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Jul 24

Sewage plant linked to Grand Canyon virus


SALT LAKE CITY -- A virus blamed for making more than 130 Grand Canyon rafters and hikers sick this summer has been found in water flowing into the Colorado River from the sewage treatment plant inside Glen Canyon Dam.

Reports of the canyon illness began in June. The victims reported nausea, vomiting and diarrhea. A Norwalk-like virus was identified as the cause, and health officials began testing for the virus at several points along the river.

Preliminary findings from an outbreak investigation report released Wednesday attributed the illness to Norwalk virus.

"We looked at genetic material in a river water sample from Lee's Ferry and a sample of water emitted from the sewage treatment plant that serves the visitor center at the dam, and both tested positive for Norwalk," Chuck Higgins, regional public health consultant for the National Park Service in Denver, told The Salt Lake Tribune.

"Recent work indicates Norwalk may be somewhat resistant to chlorine, and if we find Norwalk is surviving standard sewage treatment, that could have national implications," he said.

Researchers from the Park Service, the Centers for Disease Control and Prevention, and the state of Arizona are breaking down the genetic code of the viral strains found in the river and in the treated wastewater to see if they match.

The outbreak affected river runners on at least 17 river trips. All infected runners used river water as their primary drinking water source, treating it with on-board filtration devices. Most cleaned their water filters on a daily basis, indicating filters may be contaminated by the virus when handled by infected staff or passengers.

Grand Canyon National Park officials will meet with commercial river guides on Saturday to discuss the report and emphasize the need for enhanced water purification and hygiene practices. Park spokeswoman Maureen Oltrogge said an educational program also is planned for noncommercial float trips.

"Because this virus has no other animal hosts than people, we probably have a good chance of finding the source and eliminating it," said Higgins. "But this is a big, long open body of water and we are now developing a research agenda. There's probably 12 dissertations here."