Results : Our posterior estimates of basic reproduction number ( R ) in Wuhan City , China , in 2019 - 2020 reached values at 3 . 49 ( 95 % CrI 3 . 39 - 3 . 62 ) with a mean serial interval of 6 . 0 days , and the enhanced public health intervention after January 23 in 2020 was associated with a significantly reduced R at 0 . 84