Printed on: September 06, 2013

Illnesses on river continue


SALMON -- Bouts of vomiting and diarrhea afflicting some boaters on the Middle Fork of the Salmon River continue to be reported to Idaho health officials more than a month after the suspected norovirus outbreak began.

Nine boaters, including members of a private float group and U.S. Forest Service officials patrolling the river, contracted the highly contagious virus last week, bringing to more than 100 the number of rafters who have been stricken this summer, said Mike Taylor, Eastern Idaho Public Health District surveillance epidemiologist.

State health officials first were notified at the end of July that some boaters on the wild and scenic stretch of river in the Frank Church River of No Return Wilderness were suffering from severe diarrhea and violent vomiting that lasted from 24 to 72 hours.

Scientists strongly suspected norovirus, and later tests confirmed that suspicion, as well as isolated cases of the waterborne parasite giardia and E. coli bacterial infections.

Health experts advised stepped-up hygiene practices, including frequent hand washing. U.S. Forest Service officials advised private and commercial boaters to take those precautions even before they launched. Outfitters and rafters have been diligent about those measures, leading Taylor to believe they have helped stem, but not stop, the illness.

Findings from a survey of 434 boaters showed that 105, or almost 25 percent, reported bouts of vomiting or diarrhea before, during or after their trips on the Middle Fork, Taylor said. Roughly 81 percent of those who responded to the survey were private boaters, and 19 percent were commercial.

The object for health and forest officials is to identify the sources of transmission and learn as much about the outbreak as possible in order to prevent it in future years. The Middle Fork's world-class rapids draw thousands each season to Salmon and surrounding communities, fueling local economies that depend on outdoor recreation.

Taylor said investigation into the outbreak has broadened to include Salmon, Challis and Stanley to determine whether the spike may be linked to public places frequented either before or after float trips.

"We don't want to put a damper on fun in the outdoors," he said. "We want people to enjoy that and to be healthy and safe at the same time."

So far, findings from the boater survey show that the suspected norovirus outbreak does not discriminate by age or gender. But scientists have observed a possible association with filtering of water, since a number of those who were sickened drank water that had been filtered.

Taylor said questions raised by that possible link include whether the filters were being used properly and whether the water came from the river, a creek or a spring.

It was possible, he said, that health officials may not be able to pinpoint the exact causes and sources of transmission of this season's outbreak, which likely will wind down with the end of the rafting season.

"We're trying to look at all aspects and come up with enough answers to avoid these kinds of spikes," Taylor said.