Early dynamics of transmission and control of COVID-19: a mathematical modelling study

Adam J Kucharski; Timothy W Russell; Charlie Diamond; Yang Liu; John Edmunds; Sebastian Funk; Rosalind M Eggo

To examine the potential for new outbreaks to establish in locations outside of Wuhan, we used our estimates of the reproduction number to simulate new outbreaks with potential individual-level variation in transmission (i.e. 'superspreading events') (13, 19, 20) . Such variation increases the fragility of transmission chains, making it less likely that an outbreak will take off following a single introduction; if transmission is more homogeneous, with all infectious individuals generating a similar number of secondary cases, it is more likely than an outbreak will establish (19) . Based on the median reproduction number estimated during January before travel restrictions were introduced, we estimated that a single introduction of 2019-nCoV with SARS-like or MERS-like individual-level variation in transmission would have a 20-28% probability of causing a large outbreak ( Figure 3A ). Assuming SARS-like variation and Wuhan-like transmission, we estimated that once four or more infections have been introduced into a new location, there is an over 50% chance that an outbreak will occur ( Figure 3B ).