A preprint by Julien Riou and Christian L. Althaus estimates the basic reproduction number (R0) of the 2019-nCoV virus, finding it to be around 2.2 (90% high density interval 1.4–3.8), indicating the potential for sustained human-to-human transmission. This is comparable to SARS-CoV and the 1918 pandemic influenza. The study uses stochastic simulations of early outbreak trajectories consistent with epidemiological findings. The results suggest that the virus has the potential for sustained human-to-human transmission, with a high probability of superspreading events. The study also highlights the importance of heightened screening, surveillance, and control efforts, particularly at airports and other travel hubs, to prevent further international spread of 2019-nCoV. The findings underscore the need for international collaboration and coordination to contain the spread of the virus. The study is the first to focus on the quantification of early human-to-human transmission of 2019-nCoV and provides a reliable summary of the current state of knowledge about its transmissibility. The analysis, while limited by the scarcity of data, has two important strengths: it is based on the simulation of a wide range of possibilities regarding epidemic parameters and allows for the full propagation of the many remaining uncertainties regarding 2019-nCoV and the situation in Wuhan. The study also emphasizes the importance of controlling superspreading events in hospital settings, as has been shown by the examples of MERS-CoV in South Korea and Saudi Arabia. The findings highlight the importance of heightened screening, surveillance, and control efforts to prevent further international spread of 2019-nCoV.A preprint by Julien Riou and Christian L. Althaus estimates the basic reproduction number (R0) of the 2019-nCoV virus, finding it to be around 2.2 (90% high density interval 1.4–3.8), indicating the potential for sustained human-to-human transmission. This is comparable to SARS-CoV and the 1918 pandemic influenza. The study uses stochastic simulations of early outbreak trajectories consistent with epidemiological findings. The results suggest that the virus has the potential for sustained human-to-human transmission, with a high probability of superspreading events. The study also highlights the importance of heightened screening, surveillance, and control efforts, particularly at airports and other travel hubs, to prevent further international spread of 2019-nCoV. The findings underscore the need for international collaboration and coordination to contain the spread of the virus. The study is the first to focus on the quantification of early human-to-human transmission of 2019-nCoV and provides a reliable summary of the current state of knowledge about its transmissibility. The analysis, while limited by the scarcity of data, has two important strengths: it is based on the simulation of a wide range of possibilities regarding epidemic parameters and allows for the full propagation of the many remaining uncertainties regarding 2019-nCoV and the situation in Wuhan. The study also emphasizes the importance of controlling superspreading events in hospital settings, as has been shown by the examples of MERS-CoV in South Korea and Saudi Arabia. The findings highlight the importance of heightened screening, surveillance, and control efforts to prevent further international spread of 2019-nCoV.