Fig. 2
From: Optimal timing and effectiveness of COVID-19 outbreak responses in China: a modelling study
State transition diagram for models of other Chinese cities (Chongqing, Beijing, and Shanghai). States include Susceptible (S), Exposed (E), Infected and asymptomatic (IA), Infected and symptomatic (IS), and Recovered (R). Subscript L denotes compartments for the local city population, while subscript W denotes individuals who have arrived from Wuhan. Compartments with subscripts Q1 through Q14 are used to represent a 14-day isolation period for travelers arriving from Wuhan. When travel history screening is active, individuals arriving from Wuhan enter the set of Q1 compartments. After progressing through the 14 quarantine states, individuals return to the corresponding non-quarantined compartments, except for those in the IS compartment who remain quarantined until their illness is resolved (either through recovery or death)