The Novel Coronavirus, 2019-nCoV, is Highly Contagious and More Infectious Than Initially Estimated

Steven Sanche; Yen Ting Lin; Chonggang Xu; Ethan Romero-Severson; Nick Hengartner; Ruian Ke

Fortunately, we see evidence that control efforts have a measurable effect on the rate of spread. Since January 23, Wuhan and other cities in Hubei province implemented vigorous control measures, such as closing down transportation and mass gatherings in the city; whereas, other provinces also escalated the public health alert level and implemented strong control measures. We noted that the growth rate of the daily number of new cases in provinces outside of Hubei slowed down gradually since late January (Fig. 3B) . Due to the closure of Wuhan (and other cities in Hubei), the number of cases reported in other provinces during this period shall start to track local infection dynamics rather than imports from Wuhan. We estimated that the exponential growth rate is decreased to 0.14 per day (CI: 0.12 to 0.15 per day) since January 30. Based on this growth rate and an R0 between 4.7 to 6.6 before the control measures, a calculation following the formula in Ref. (14) suggested that a growth rate decreasing from 0.29 per day to 0.14 per day translates to a 50%-59% decrease in R0 to between 2.3 to 3.0. This is in agreement with previous estimates of the impact of effective social distancing during 1918 influenza pandemic (18) . Thus, the reduction in growth rate may reflect the impact of vigorous control measures implemented and individual behavior changes in China during the course of the outbreak.