UNDERSTANDING THE CONNECTION BETWEEN THE HYDRO-CLIMATIC EXTREMES AND DIARRHEAL DISEASES OVER BENGAL DELTA: THE VULNERABILITY ASSESSMENT OF PAST, PRESENT AND FUTURE
Date of Award
Doctor of Philosophy in Civil and Environmental Engineering
Civil and Environmental Engineering
Ali S. Akanda
Living in the age of space exploration and nanotechnology, the significant portion of human population still have threatened by diarrheal diseases throughout the globe. Being a major contributor of the global mortality, the diarrheal diseases account for an estimated 3.1% of the total burden of disease in terms of Disability-Adjusted Life Year (DALY) where cholera and rotavirus diarrhea comprise more than two-thirds of the diarrheal morbidity in developing countries of South Asia.
Alongside with many more challenges like climate change or civil war, the capability to resolve the diarrheal disease burden in developing countries remains questionable. As the primary reasons for the disease transmission in epidemic scale are due to the exposure of contaminating pathogens via unsafe drinking water sources, lack of sanitation, deficient hygiene, insufficient drainage infrastructures and poor access to health care, ensuring clean water sources and improved sanitation may seem to untangle the problem. However, it will take a longer time to achieve such improvement by the developing countries as many of them are already missed the Millennium Development Goals (WHO/UNICEF 2015). Moreover, ongoing global climatic change also leads the disease vulnerability in much degrading state (Woodward et al. 2014). In this context, the Bengal delta of South Asia, exhibits the highest population density of globe and is one of the most vulnerable region of the world in terms of both climate change and diarrheal diseases (Bowen and Friel 2012). Therefore, the challenges to tackle the vulnerability of diarrheal disease under ongoing global warming is paramount in this region.
Previous studies found that the diarrhoeal diseases like cholera and rotavirus are significantly influenced by environmental factors in the developing counties of Asia and Sub Saharan Africa. The outbreaks of the diseases can occur in the wake of climatic extremes like heavy rainfall, flooding, cyclone, drought, extreme temperature and El-Nino (Bradley et al. 1996; Corwin et al. 1996; Patz et al. 2000; Vanasco et al. 2001; Chhotray et al. 2002; Kalashnikov et al. 2002; Qadri et al. 2005; Yang et al. 2005; Harmeling 2012). However, most studies have explored the influence on disease transmission for particular climatic extremes or related natural disasters, but the integration of multiple variables along with disease cases is infrequently done. Moreover, a deterministic quantification of the diseases epidemic based on the hydro-climatic factors is absent in existing literatures.
In terms of diarrheal disease epidemic as well as climate vulnerability, the Bengal delta is frequently considered as one of the high-risk region of the globe (IPCC, 2014). The policy makers of the region not only need to tackle the burden of diarrheal disease but also need to understand the future impact of these diseases under ongoing climate change. However, not only the future assessment of the disease is challenging but also, the meaningfully quantification of climatic extremes under future climate change scenarios require robust assessment due to the absence of such kind of studies.
Therefore, the objective is this dissertation is to develop the deterministic models that can project the future risk of diarrheal diseases, primarily rotavirus and cholera, driven by hydro-climatic extremes over the climate vulnerable region of Bengal delta. In order to achieve this objective, I developed a bias-correction method for the high-resolution regional climate models, generated an observed data set over the Bengal delta, formulated a deterministic epidemic model for rotavirus that accounts intra-annual variability, proposed a spatial risk model of rotavirus and cholera and projected the future of the diarrheal disease for 21st century. The work has been described in the following three manuscripts, as per the Graduate School Manual guidelines:
Chapter 1. MANUSCRIPT І (published in Climate Dynamics, 2017)
The objective of this work was to explore the climate and its extremes over a monsoon dominated country like Bangladesh by following the latest RCP (Representative Concentration Pathways) emission scenarios, considering fine scale regional physics, incorporating the uncertainties range, and also by conducting advance bias correction methods to accomplish most reliable future projections. In this relation, the article aimed to investigate (1) the future probabilistic climate of Bengal delta, using five regional climate model projections driven by GCM results, (2) to develop a new spatial gridded observed data that represents historical climate extremes set and (3) to implement the latest QM (Quantile Mapping) bias correction methods over multi-model RCM outputs.
Chapter 2. MANUSCRIPT ІI (published in Geo Health, 2018).
In this manuscript, we investigated the role of climatic extremes on one of the prevalent diarrheal disease, rotavirus. The study aimed (1) to determine the effect of climatic extremes on the rotavirus epidemic over Bangladesh, both in spatially and temporal scale (2) to evaluate the rotavirus patterns over the cities of South Asia to understand the relation of the virus to regional hydro climatic processes and (3) to implemented a deterministic multivariate modeling for risk assessment and integrating near real-time satellite products (with GPM for rainfall and MODIS for temperature).
Chapter 3. MANUSCRIPT ІII (prepared for International Journal of Biometeorology).
The objective of this manuscript was to project the future the diarrheal disease risk based on the epidemic models driven by the bias-corrected regional climate models. To implement the long-term development medical initiatives under ongoing climate change, the policy makers requires comprehensive and meaningfully estimate of the future vulnerability of the diseases. Thus, the manuscript aimed (1) to develop some spatial multivariate models of the rotavirus and cholera epidemic over Bengal delta, (2) to assess the effect of relative humidity on rotavirus cycle, and (3) to project the probable future risk during the rising phase for both the diseases in the early, mid and late 21st Century.
In conclusion, the diarrheal diseases are a recurrent burden in the developing world. Though there are many factors such as population dynamic, poor water sanitation and hygiene can be responsible for diarrhreal outbreak in the region, the climate drivers still can plays a significant role in the diseases epidemic thus essential to pre-epidemic management. As this study proposed a risk based methodology rather than prevalence or incidence based method, the method can overlook the influence of the population infectivity the disease and can be utilize to detect the influence of climatic change. This will allow the relevant stakeholders to improve the decision-making process. The novel approach and result of this dissertation can be utilized as a guideline for long-term diseases preparedness or vaccination strategy for Bangladesh. High-resolution regional model results will also provide valuable insight to the disease burden estimation which can be implemented in sub-district level with appropriate stakeholder. The findings of this study will be shared with ICDDRB (International Centre for Diarrhoeal Disease Research, Bangladesh) and Bill & Melinda Gates Foundation for further improvement of the vaccination and surveillance strategy over the region.
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Hasan, Mohammad Alfi, "UNDERSTANDING THE CONNECTION BETWEEN THE HYDRO-CLIMATIC EXTREMES AND DIARRHEAL DISEASES OVER BENGAL DELTA: THE VULNERABILITY ASSESSMENT OF PAST, PRESENT AND FUTURE" (2018). Open Access Dissertations. Paper 772.