Health workers in northern Arizona were waiting Thursday for test results to confirm whether the flu-like illness known as norovirus has surfaced among boaters in the Grand Canyon.

The Arizona Daily Sun reports Coconino County health officials were investigating facilities along the Colorado River after two river-running companies each described a trip where passengers and crew experienced nausea, vomiting and diarrhea.

One boating trip on June 7 reported all but two of its crew members were taken ill with those symptoms. The other company said people on an excursion in May had the same symptoms.

Trish Lees, a Coconino County Health Services Department spokeswoman, said county workers have taken samples from latrines, restrooms provided by the boating companies as well as waste from sick passengers.

Health officials said keeping the norovirus from spreading on a rafting boat is challenging because passengers are sharing the same space and surfaces. David Wong, a doctor and medical epidemiologist for the National Park Service, overseeing Grand Canyon, said one or two infected passengers could easily have led to the virus being transmitted to others.

"It’s very difficult to have good hygiene," Wong said. "People have close quarters. They’re sharing the same bathroom facilities."

In the summer of 2005, nearly 100 boaters became sick on the Colorado River, according to officials. That same year, 115 people attending a wrestling camp at Northern Arizona University also came down with the virus. As a result, several campus facilities had to be disinfected after wrestlers disregarded instructions to avoid public contact. The Arizona Cardinals relocated their training camp to Prescott as a precaution.