Cholera risk in Lusaka: A geospatial analysis to inform improved water and sanitation provision

Abstract

Urbanization combined with climate change are exacerbating water scarcity for an increasing number of the world’s emerging cities. Water and sanitation infrastructure (WSS), which in the first place was largely built to cater only to a small subsector of developing city populations, is increasingly coming under excessive strain. In the rapidly growing cities of the developing world, infrastructure expansion does not always keep pace with population demand, leading to waterborne diseases such as cholera (Vibrio cholerae) and typhoid (Salmonella serotype Typhi). Funding gaps make targeting efficient spending on infrastructure essential for reducing the burden of disease. This paper applies geospatial analysis in Lusaka, Zambia for the cholera outbreak of October 2017—May 2018, to identify different WSS investment scenarios and their relative impact on reducing the risk of cholera in the city. The analysis uses cholera case location data and geospatial covariates, including the location of networked and non-networked WSS infrastructure, groundwater vulnerability, and drainage, to generate a high-resolution map of cholera risk across the city. The analysis presents scenarios of standalone or combined investments across sewerage expansion and maintenance; on-site sanitation improvements; piped water network expansion and quality; and ensuring the safety of point-source water. It identifies the investment most strongly correlated with the largest reduction in cholera risk as the provision of flush-to-sewer infrastructure citywide. However, it also considers the trade-offs in terms of financial cost vs. health benefits and takes note of where the next highest health benefits could be achieved for a much lower cost. Finally, the analysis was conducted during the restructuring of an existing World Bank investment, the Lusaka Sanitation Program (LSP), and identifies the most efficient investment at the time as partial sanitation scale-up and investment in piped water in wards where cholera risk was the highest.