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COORDINATING ENVIRONMENTAL PUBLIC HEALTH PRACTICE WITH EPIDEMIOLOGY AND LABORATORY ANALYSIS: A WATERBORNE OUTBREAK OF SNOW MOUNTAIN VIRUS IN THE BIG HORN MOUNTAINS OF WYOMING
Citation:
Seys, S. A., H. M. Mainzer, A. G. Heryford, A. D. Anderson, G S. Fout, J. P. Sarisky, V. Musgrave, AND K. J. Musgrave. COORDINATING ENVIRONMENTAL PUBLIC HEALTH PRACTICE WITH EPIDEMIOLOGY AND LABORATORY ANALYSIS: A WATERBORNE OUTBREAK OF SNOW MOUNTAIN VIRUS IN THE BIG HORN MOUNTAINS OF WYOMING. Presented at International Conference on Emerging Infectious Diseases, Atlanta, GA, March 24-27, 2002.
Impact/Purpose:
Overarching Objectives and Links to Multi-Year Planning
This task directly supports the 2003 Drinking Water Research Program Multi-Year Plan's long term goal 1 for "regulated contaminants" and long term goal 2 for "unregulated contaminants and innovative approaches" under GRPA Goal 2 (Clean and Safe Water). The overarching objective is to provide the Office of Water, Agency risk assessors and managers, academics, the scientific community, state regulators, water industry and industry spokes-groups the methods they need to measure occurrence of waterborne viral pathogens. The methods developed will improve the quality of risk-based assessments and tools used by the Agency to set regulations, policies and priorities for protecting human health and will allow the Agency to assure the public that the appropriate methods are being used to demonstrate that drinking water is safe from pathogenic agents.
Specific Subtask Objectives:
o Evaluate techniques for enhancement of growth of human enteric viruses in support of CCL #2 and #3 and for use in the UCMR (Subtask A; to be completed by 9/05 in support of LTG 2)
o Develop a multiplex RT-PCR method that incorporates internal controls for use in the UCMR (Subtask B; completed 9/03 in support of LTG 2)
o Develop and evaluate new molecular technologies for use in the UCMR. Included will be real-time RT-PCR methods for Norwalk virus and astroviruses, and integrated cell culture/molecular procedures for detection of infectious viruses (Subtask B; to be completed by 9/05 in support of LTG 2)
Description:
Background: In February 2001, the Wyoming Department of Health received reports of acute gastroenteritis among persons who had recently been on a snowmobiling vacation in the Big Horn Mountains. Initial interviews and laboratory testing suggested that exposure to a calicivirus in drinking water from a lodge was responsible for the illness.
Methods: Environmental health specialists and epidemiologists from several state and federal agencies coordinated an investigation of environmental risk factors and system failures. The environmental assessment of the three lodges in the area included food service operations, water supply systems, and sewage disposal. A retrospective cohort study was conducted among 82 persons identified from guest registers to identify risk factors associated with illness. Stool and water system samples were collected for laboratory analysis.
Results: Statistical analysis from the retrospective cohort study suggested that illness was associated with water consumption at one lodge (RR=3.3, 95% C.I.=(1.4, 7.7)). A chi-square test for linear trend showed that risk of illness increased significantly with the number of glasses of water consumed (p=0.0003). The consumption of individual food items was not statistically associated with illness. Reverse transcription polymerase chair reaction (RT-PCR) testing on 13 stool samples yielded 8 positives for Norwalk-like virus (NLV) genotype II. Fecal contamination of one of three operating wells was also found and one of the samples tested positive for NLV genotype II. The environmental assessment of the property revealed that an inadequately installed sewage system was delivering effluent into shallow soil with poor filtering capacity. This effluent likely contaminated drinking water of an overloaded water system.
Conclusion: This event represents the largest waterborne outbreak ever reported in Wyoming. It illustrates the potential for waterborne transmission of viral gastroenteritis and the advantages of coordinating environmental public health practice with traditional epidemiologic and laboratory investigations. It is essential that personnel representing each of these entities participate fully in outbreak investigations and that environmental health specialist receive training in systems analysis and sampling methodologies. Outbreak investigations should address all of the systems of a facility including food service, water supply, and sewage systems.