A popular hotel pool in Washington state has been linked to an outbreak of a highly contagious parasite that sickened 14 people, health officials say.
The illnesses were connected to the swimming pool at McMenamins Anderson School in Bothell, about 20 miles northeast of Seattle.
The property is a former 1931 junior high school that was converted into a sprawling hotel and entertainment complex.
According to King County Public Health, all 14 people who became sick had spent time in the pool on Aug. 29 or Aug. 30.
Their symptoms included diarrhea, nausea, stomach cramps and fever.
The first illnesses began appearing several days later, between Sept. 3 and Sept. 5.
Health officials ultimately linked the outbreak to cryptosporidiosis, an intestinal illness caused by the microscopic parasite Cryptosporidium, commonly known as Crypto.
Four of five people who underwent laboratory testing tested positive for the parasite.
Fortunately, no hospitalizations or deaths were reported.
Investigators believe an infected person likely entered the pool and unknowingly contaminated the water.
Crypto spreads through fecal matter and can infect swimmers if they swallow even a small amount of contaminated water.
What makes the parasite particularly troublesome is its resistance to chlorine.
Unlike many germs that are killed quickly in properly treated swimming pools, Cryptosporidium can remain alive in chlorinated water for more than a week.
That means even a pool that appears clean and is being properly maintained can still potentially spread the illness after contamination.
King County investigators interviewed six people who became sick and inspected the pool facility on Sept. 21.
Inspectors found no health or safety violations.
They also reviewed the facility’s records and found no documented fecal incidents in the pool on Aug. 29 or during the previous 10 days.
Public health officials said the pool was well maintained and that the facility had been following county safety requirements.
The investigation therefore did not find evidence that poor pool maintenance caused the outbreak.
Cryptosporidiosis most commonly causes frequent, watery diarrhea.
Other symptoms can include stomach cramps, nausea, vomiting, fever, dehydration and weight loss.
Symptoms usually begin between two and 10 days after exposure and can continue for several weeks.
Most otherwise healthy people recover without serious complications, but the illness can be more dangerous for people with weakened immune systems.
The parasite can also continue spreading after someone starts feeling better.
Because of that, health officials recommend that anyone who has had diarrhea stay out of swimming pools for at least two weeks after symptoms stop.
That advice is especially important with Crypto because the parasite can continue being shed in stool even after a person feels healthy again.
Officials also recommend showering with soap before entering a pool and avoiding swallowing pool water.
King County Public Health said the outbreak now appears to be over and has closed its investigation.
Officials reviewed proper sanitation procedures with the pool operator and reminded staff that guests should not enter the water if they have experienced vomiting or diarrhea during the previous two weeks.
The episode serves as an unusual reminder that clear, properly chlorinated pool water does not necessarily mean every possible germ has been eliminated.
In this case, investigators found the facility was following the rules, but one particularly stubborn parasite was still able to leave more than a dozen swimmers sick.
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