Estimating the time-varying reproduction number of COVID-19 with a state-space method
Fig 1
Schematic description of the Hawkes process Eq (1).
The occurrence rate λ(t) is increased according to past events occurred at times t = tk (k = 1, 2, …) with the transmission delays t − tk distributed with ϕ(t − tk). R is the reproduction number that represents the average number of events induced by a single event.