[Accessed 3 August 2013]
Risk Map of Cholera Infection for Vaccine Deployment: The Eastern Kolkata Case
Young Ae You, Mohammad Ali, Suman Kanungo, Binod Sah, Byomkesh Manna, Mahesh Puri, G. Balakrish Nair, Sujit Kumar Bhattacharya, Matteo Convertino, Jacqueline L. Deen, Anna Lena Lopez, Thomas F. Wierzba, John Clemens, Dipika Sur
Despite advancement of our knowledge, cholera remains a public health concern. During March-April 2010, a large cholera outbreak afflicted the eastern part of Kolkata, India. The quantification of importance of socio-environmental factors in the risk of cholera, and the calculation of the risk is fundamental for deploying vaccination strategies. Here we investigate socio-environmental characteristics between high and low risk areas as well as the potential impact of vaccination on the spatial occurrence of the disease.
Methods and Findings
The study area comprised three wards of Kolkata Municipal Corporation. A mass cholera vaccination campaign was conducted in mid-2006 as the part of a clinical trial. Cholera cases and data of the trial to identify high risk areas for cholera were analyzed. We used a generalized additive model (GAM) to detect risk areas, and to evaluate the importance of socio-environmental characteristics between high and low risk areas. During the one-year pre-vaccination and two-year post-vaccination periods, 95 and 183 cholera cases were detected in 111,882 and 121,827 study participants, respectively. The GAM model predicts that high risk areas in the west part of the study area where the outbreak largely occurred. High risk areas in both periods were characterized by poor people, use of unsafe water, and proximity to canals used as the main drainage for rain and waste water. Cholera vaccine uptake was significantly lower in the high risk areas compared to low risk areas.
The study shows that even a parsimonious model like GAM predicts high risk areas where cholera outbreaks largely occurred. This is useful for indicating where interventions would be effective in controlling the disease risk. Data showed that vaccination decreased the risk of infection. Overall, the GAM-based risk map is useful for policymakers, especially those from countries where cholera remains to be endemic with periodic outbreaks.
Citation: You YA, Ali M, Kanungo S, Sah B, Manna B, et al. (2013) Risk Map of Cholera Infection for Vaccine Deployment: The Eastern Kolkata Case. PLoS ONE 8(8): e71173. doi:10.1371/journal.pone.0071173
Editor: Matteo Convertino, University of Florida, United States of America
Received: April 11, 2013; Accepted: June 25, 2013; Published: August 2, 2013
Funding: This study is supported by the Bill & Melinda Gates Foundation through the Diseases of the Most Impoverished Program and the Cholera Vaccine Initiative. Additional funding is provided by the Swedish International Development Cooperation Agency and the Governments of South Korea, Sweden, and Kuwait. No funding bodies had any role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.