The West Boise YMCA pool was closed Tuesday and Wednesday, after Central District Health determined that a couple of people contracted the parasite cryptosporidiosis after swimming at the pool, an epidemiologist said Thursday.

Hyper-chlorination of the pool is being done to ensure that the parasite is killed, epidemiologist Sarah Correll said. A YMCA official said the pool is crypto-free and open Thursday.

Cryptosporidiosis, commonly known as crypto, is usually spread by accidentally swallowing water that has been contaminated with human stool or animal waste. The most frequent symptom is watery diarrhea with abdominal cramping, which can be accompanied by dehydration, weight loss, abdominal pain, fever, nausea, and vomiting.

The parasite has been plagued Treasure Valley pools this summer. Correll said all public pools in Ada County have had to hyper-chlorinate multiple times. In late September, Southwest District Health Department reported that crypto cases in Canyon County were up ten-fold since August.

Correll said some people suffer from the parasite for just 24 hours, while others are sick for up to three to four weeks. Those who have diarrhea are urged to refrain from swimming for two weeks after their diarrhea stops.

"The pools will continue to get reinfected, if people with diarrhea continue to swim," she said.