Figure 2

Schematic links of disease transmission and diagram of all possible transitions between the states of a SEIR model for the 3 populations: patients (1), nurses (2) and medical doctors (3). Each square corresponds to a specific state: susceptible (S), exposed (E) i.e. infected but not yet contagious, (I) infectious i.e. contagious and Removed (R) i.e. immune. Solid arrows indicate transition between the states and dotted arrows the influence of contagious individuals on the rate of transmission. The subscripts "1", "2", and "3" denote the patient, nurse and medical doctor populations, respectively. The infection rate for population \(i\) is denoted by \({\lambda }_{i}\), the number of new patients entering into K2 unit (or leaving K2 unit) per day by \({z}_{1}\), the probability for patients of being in a contagious state on admission at time \(t\) by \(\phi\), the average duration of latent period in population \(i\) by \({\sigma }_{i}^{-1}\), and the average infectious period in population \(i\) by \({\gamma }_{i}^{-1}\). Patient population is stable and patients leaving K2 unit each day had same chance to be in any state.