Real-time monitoring the transmission potential of COVID-19 in Singapore, February 2020

Abstract The ongoing COVID-19 epidemic that spread widely in China since December 2019 is now generating local transmission in multiple countries including Singapore as of February 27, 2020. This highlights the need to monitor in real time the transmission potential of COVID-19. In Singapore, four major COVID-19 case clusters have emerged thus far. Here we estimate the effective reproduction number, Rt, of COVID-19 in Singapore from the publicly available daily case series of imported and autochthonous cases by date of symptoms onset, after adjusting the local cases for reporting delays. We also derive the reproduction number from the distribution of cluster sizes using a branching process analysis. The effective reproduction number peaked with a mean value ~1.1 around February 2nd, 2020 and declined thereafter. As of February 27th, 2020, our most recent estimate of Rt is at 0.5 (95% CI: 0.2,0.7) while an estimate of the overall R based on cluster size distribution is at 0.7 (95% CI: 0.5, 0.9). The trajectory of the reproduction number in Singapore underscore the significant effects of containment efforts in Singapore while at the same time suggest the need to sustain social distancing and active case finding efforts to stomp out all active chains of transmission.