The outbreak of Norwalk virus on cruise ships grabbed
national headlines last fall, but few have heard of the
virus’s untimely arrival on rubber rafts in the depths of the
Grand Canyon. Last summer, Norwalk infected at least 130 Grand
Canyon recreationists, who spent their river trips vomiting and
running for the groover (that’s river-speak for
“toilet”).
Investigators traced the Norwalk
outbreak to the Bureau of Reclamation’s sewage plant inside
Glen Canyon Dam, which treats waste from the visitor’s center
and power plant. Rather than using chlorine, which could kill fish
below the dam, the plant uses ultraviolet light. But “viruses
are more resistant than other organisms to UV light,” says
Dr. Dennis Juranek, senior scientist at the Centers for Disease
Control and Prevention.
Rafters treat their drinking
water with chlorine, but they can’t use enough to kill the
hardy virus without making the water undrinkable. Chuck Higgins, a
public health consultant, will work with raft guides to develop
better filtering procedures. Next season, he says, rafters may have
to increase the dosage of chlorine and then use charcoal filters to
remove the chlorine taste.
As for the sick rafters,
“it sure wasn’t a comfortable time,” says river
guide Mike Denoyer. “But it cleared up and people were able
to enjoy the rest of their trip.”
Barry Wirth of
the Bureau of Reclamation empathizes. “Being sick (with the
Norwalk virus) in your home with your toilet and bottle of aspirin
is one thing, but if you’re on a sandbar and half of your
(rafting) group and the guide is sick, it’s a whole other
situation.”
This article appeared in the print edition of the magazine with the headline Virus attacks in the Grand Canyon.
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