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

BMC Public Health

Research Article

Peter R Mason¹  Michael Schomaker²  Andrew Boulle²  Miguel A Luque Fernandez²  Peter Maes³  Jean F Fesselet⁴  Yves Baudot⁵ 

[1] Biomedical Research & Training Institute and the University of Zimbabwe College of Health Sciences, Harare, Zimbabwe;Centre of Infectious Disease Epidemiology and Research (CIDER), University of Cape Town, Cape Town, South Africa;Medecins sans Frontieres / Medical department: Water, Hygiene and Sanitation Unit, Brussels Operational Centre, Brussel, Belgium;Medecins sans Frontieres / Public health department: Water, Hygiene and Sanitation Unit, Amsterdam Operational Centre, Amsterdam, The Netherlands;NADAR sprl, Geographic Information Systems, Marchin, Belgium;

关键词: Cholera;    Generalize Linear Mixed Model;    Attack Rate;    Average Elevation;    Sewage Disposal;   

DOI  :  10.1186/1471-2458-12-442

 received in 2011-10-25, accepted in 2012-06-18,  发布年份 2012

来源: Springer

【 摘 要 】

BackgroundIn 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.MethodsWe 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.ResultsThis 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%.ConclusionThis 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.

【 授权许可】

CC BY   
© Luque Fernandez et al; licensee BioMed Central Ltd. 2012