Research Protocol - Elevation and cholera: an epidemiological spatial analysis of the cholera epidemic in Harare, Zimbabwe, 2008-2009

Hdl Handle:
http://hdl.handle.net/10144/618752
Title:
Research Protocol - Elevation and cholera: an epidemiological spatial analysis of the cholera epidemic in Harare, Zimbabwe, 2008-2009
Authors:
Fernandez, M; Schomaker, Michael; Mason, Peter R; Fesselet, Jean François; Baudot, Yves; Boulle, Andrew; Maes, Peter
Abstract:
Background In highly populated African urban areas where access to clean water is a challenge, water source contamination is one of the most cited risk factors in a cholera epidemic. During the rainy season, where there is either no sewage disposal or working sewer system, runoff of rains follows the slopes and gets into the lower parts of towns where shallow wells could easily become contaminated by excretes. In cholera endemic areas, spatial information about topographical elevation could help to guide preventive interventions. This study aims to analyze the association between topographic elevation and the distribution of cholera cases in Harare during the cholera epidemic in 2008 and 2009. Methods We developed an ecological study using secondary data. First, we described attack rates by suburb and then calculated rate ratios using whole Harare as reference. We illustrated the average elevation and cholera cases by suburbs using geographical information. Finally, we estimated a generalized linear mixed model (under the assumption of a Poisson distribution) with an Empirical Bayesian approach to model the relation between the risk of cholera and the elevation in meters in Harare. We used a random intercept to allow for spatial correlation of neighboring suburbs. Results This study identifies a spatial pattern of the distribution of cholera cases in the Harare epidemic, characterized by a lower cholera risk in the highest elevation suburbs of Harare. The generalized linear mixed model showed that for each 100 meters of increase in the topographical elevation, the cholera risk was 30% lower with a rate ratio of 0.70 (95% confidence interval=0.66-0.76). Sensitivity analysis confirmed the risk reduction with an overall estimate of the rate ratio between 20% and 40%. Conclusion This study highlights the importance of considering topographical elevation as a geographical and environmental risk factor in order to plan cholera preventive activities linked with water and sanitation in endemic areas. Furthermore, elevation information, among other risk factors, could help to spatially orientate cholera control interventions during an epidemic.
Affiliation:
Centre of Infectious Disease Epidemiology and Research (CIDER), University of Cape Town; Biomedical Research & Training Institute and the University of Zimbabwe College of Health Sciences; MSF Amsterdam; NADAR sprl, Geographic Information Systems; MSF Brussels
Issue Date:
18-Jun-2012
URI:
http://hdl.handle.net/10144/618752
Language:
en
Appears in Collections:
MSF Research Protocols

Full metadata record

DC FieldValue Language
dc.contributor.authorFernandez, Men
dc.contributor.authorSchomaker, Michaelen
dc.contributor.authorMason, Peter Ren
dc.contributor.authorFesselet, Jean Françoisen
dc.contributor.authorBaudot, Yvesen
dc.contributor.authorBoulle, Andrewen
dc.contributor.authorMaes, Peteren
dc.date.accessioned2017-01-13T11:31:35Z-
dc.date.available2017-01-13T11:31:35Z-
dc.date.issued2012-06-18-
dc.identifier.urihttp://hdl.handle.net/10144/618752-
dc.description.abstractBackground In highly populated African urban areas where access to clean water is a challenge, water source contamination is one of the most cited risk factors in a cholera epidemic. During the rainy season, where there is either no sewage disposal or working sewer system, runoff of rains follows the slopes and gets into the lower parts of towns where shallow wells could easily become contaminated by excretes. In cholera endemic areas, spatial information about topographical elevation could help to guide preventive interventions. This study aims to analyze the association between topographic elevation and the distribution of cholera cases in Harare during the cholera epidemic in 2008 and 2009. Methods We developed an ecological study using secondary data. First, we described attack rates by suburb and then calculated rate ratios using whole Harare as reference. We illustrated the average elevation and cholera cases by suburbs using geographical information. Finally, we estimated a generalized linear mixed model (under the assumption of a Poisson distribution) with an Empirical Bayesian approach to model the relation between the risk of cholera and the elevation in meters in Harare. We used a random intercept to allow for spatial correlation of neighboring suburbs. Results This study identifies a spatial pattern of the distribution of cholera cases in the Harare epidemic, characterized by a lower cholera risk in the highest elevation suburbs of Harare. The generalized linear mixed model showed that for each 100 meters of increase in the topographical elevation, the cholera risk was 30% lower with a rate ratio of 0.70 (95% confidence interval=0.66-0.76). Sensitivity analysis confirmed the risk reduction with an overall estimate of the rate ratio between 20% and 40%. Conclusion This study highlights the importance of considering topographical elevation as a geographical and environmental risk factor in order to plan cholera preventive activities linked with water and sanitation in endemic areas. Furthermore, elevation information, among other risk factors, could help to spatially orientate cholera control interventions during an epidemic.en
dc.language.isoenen
dc.titleResearch Protocol - Elevation and cholera: an epidemiological spatial analysis of the cholera epidemic in Harare, Zimbabwe, 2008-2009en
dc.contributor.departmentCentre of Infectious Disease Epidemiology and Research (CIDER), University of Cape Town; Biomedical Research & Training Institute and the University of Zimbabwe College of Health Sciences; MSF Amsterdam; NADAR sprl, Geographic Information Systems; MSF Brusselsen
All Items in MSF are protected by copyright, with all rights reserved, unless otherwise indicated.