MORE than a hundred hikers have fallen ill in the Grand Canyon since May due to highly contagious norovirus, according to health officials.
"It is unknown at this time what the source of the illness is," the National Park Service Office of Public Health said in a statement.
Health officials say the 118 infections have spanned 16 different trips in the Grand Canyon and Colorado River backcountry, with the most recent case reported on June 2.
"We have plateaued a little bit in terms of the number of reported cases, especially over the last three to four weeks," Joelle Baird, a public affairs specialist at the Grand Canyon National Park, told NBC.
One case on May 15, involved a helicopter rescue and was documented by a hiker on Facebook.
Krisiti Key, of Prescott, Arizona was hiking the canyon when she saw two hikers "violently ill" with no water.
After she found out that one of the hikers in the group had been vomiting the night before, she offered to call emergency services for help. They declined her offer, so she kept on her trail.
When she found them on her way back, she decided to call for help since one of them was still vomiting. A helicopter came three hours later to their rescue.
"Everyone was safe and rested," Key wrote, "But, come to find out, the healthy Hiker was now in his room throwing up,"
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"Several rescues happened on the same trail that same week for the exact same thing," Key continued.
Jan Balsom, Chief of Communications at the Office of the Superintendent at Grand Canyon National Park, said alerts have been issued about the norovirus since May 20.
"We haven't seen something like this kind of outbreak in about 10 years," Balsom told the Daily Beast.
Balsom said, officials "have been following up with interviews from participants from trips who have gotten sick,"
"They've been testing poop scans to try to determine whether or not it is noro."
Detecting norovirus in stool samples is hard to do since there is a limited window of time to find the norovirus in the sample, according to Balsom.
This illness causes vomiting, diarrhea, cramping, body aches, and a mild fever. It is spread through close contact with someone with the virus, touching a contaminated surface, or contaminated food and water.
Hikers have been advised to not drink out of communal water sources, practice proper hand washing, and boil or chemically disinfect their drinking water.
A public health team made up of the Grand Canyon National Park, the Arizona Department of Health, the CDC, and others are working to address this outbreak.