>We estimate the basic reproduction number of the infection (R_0) to be 3.8 (95% confidence interval, 3.6-4.0), indicating that 72-75% of transmissions must be prevented by control measures for infections to stop increasing. We estimate that only 5.1% (95%CI, 4.8-5.5) of infections in Wuhan are identified, and by 21 January a total of 11,341 people (prediction interval, 9,217-14,245) had been infected in Wuhan since the start of the year. Should the epidemic continue unabated in Wuhan, we predict the epidemic in Wuhan will be substantially larger by 4 February (191,529 infections; prediction interval, 132,751-273,649), infection will be established in other Chinese cities, and importations to other countries will be more frequent.
