Two river-running companies have reported trips in the Grand Canyon characterized by nausea, vomiting and diarrhea -- the typical hallmarks of norovirus.
A boating trip leaving the river on June 7 said all but two of its crew were hit.
Another company reported some of the same symptoms in May.
Coconino County health workers are sampling latrines and other waste for norovirus (results aren't in yet).
Boaters are emailing one another warnings to be diligent in purifying water and having all aboard wash hands.
Norovirus has visited Grand Canyon and Flagstaff repeatedly in past years, which isn't surprising for travel destinations and a virus that spreads quite easily.
It is characterized by a day or two of vomiting and/or diarrhea, sometimes fevers and aches, and it infects about 21 million annually in the United States.
Sometimes considered food poisoning or the flu (the flu is caused by a different virus), the norovirus can live for a week on surfaces and survive temperatures up to 140 degrees, according to information from the Centers for Disease Control and Prevention.
SHARING CLOSE QUARTERS
Keeping the virus from spreading on a rafting boat where everyone is sharing the same surfaces, bathrooms and space, can be difficult, even in the many cases where guides press passengers to wash hands, segregate sick from ill and prevent ill people from preparing food.
"We have seen norovirus about every year since I've been here," said David Wong, a doctor and medical epidemiologist for the National Park Service, overseeing Grand Canyon.
He said he thinks one or two passengers harboring the illness became a likely source of transmission for each of the rafting parties this year.
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Once on a rafting trip on the Colorado River in Grand Canyon, it's close to impossible to absolutely quarantine a boater, he said, among other sanitation challenges.
"It's very difficult to have good hygiene," Wong said. "People have close quarters. They're sharing the same bathroom facilities."
Dehydration is the most common problem norovirus causes.
HISTORY OF LOCAL OUTBREAKS
Flagstaff's Mountain School reported an estimated 70 cases of norovirus symptoms among students and staff in May.
Along the Colorado River through Grand Canyon, some 23 boaters reported similar symptoms in 2006. An estimated 100 boaters fell ill on the Colorado in the summer of 2005.
A wrestling camp at Northern Arizona University infected 115 with norovirus that same year, requiring disinfecting at Cline Library, the Skydome, dining halls and three dorms after wrestlers ignored instructions to avoid public contact. The Arizona Cardinals summer football camp was moved to Prescott as a precaution.
More than 130 people were reported ill in 2002 after or while rafting the Colorado River through Grand Canyon.
Epidemiologists believed the virus was possibly brought onto the river that year by ill passengers or that a sewage treatment plant at Glen Canyon Dam was a source, due to the high numbers ill. The epidemiologists didn't reach a certain conclusion.
The Centers for Disease Control investigated in 1994, after about 100 river rafters became ill.
Cyndy Cole can be reached at 913-8607 or at firstname.lastname@example.org.