Increasing Probability of Outbreak of Dengue in Asian Metropolises Under Global Warming of 1·5°C- 4°C

Background: Climate factors drive the spread of dengue. Global warming affects the mosquito habitat and the transmission of dengue, especially in densely populated urban areas.<br><br>Methods: Transfer functions from climate to mosquito and from mosquito to disease are set up using the Generalized Additive Model (GAM) and Susceptible Infected Recovered Model (SIR), respectively, to project distribution patterns of mosquito density in Asia and changes of dengue incidence in Asian metropolises at global warming of 1·5°C, 2°C, 3°C and 4°C above the pre-industrial level, based on multi-model outputs from Coupled Model Inter-comparison Project Phase 6 (CMIP6). <br><br>Findings: With high temperature, high humidity, and dense population, urban areas in South and Southeast Asia have favorable conditions for dengue fever transmission. In a warming world, the area suitable for dengue transmission is expected to expand in Asia. It is projected that Arabian Peninsula, north of South Asia, and north of East Asia will be under an emergent risk for dengue transmission. In the reference period (1995-2014), about 180 (multi-model range 170~193) million people were exposed to dengue, accounting for a quarter of the total population in Asian metropolises. More population is projected to be exposed to dengue in future. Population exposure in Asian metropolises might increase to 261 (range: 181~300) million, 268 (range: 228~326) million, 287 (range: 241~361) million, and 287 (range: 241~367) million, respectively, at 1·5°C, 2°C, 3°C, and 4°C warming levels. Metropolises with population of more than 10 million have 51% higher morbidity of dengue than smaller cities. Taking all urban population as a whole, increase of dengue fever cases in Asian metropolises is projected to be 90% (range: 77%~127%), 107% (range: 80%~180%), 152% (range: 119%~314%), and 186% (range: 146%~325%), respectively, under different warming scenarios, relative to 260 thousand per year in the reference period. <br><br>Interpretation: Transmission of mosquitoes is determined mostly by temperature and precipitation conditions. Increasing temperature and precipitation in large parts of Asia in a global warming context expands the range of dengue fever. Although different cities show various climatic and socioeconomic characteristics, results consistently show that number of dengue cases may increase in Asian metropolises in future, which will bring huge challenges related to prevention and control of infectious diseases.<br><br>Funding Statement: National Key Research and Development Program of China (2017YFA0603804) and the Cooperation Project of Cooperation Group (GZ 1486) in the Chinese and German Center of the Research Promotion, NSFC/DFG.<br><br>Declaration of Interests: The authors declare no competing interests.