The Novel Coronavirus, 2019-nCoV, Is Highly Contagious And More Infectious Than Initially Estimated

Fig. 3. Estimation of the basic reproductive number, R0, and the impact of control measures. (A) Histograms and the means (stars) of estimated R0 assuming individuals become infectious at symptom onset (blue) or 2 days before symptom onset (orange). The dotted line denotes R0=1. (B) The levels of minimum efforts (lines) of intervention strategies needed to control the virus spread. Strategies considered are quarantine of symptomatic individuals and individuals who had contacts with them (x-axis) and population-level efforts to reduce overall contact rates (y-axis). Different colored lines denote different assumptions of the fraction of asymptomatic individuals in the infected population. Solid and dashed lines correspond to R0=4.7 and 6.3 (i.e. the estimated means of R0), respectively. (C) The cumulative number of cases outside of Hubei province in late January 2020. The growth rate decreased to 0.14 per day since January 30. The dashed black line shows January 23 when Wuhan is locked down. Source

Abstract 

The novel coronavirus (2019-nCoV) is a recently emerged human pathogen that has spread widely since January 2020. Initially, the basic reproductive number, R0, was estimated to be 2.2 to 2.7. Here we provide a new estimate of this quantity. We collected extensive individual case reports and estimated key epidemiology parameters, including the incubation period. Integrating these estimates and high-resolution real-time human travel and infection data with mathematical models, we estimated that the number of infected individuals during early epidemic double every 2.4 days, and the R0 value is likely to be between 4.7 and 6.6. We further show that quarantine and contact tracing of symptomatic individuals alone may not be effective and early, strong control measures are needed to stop transmission of the virus. Source

............The 2019-nCoV epidemic is still rapidly growing and spread to more than 20 countries as of February 5, 2020. Here, we estimated the growth rate of the early outbreak in Wuhan to be 0.29 per day (a doubling time of 2.4 days), and the reproductive number, R0, to be between 4.7 to 6.6 (CI: 2.8 to 11.3). Among many factors, the Lunar New Year Travel rush in early and mid-January 2020 may or may not play a role in the high outbreak growth rate, although SARS epidemic also overlapped with the Lunar New Year Travel rush. How contiguous the 2019-nCoV is in other countries remains to be seen. If the value of R0 is as high in other countries, our results suggest that active and strong population-wide social distancing efforts, such as closing down transportation system, schools, discouraging travel, etc., might be needed to reduce the overall contacts to contain the spread of the virus. Source