Effects of sewerage on diarrhoea and enteric infections: a systematic review and meta-analysis
Abstract
Background Sanitation is inadequate in most cities in developing countries, with major effects on infectious disease burden: in this situation, is piped sewerage an appropriate solution, or should efforts focus on systems based on onsite solutions, such as latrines? We reviewed the effects of the presence of sewerage systems on diarrhoeal disease and related outcomes. We included only observational studies because so far there have been no randomised controlled trials.Methods We identified relevant studies by use of a comprehensive strategy including searches of Medline and other databases from 1966 to February, 2010. In studies that compared sewerage with one other sanitation category, we used relative risk (RR) estimates for sewerage versus the other category. When a single study made two or more comparisons, we calculated a weighted average RR value, and used this value in our meta-analysis. We used the most adjusted RR estimate provided by the authors; if no adjusted estimate was available, we used the crude estimate. To obtain pooled-effect estimates, meta-analyses were done by use of an inverse variance method-ie, the study-specific adjusted log ORs for case-control and cross-sectional studies, and log RRs for cohort studies, were weighted by the inverse of their variance to compute a pooled RR with 95% CI.Findings 25 studies investigated the association between sewerage and diarrhoea or related outcomes, including presence of intestinal nematodes. Pooled estimates show that sewerage systems typically reduce diarrhoea incidence by about 30% (RR 0.70, 95% CI 0.61-0.79), or perhaps as much as 60% when starting sanitation conditions are very poor. Studies with objective outcome measures showed even stronger pooled effect than studies that assessed diarrhoea incidence with interviews, while sensitivity analysis indicated that the effect remains even if we assume strong residual confounding.Interpretation Sewerage interventions seem to reduce the incidence of diarrhoea and related outcomes. However, we urge cautious interpretation of these findings, because, in many contexts, sewerage might be less cost effective and sustainable than onsite alternatives.Funding None.
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A systematic review focusing on the effects of sewerage on incidence of diarrhoea included intervention and non-intervention studies, and searched the literature from Jan 1, 1966, to Feb 28, 2010.
“A systematic review focusing on the effects of sewerage on incidence of diarrhoea included intervention and non-intervention studies, and searched the literature from Jan 1, 1966, to Feb 28, 2010.14”
A systematic review found an overall RR of 0·70 (0·61-0·79) for all sewer studies and of 0·41 (0·27-0·61) when sanitation service level at baseline or in the comparison group was very poor.
“A systematic review looking specifically at the association between sewer connection and risk of diarrhoea found an overall RR of 0·70 (0·61–0·79) for all sewer studies and of 0·41 (0·27–0·61) when sanitation service level at baseline or in the comparison group was very poor.14”
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- Authors
- Norman, G., Pedley, S., & Takkouche, B.
- Affiliations
- University of Surrey (GB)
- Universidade de Santiago de Compostela (ES)
- Corresponding author
- Norman, Guy
- ORCID
- Takkouche, Bahi
- Venue
- The Lancet Infectious Diseases
- Publisher
- Elsevier BV
- Published
- 2010-08
- Volume
- 10
- Issue
- 8
- Pages
- 536-544
- ISSN
- 1473-3099 (ISSN-L)
- OpenAlex
- W2159218216
- Cited by
- 115
- References
- 58
- Citations by year
- 2026: 2 · 2025: 6 · 2024: 4 · 2023: 6 · 2022: 11 · 2021: 12 · 2020: 8 · 2019: 6 · 2018: 11 · 2017: 8 · 2016: 7 · 2015: 8 · 2014: 11 · 2013: 5 · 2012: 5
- FWCI
- 0.50
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- The Lancet Infectious Diseases (publishedVersion)
- PubMed (publishedVersion)
- Open Research (University of Surrey) (submittedVersion)
- DIGITAL.CSIC (Spanish National Research Council (CSIC)) (submittedVersion)
- Surrey Research Insight Open Access (The University of Surrey) (submittedVersion)
- Topics
- Health Sciences › Nursing › Nutrition and Dietetics › Child Nutrition and Water Access
- Physical Sciences › Environmental Science › Health, Toxicology and Mutagenesis › Public Health and Environmental Issues
- Physical Sciences › Environmental Science › Water Science and Technology › Fecal contamination and water quality
- Keywords
- sewerage, diarrhea, gastrointestinal infections, sanitation, latrines, on-site sanitation, intestinal nematodes, sanitation interventions, developing countries
- MeSH terms
- Diarrhea, Humans, Intestinal Diseases, Parasitic, Sanitation, Sewage
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