Fourteen people got sick after swimming in a hotel pool in Bothell, Washington, in late August, and health officials have traced the outbreak to a parasite that chlorine can’t easily kill.
The illnesses were linked to the pool at McMenamins Anderson School, a 1931 junior high school that was converted into a boutique hotel and entertainment spot about 20 miles north of Seattle. Public Health Seattle and King County investigated after people reported symptoms including diarrhea, stomach cramps, nausea and fever that started days after their visit to the pool.
Five of the people who got sick were tested, and four were confirmed to have Cryptosporidium. It’s a microscopic parasite, often called “crypto,” that lives in the gut and spreads through feces. It causes cryptosporidiosis, an illness known for watery diarrhea that can last for days.
Investigators believe the outbreak started when someone who already had the parasite got into the hotel pool and spread it to other swimmers. Just a small amount of contaminated water swallowed while swimming is enough to make someone sick.
The hotel was not at fault. When the health department inspected the pool on Sept. 21, it found no violations, and officials said the facility was well maintained and followed all county safety rules. The pool’s operator had not recorded any incidents involving fecal matter in the days before the outbreak.
The problem is the parasite itself. Cryptosporidium has a tough outer shell that makes it highly resistant to chlorine, so it can survive for several days even in a properly treated pool. That is why it is one of the most common causes of illness tied to swimming pools and water parks.
No one was hospitalized and no deaths were reported. Health officials say the outbreak appears to be over and the investigation is complete.
Officials are urging swimmers to stay out of pools for at least two weeks after having diarrhea or vomiting, since people can still spread the parasite even after they feel better. Swimmers should also shower with soap before getting in, wash their hands after changing diapers or caring for someone who is sick, and tell pool staff right away if they see feces or anything else in the water that could contaminate it.
