Evaluation of risk of cholera after a natural disaster: Lessons learned from the 2015 Nepal earthquake

Uncertainty about the timing and the magnitude of natural disasters (such as floods, droughts, earthquakes) affects water resources planning and management in terms of the supply of safe drinking water and access to sanitation infrastructure. This in turn has a profound effect on human health. Drinking contaminated water often results in the outbreak of diarrheal infections (such as cholera, Shigella, and so on). Infectious pathogens (such as Vibrio cholerae) can survive in aquatic environments under appropriate hydroclimatic conditions. Therefore, the challenge is to estimate the risk of an outbreak of disease after a natural disaster occurs. Using cholera as a signature diarrheal disease and employing the weighted raster overlay method, a framework is presented for assessing the role of water resources, particularly water, sanitation and hygiene (WASH), in determining the likelihood of an outbreak of a disease in the human population. Results indicate that there were favorable hydroclimatic conditions for the survival of pathogenic cholera bacteria in natural water systems in the aftermath of the earthquake in Nepal in 2015. However, few cholera patients were reported in the country, indicating that the prevailing resilient WASH infrastructure played a pivotal role in deterring a disease outbreak.