The Impact of COVID–19 Lockdown on Dengue Transmission in Sri Lanka; A Natural Experiment for Understanding the Influence of Human Mobility

Abstract

Background: Dengue is one of the major public health problems in Sri Lanka. It´s outbreak pattern depends on a multitude of drivers, including human mobility. Here we evaluate the impact of COVID–19 related mobility restriction (lockdown) on the risk of dengue in Sri Lanka.Methods: Two-stage hierarchical models were fitted using an interrupted timeseries design based on the notified dengue cases, January 2015 to July 2020. In the first stage model, the district level impact was estimated using quasi-Poisson regression models while accounting for temporal trends. Estimates were pooled at zonal and national levels in the second stage model using meta-analysis. The influence of the extended period of school closure on dengue in children in the western province was compared to adults.Results: Statistically significant and homogeneous reduction of dengue risk was observed at all levels during lockdown. Overall an 88% reduction in risk (RR 0·12; 95% CI from 0·08 to 0·17) was observed at the national level. The highest impact was observed among children aged less than 19 years showing 92% reduction (RR 0·09; 95% CI from 0·05 to 0·15). We observed higher impact on the dry zone having 91% reduction (RR 0·09; 95% CI from 0·05 to 0·15) compared to wet zone showing 73% reduction (RR 0·17; 95% CI from 0·09 to 0·30). Interpretation: This study offers a broad understanding on the change in risk of dengue during the COVID–19 pandemic and associated mobility restrictions in Sri Lanka. The analysis using the mobility restrictions as a natural experiment suggest mobility patterns are a very important driver of dengue.Funding: None.Conflict of Interest: We declare no competing interests.