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A novel coronavirus (SARS-CoV-2) emerged as a global threat in December 2019. As the epidemic progresses, disease modellers continue to focus on estimating the basic reproductive number Formula: see text-the average number of secondary cases caused by a primary case in an otherwise susceptible population. The modelling approaches and resulting estimates of Formula: see text during the beginning of the outbreak vary widely, despite relying on similar data sources. Here, we present a statistical framework for comparing and combining different estimates of Formula: see text across a wide range of models by decomposing the basic reproductive number into three key quantities: the exponential growth rate, the mean generation interval and the generation-interval dispersion. We apply our framework to early estimates of Formula: see text for the SARS-CoV-2 outbreak, showing that many Formula: see text estimates are overly confident. Our results emphasize the importance of propagating uncertainties in all components of Formula: see text, including the shape of the generation-interval distribution, in efforts to estimate Formula: see text at the outset of an epidemic.
Park et al. (Wed,) studied this question.