The 131st Annual Meeting (November 15-19, 2003) of APHA

Abstract #73377

Ami S. Patel, MPH, Department of Epidemiology, University of Pittsburgh Graduate School of Public Health, 127 Parran Hall, 130 DeSoto St, Pittsburgh, PA 15261, (412) 624-6170, patela@edc.pitt.edu

In June, 2002 an outbreak of acute gastroenteritis occurred among Colorado River rafters within Grand Canyon National Park. Investigators from federal and state agencies were called to determine the agent, source, and extent of the outbreak. A systems based approach was used to coordinate an environmental assessment with traditional epidemiologic and laboratory methods.

Preliminary environmental and epidemiological assessments, including water and stool sample collection, were made during a site visit. Rafting trips that departed between May 24 and June 8, 2002 comprised the trip cohort (N=42). Environmental health practice information and trip histories were collected via questionnaire. A retrospective rafter cohort (N=201) was also established to identify risk factors associated with illness.

Statistical differences in activities, camp locations, food sources and preparation, and waste management were not noted between sick and well trips or rafters. However, trips utilizing ceramic cartridge filters without additional disinfection techniques were more susceptible to illness (RR=11.2, p=0.005). Water samples and two of the seven individual stool specimens tested positive for multiple genetic sequences of Norovirus.

Results of this investigation are most consistent with Norovirus as the agent and river water as the primary source of transmission. Deficiencies in the “system” can be attributed to improper processing of drinking water. Recommendations issued to the National Park Service included standard disinfection and water collection protocols and more frequent filter maintenance among others. Future research such as environmental assessment of sewage discharges to the Colorado River and continued epidemiological surveillance is suggested.

Learning Objectives:

At the conclusion of this session the participant should be able to:
• Recognize the necessity for multidisciplinary collaboration in outbreak investigations.
• Understand the utility of a systems-based approach in public health assessments.
• Discuss recommendations for continued environmental and epidemiologic surveillance and additional strategies for prevention of future viral outbreaks among river rafters.

Keywords: Environmental Health,

Presenting author's disclosure statement:
I do not have any significant financial interest/arrangement or affiliation with any organization/institution whose products or services are being discussed in this session.