Could the Seine Be Making Olympic Athletes Sick? We Asked an Expert

Paris city officials swear the Seine is safe for swimming, but that hasn't stopped athletes at the Paris Olympics from getting sick after taking a dip in the renown river. Despite the amount of ongoing pollution in the Seine, Olympic triathletes ended up competing in the (suspiciously?) green waters, after the bacteria levels were deemed "acceptable" by officials. Now, in a not-so-shocking turn of events, multiple Olympians have fallen ill.

Norway's Vetle Bergsvik Thorn, for instance, reportedly had a "bad stomach illness" after competing in the river, per AP News, although he's unsure whether this was caused by the Seine or food poisoning. Likewise, just three days after competing in the women's triathlon, Swedish athlete Tilda Månsson got sick, along with triathlete Adrien Briffod, who developed a stomach infection after swimming in the Seine. Belgium even ended up withdrawing from the mixed relay triathlon due to triathlete Claire Michel falling ill post-swimming in the Seine.

Paris organizers have since urged people not to jump to conclusions, saying plenty of athletes have gotten sick without swimming in the Seine (although this isn't entirely reassuring), so it's too soon to say that the Seine is causing these symptoms. But as Swedish Olympic Committee spokesman Lars Markusson told Swedish broadcaster SVT, "Since others have also become ill, perhaps you don't need to be a doctor to draw the conclusion that it had to do with the swimming in the Seine."

In light of all the poop protests and sick athletes, we've been thinking more and more about the consequences of swimming in poopy water. Now that the athletes have officially taken the plunge, we asked an infectious disease expert to explain what happens if you swim in poop (and as turns out, more of us than you might think may have done exactly that).

Amesh A. Adalja, MD, is a senior scholar at the Johns Hopkins Center for Health Security whose research focuses on biosecurity and emerging infectious diseases.

Whether or not it's safe to swim in the Seine has been a topic of conversation since before the Games even started. In preparation for open-water events at the Olympics, the French government spent over $1.5 billion trying to make the Seine swimmable. When it seemed like they weren't succeeding, Parisians threatened to protest the endeavor by . . . well . . . pooping in the river. This included a viral website and corresponding hashtag reading #JeChieDansLaSeineLe23Juin (I shit in the Seine on June 23).

Then on July 17, Anne Hidalgo, the mayor of Paris, braved the Seine to prove it was safe for Olympic athletes to compete in. It's hard not to respect the dedication, but given that a June 21 analysis found two kinds of fecal bacteria in the Seine (even before Parisians threatened to poop in the river), the demonstration wasn't entirely convincing.

Much like the Seine, the answer is a bit murky. "Water is never sterile. There are millions upon millions of bacteria, viruses, and other microbes present," says Amesh A. Adalja, MD. "The key thing is making sure that the levels are not representative of major fecal contamination, which could lead to human illness."

It's unclear whether or not Parisians really followed up on their poopy plans for protest, but considering that rain often causes the sewers to overflow into the Seine, it's possible that it wouldn't have made a tremendous difference if they did. Swimming in the Seine was originally banned in 1923 due to pollution, and while the French government may want us to believe it's changed, city testing found unacceptable levels of E. coli on the majority of days between June 3 and July 2.

Unfortunately, this isn't just a Paris problem.

In 2022, Environment America found that 1,761 out of 3,192 beaches in the US (55 percent) reached potentially unsafe levels of fecal contamination on at least one of the days they were tested. More recently, the Surfrider Foundation's 2023 Clean Water Report found that out of 9,538 water test results, 67 percent indicated low bacteria levels, 11 percent indicated medium bacteria levels, and 22 percent measured high bacteria levels that exceeded state standards for recreational waters. The Foundation also noted that at least one high bacteria result was found in 64 percent of the 567 beaches tested, pointing to sewage spills and inadequate infrastructure as some possible contributors to this pollution. (They didn't specify what type of bacteria they found, but the report did note that, "Sewage spills and infrastructure failures release over 900 billion gallons of untreated sewage into surface waters every year," so do with that what you will.)

Given these numbers, it's worth asking — what happens if you do swim in poop? "Bacterial levels in swimming water are more [of a] surrogate for fecal contamination occurring," Dr. Adalja explains. "This confers a risk, not only of getting bacterial infections such as E. coli, but all sorts of pathogens, such as norovirus." That's not to mention the GI issues that could occur if water is swallowed (stomach cramps, vomiting, diarrhea), or the complications of an open wound becoming infected.

If you're worried you might be swimming in contaminated water (Olympic athletes, listen up), Dr. Adalja recommends cleaning any open cuts or abrasions and applying antibiotic ointment to avoid infection. He also points out that most swimming areas in lakes or rivers post fecal coliform counts, which can help you see how contaminated they really are. You don't need to expose yourself to small amounts of E. coli, as triathlete Seth Rider claimed to do (even skipping hand-washing in an effort to build immunity).

In the meantime? Sorry to Paris officials, but it's probably best to stay out of the Seine.

Chandler Plante is an assistant editor for PS Health & Fitness. Previously, she worked as an editorial assistant for People magazine and contributed to Ladygunn, Millie, and Bustle Digital Group. In her free time, she overshares on the internet, creating content about chronic illness, beauty, and disability.