Why Are Hundreds of Grand Canyon Tourists Suddenly Getting Sick?

While hiking in Grand Canyon National Park, Kristi Key came across a concerning site: four hikers resting on the side of the trail, looking a little worse for wear. After learning that two of the hikers had spent the previous night violently vomiting, Key offered to call a rescue team, but the group declined. But when she saw them sitting in the same spot on her return trip, with one of the hikers still spewing chunks, she knew it was time to call for help.

Eventually, a chopper showed up,...