Preliminary estimation of the basic reproduction number of novel coronavirus (2019-nCoV) in China, from 2019 to 2020: A data-driven analysis in the early phase of the outbreak

Backgrounds There has been a novel coronavirus (2019-nCoV) pneumonia outbreak in China since December 2019, and which spreads internationally. This is the first study to quantify the basic reproduction number, R₀, of 2019-nCoV in the early phase of the outbreak.

Methods Accounting for the impact of the variations in disease reporting rate, we modelled the epidemic curve of 2019-nCoV cases time series, in mainland China from January 10 to January 21, 2020, through the exponential growth. With the estimated intrinsic growth rate (γ), we estimated R₀ by using the serial intervals (SI) of two other well-known coronavirus diseases, MERS and SARS, as approximations for the true unknown SI.

Findings The early outbreak data largely follows the exponential growth. We estimated that the mean R₀ ranges from 3.30 (95%CI: 2.73-3.96) to 5.47 (95%CI: 4.16-7.10) associated with 0-fold to 2-fold increase in the reporting rate. With rising report rate, the mean R₀ is likely to be below 5 but above 3.

Conclusion The mean estimate of R₀ for the 2019-nCoV ranges from 3.30 (95%CI: 2.73-3.96) to 5.47 (95%CI: 4.16-7.10), and significantly larger than 1. Our findings indicate the potential of 2019-nCoV to cause outbreaks.