文章基本信息

标题：Integrating Disease Control Strategies: Balancing Water Sanitation and Hygiene Interventions to Reduce Diarrheal Disease Burden
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作者：Joseph N.S. Eisenberg ; James C. Scott ; Travis Porco 等
期刊名称：American journal of public health
印刷版ISSN：0090-0036
出版年度：2007
卷号：97
期号：5
页码：846-852
DOI：10.2105/AJPH.2006.086207
语种：English
出版社：American Public Health Association
摘要：Objectives. Although the burden of diarrheal disease resulting from inadequate water quality, sanitation practices, and hygiene remains high, there is little understanding of the integration of these environmental control strategies. We tested a modeling framework designed to capture the interdependent transmission pathways of enteric pathogens. Methods. We developed a household-level stochastic model accounting for 5 different transmission pathways. We estimated disease preventable through water treatment by comparing 2 scenarios: all households fully exposed to contaminated drinking water and all households receiving the water quality intervention. Results. We found that the benefits of a water quality intervention depend on sanitation and hygiene conditions. When sanitation conditions are poor, water quality improvements may have minimal impact regardless of amount of water contamination. If each transmission pathway alone is sufficient to maintain diarrheal disease, single-pathway interventions will have minimal benefit, and ultimately an intervention will be successful only if all sufficient pathways are eliminated. However, when 1 pathway is critical to maintaining the disease, public health efforts should focus on this critical pathway. Conclusions. Our findings provide guidance in understanding how to best reduce and eliminate diarrheal disease through integrated control strategies. In the developing world, more than 1 billion people continue to lack an adequate supply of clean water and adequate disposal of excreta. 1 Such statistics explain why the overall global burden of water-, sanitation-, and hygiene-related disease remains high 2 ^, 3 even though oral rehydration therapy has led to reductions in mortality. 4 Despite this demonstrated need for water, sanitation, and hygiene improvements, 3 our understanding of integrated control strategies remains poor. Part of the reason is that most intervention studies have examined 1 intervention in isolation without considering other potential pathways of transmission. There is increasing evidence that the efficacy of household water quality interventions depends on the level of sanitation within the targeted community. 5 ^– 7 This dependency may explain why, although many household-level water quality intervention studies have shown impressive reductions in health burden, 8 results have been highly variable. Some studies have shown reductions as high as 85%, and others have shown no reduction. Moreover, estimates of disease reduction may be inflated because of publication bias (positive results are more likely to be published than are negative results), lack of blinding (a study design feature in which participants do not know whether they are involved in the intervention or nonintervention arm of the study; only 1 of the 15 developing country studies reviewed by Fewtrell et al. 8 were blinded), and lack of randomization (only 5 of the 15 studies reviewed by Fewtrell et al. 8 were randomized). 9 These interpretive challenges arise in part because enteric pathogens are transmitted through a complex set of interdependent pathways, including both contaminated food and water along with household- and community-level person-to-person routes; these various pathways have been codified in the F diagram, which classifies transmission pathways as mediated through food, fingers, fomites, flies, and so on 10 (see Bern et al., 11 Huttly et al., 12 and Curtis et al. 13 for reviews). The exposure factors summarized in the F diagram (e.g., general hygiene behaviors, 14 ^, 15 fecal contamination, 16 ^– 18 food contamination, 19 and drinking water storage practices 19 ) as well as more distal factors (e.g., day-care centers 20 and socioeconomic factors 21 ^, 22 ) are important to our understanding of these pathways. Water may be contaminated through runoff and may expose individuals through drinking water or recreational, bathing, or washing activities, and food may be contaminated either through infected animals or from contact with contaminated water or soil. Inadequate hygiene may result in contamination of fomites in common living spaces 23 ; infection may then be transmitted in many ways (e.g., through exposures in day-care centers or through sexual activity). Soil may be contaminated through improper management of excreta (poor sanitation). Cairncross et al. 24 extended the F diagram by differentiating between infection transmission within households and within the public domain. Other studies have addressed the interaction between different transmission pathways, suggesting that the risk associated with water contamination depends on the level of community sanitation. 5 ^, 7 ^, 25 Although implicitly assuming that level of community sanitation modifies the association between water contamination and diarrheal disease, none of these studies have addressed the observation that the multiple transmission pathways and contagious nature of pathogens result in risks that are dependent on the disease status of the community. 26 ^– 29 Many enteric pathogens can be transmitted from infectious human excreta to susceptible humans either directly or indirectly through the environment, and thus they are sustained through chains of transmission that may pass through combinations of pathways. The importance of each pathway depends on the pathogen and specific environmental conditions, and the efficacy of any given exposure-specific intervention strategy depends on the level of pathogen exposure from other pathways. We used simulation modeling to evaluate the effectiveness of water quality interventions under varying community sanitation and hygiene conditions, explicitly acknowledging that rates of infection depend on numbers of current and past infections. We characterized the specifics of this dependency by explicitly modeling transmission pathways, in effect yielding a dynamic version of the F diagram. Specifically, we determined (1) how the efficacy of water quality interventions depends on the level of both household- and community-level transmission and (2) the conditions under which water quality interventions, hygiene and sanitation improvements, or both are effective in reducing the burden of disease in a community.