Improving waterborne disease outbreak investigations

Abstract

This article is a summary of discussions held and recommendations made at a workshop for the investigation of waterborne disease outbreaks in Chapel Hill, North Carolina, December 7-8, 1998. Suspected waterborne outbreaks in the United States are primarily investigated by state and local public health officials who may infrequently conduct enteric disease outbreak investigations. Thus, it is important that officials have a formal plan to ensure that epidemiological studies are methodologically sound and that effective collaboration occurs among the epidemiologists, scientists, and engineers who will conduct the investigations. Laboratory support to analyze water samples and clinical specimens should be arranged well in advance of when services may be needed. Enhanced surveillance activities can help officials recognize additional outbreaks and initiate investigations in a timely manner. Epidemiologists should pay more attention early in the investigation to study design, questionnaire development, and sources of bias, especially recall bias, that may affect the interpretation of observed associations. Improved investigations can increase our knowledge about important etiological agents, water systems deficiencies, and sources of water contamination so that waterborne outbreaks can be more effectively prevented.

Published Case Studies of Waterborne Disease Outbreaks—Evidence of a Recurrent Threat

“…Many waterborne outbreaks may go undetected, and, for those outbreaks that are detected, a causative agent is often not identified. A number of suggestions for improved outbreak investigation were made by Craun et al (2001) .…”

“…The approach of analytical epidemiology (case‐control or cohort studies) involves collecting data suitable for statistical analysis to provide a pattern of evidence that others can independently evaluate for strength of association between drinking water exposure and disease, without relying primarily on the interpretations and judgments of the investigators. Unfortunately, there are many practical limitations to analytical studies, including information and recall bias ( Craun et al, 2001 ). The latter has been questioned for the total number of cases that were estimated for the Milwaukee outbreak ( Craun and Frost, 2002 ; Hunter and Syed, 2002 ).…”

Reported waterborne outbreaks of gastrointestinal disease in Australia are predominantly associated with recreational exposure

“…Sensitive waterborne outbreak surveillance systems will remain especially important into the future with the current increase in recycled water use and the likely increase in extreme weather events due to effects of climate change. 24,25 …”

Towards a US national estimate of the risk of endemic waterborne disease – sero-epidemiologic studies

“…Nonetheless, such studies may also yield epidemiologically useful information. The particular importance of antibody studies epidemiologically is that they offer a truer reflection of prevalence than isolation of organisms and/or clinical diagnoses, both of which underestimate true prevalence (Hunter 1997a(Hunter 2000Craun et al 2001;Frost et al 2003a;Priest et al 2005).…”