Tobler said he's heard of the method and "in principle it seems to work," but the system takes hours overnight to take effect.

"The people aren't getting sick overnight," he said. "The sad truth is that most people who get crypto get it because someone right next to them had an accident in the pool."

But Tobler said secondary systems such as flocculation can work in tandem with chlorination to add an extra layer of protection for swimmers. But he recommended pool managers be judicious when they research the products.

"I would do my homework and make sure the product I pick is best for my pool," he said.

Ultimately, Tobler said, the best way people can prevent a future outbreak is to not swim when ill.

"If you are sick and swim," he said, "you will get others sick as well," he said.

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E-mail: jdana@desnews.com