Epidemic doubling time of the 2019 novel coronavirus outbreak by province in mainland China

We analyzed the epidemic doubling time of the 2019-nCoV outbreak by province in mainland China. Mean doubling time ranged from 1.0 to 3.3 days, being 2.4 days for Hubei (January 20-February 2, 2020). Trajectory of increasing doubling time by province indicated social distancing measures slowed the epidemic with some success.