Fig 1. SEIR model.
Graphical scheme representing the interactions among different stages of infection in SEIR Model. In this model, Sit, Eit, , and Nit denote the susceptible, exposed, detected infected, undetected infected and total population in city i and time t. and are the rate of transmission for undetected infected individuals and detected infected individuals, respectively. αt is the testing rate in time t.Zt denotes latency period through which patients switch from exposed stage to infection stage. Ait is within-city population flow in city i in time t. Spatial spread of the disease is governed by the daily number of people travelling from city j to city i in time t(Mijt).