Why You Shouldn't Swim in Dutch Canals

Whether you are attending Amsterdam Pride, floating on the canals, or just strolling along Holland's streets on a hot day, let us just say this: No matter how inviting the nearby water looks, don't take a dip! You might end up with more of a souvenir than you intended.

Amsterdam's canals may be contaminated with rat urine. According to a recent report in the New England Journal of Medicine, an 18-year-old man was hospitalized after falling in a Netherlands canal with a severe case of leptospirosis, a bacterial infection that can cause fever, jaundice, hemorrhages (including in eyes) and even kidney failure.

Some are familiar with the impact the bacteria can have on dogs if they come in contact with water or soil contaminated by urine from an infected animal, but human cases are less common. NEJM graphically demonstrated the potential impact in a post on Twitter:

Leptospirosis is caused by a spiral-shaped bacterium Leptospira interrogans, that infects wild and domestic animals (pigs, horses, cows, dogs) and is passed by shedding into an infected animal's urine. It is most dangerous to humans when found in brown rats because of their close proximity to humans. Like dogs, people can become infected through direct contact or through exposure to contaminated water and soil. Once the bacteria gets into the bloodstream it multiplies and attacks the liver and kidneys, which can cause organ failure. It can also attack the brain (and cause meningitis) or the lungs (where it can cause acute respiratory distress).

While L. interrogans is found more frequently in tropical and subtropical regions, it has spread across the globe and The World Health Organization says human-to-human transmission is possible but rare. The Pan American Health Organization notes there are more than 500,000 cases of leptospirosis each year. Only 10 percent of cases are severe, and a fraction of those cases are fatal, according to the Centers for Disease Control and Prevention.

Still, the CDC warns, "The disease has also been associated with swimming, wading, kayaking, and rafting in contaminated lakes and rivers. As such, it is a recreational hazard for campers or those who participate in outdoor sports. The risk is likely greater for those who participate in these activities in tropical or temperate climates."

If you are infected, antibiotics are usually effective. In severe cases, as with the 18-year-old case study, hospitalization and intravenous antibiotics may be needed to resolve the symptoms. The young man reportedly returned to good health within four weeks.