The urban infection susceptibility index and its application in cities of China

Infectious diseases pose a serious threat to human health and social safety. In order to better respond to large-scale outbreaks of infectious diseases in the context of climate change, it is essential to identify potential high-risk areas in cities. However, there is currently a lack of a standardized metric or indicator for quantifying the potential risk of urban infectious diseases. The main objective of this study is to construct an urban infection susceptibility index (UISI) to identify and quantify susceptibility risk, thereby providing insights for constraining and prevent future epidemics. The UISI considers both human activities (population density, closeness index, betweenness index, life service, functional synthesis indicator, hospital accessibility) and climate-related factors (temperature, particulate matter 2.5, wind speed, humidity), and is specifically designed to analyze potential high-risk areas of urban epidemics across cities worldwide. The index integrates a wide range of factors based on the criteria importance obtained through the intercriteria correlation method, producing fine-scale susceptibility maps at the urban grid level. We apply the UISI to the coronavirus disease 2019 risk assessment in Lanzhou and Shanghai, which has been well verified. This UISI is both easy and effective to calculate across various cities, providing a scientific basis for rapid policy-making and implementation to prevent the spread of infectious diseases. Furthermore, we predict the UISI trends across different shared socioeconomic pathways (SSP), specifically SSP5-8.5 and SSP2-4.5, which demonstrate an increasing trend from 2025 to 2100.