Contributors: Stacy Soh1, Soon Hoe Ho1, Annabel Seah1, Janet Ong1, Daniel R Richards2, Leon Yan-Feng Gaw3, Borame Sue Dickens4, Ken Wei Tan4, Joel Ruihan Koo4, Alex R Cook4, Jue Tao Lim1,4
1Environmental Health Institute, National Environment Agency, Singapore
2Manaaki Whenua - Landcare Research, New Zealand
3Department of Architecture, School of Design and Environment, National University of Singapore, Singapore
4Saw Swee Hock School of Public Health, National University of Singapore and National University Health System, Singapore
Dengue is a major vector-borne arboviral disease affecting much of the world. Dengue outbreaks typically impose a strain on healthcare systems by increasing demand for healthcare resources. However, little work has been done to characterise the spatial extent of these extreme dengue outbreaks and their associated drivers. In this paper, we examined extreme dengue outbreak risk over locales in Singapore from 2007 to 2020, accounting for spatial heterogeneity in these events using max-stable processes. The return levels associated with the different sites, which were the weekly dengue case counts expected to be exceeded once every specific number of years, were then determined. Return levels were consistently higher in the eastern parts of Singapore, with the maximum weekly dengue cases expected to exceed 51 cases at least once in 30 years in most spatial units (approximately 0.072 km each). The age of public apartments and impervious surfaces had the largest impact on outbreak risk, driving up to a 3.8% and 3.3% increase respectively given a 3 year and 10% increase in the spatial unit. Vegetation with human management, freshwater surfaces and population size were also associated with higher outbreak risk. Our study extends standard tools used in Extreme Value Theory to conduct inference on the spatial behaviour of extreme dengue outbreak risk and its drivers. Public health agencies should prioritise their vector control efforts in older residential estates and localities where there are large contiguous masses of built-up environment, where extreme dengue outbreak risk is high. The developed methods and findings serve to inform public health officials on the likely scale of outbreaks in the longer term and may be used to inform long-term spatially resolved resource planning and risk mitigation