporidium are known to cause gastrointestinal disorders. He added that these parasites are not common in big bodies of water like lakes.

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