Last summer, Curtis Suttle took a BBC crew out on a boat to English Bay. The team was doing a documentary about how dangerous viruses are, and the associate dean of the UBC faculty of science decided to demonstrate something.

Suttle, who teaches in the departments of microbiology and immunology, earth and ocean sciences, and botany, wanted to show that most microorganisms are harmless to humans. So what did he do? The UBC professor drank water straight out of the bay and proclaimed to the TV crew that he had just imbibed more viruses than there are people on Earth. He only has one complaint.

“It’s a little too salty,” a laughing Suttle told the Georgia Straight in a phone interview. “The thing that killed me was they kept having to shoot it over and over again.”

According to Suttle, there are millions of microbes in all natural waters. Swimmers can even swallow some. “They don’t make us sick at all unless you should happen to get one which is a human pathogen, and that invariably would come as a result of contamination from sewage,” Suttle said.

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.

“It’s present in every single person,” Hancock noted in a phone interview with the Straight. He added that some strains can cause a range of infections, with diarrhea the most common.

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.

So is it a lot safer to stick with swimming pools? Not so much, really, according to Hancock.

Although pools are treated with chlorine and are reasonably safe, Hancock pointed out that bathers can also get infections like Pseudomonas. “They basically just come from soil, or some people carry Pseudomonas,” he explained. “If it enters the ear, you can get serious ear infection.”

And just like crowded beaches, pools with too many users present a greater risk of infection from E. coli, according to Hancock.

“Beaches have the advantage of containing very salty water, and you may or may not know that salty water is used to try to treat certain infections in young infants,” he added. “Salty water can be beneficial.”

Hancock has one piece of advice for those who feel discomfort after having gone swimming, even days later. “If you have diarrhea or stomach pain”¦I think that then you’d want to see a physician,” he said.

Stan Bertold is the superintendent of environmental monitoring in Metro Vancouver’s operations and maintenance department. Bertold indicated that his group does not specifically test for particular organisms like E. coli, Giardia, Cryptosporidium, Shigella, and Salmonella.

“The testing that we do is we use a microbiological indicator of fecal contamination, and we monitor for fecal coliforms,” Bertold told the Straight by phone. “That is an indicator organism to show the possible presence of other pathogenic organisms. So that is the appropriate way that we monitor as directed by the health authority.”

Health Canada guidelines establish a limit of no more than 200 coliform bacteria per 100 millilitres for recreational waters.

“Currently this summer, all beaches meet the guidelines for primary-contact recreation, and by primary-contact recreation we mean those are the types of activities that involve people that swim, windsurf, and water ski,” Bertold said on July 16.

In 2009, all recreational waters in Metro Vancouver met the quality guideline except for a few days in Sasamat Lake, where goose droppings were suspected to be the source of high fecal contamination. Metro staff tests waters weekly from May to October. Samples are analyzed at the regional district’s water-quality lab.

The Vancouver Coastal Health Authority posts coliform counts at its Web site.