Figure 1 Schematic illustrations of the model. (a) Hospital ward model showing the possible movements between wards in the health care facility. (b) Hospital ward model movement of people between wards within the health care facility. The parameters α i , j are the transition rates from unit i to unit j . The functions F and F ′ are the forces of infection imposed on susceptible patients and health care workers (HCWs), respectively. The mobile health care workers follow the same transitions between the disease compartments as other health care workers. The rate of isolation α i , 6 = : α 6 is assumed to be the same for any unit i . Finally, σ is the rate at which exposed people become symptomatic.

Figure 2 The strength of the outbreak. (a) The basic reproduction number R 0 at different times during the King Abdulaziz Medical City (KAMC) outbreak. (b) Evolution of proportion of infected patients, HCW, and HCWm for transmission rates at the levels of the last 10 days of the outbreak. The infection disease epidemic plan phase II (infectious disease epidemic plan (IDEP) II activated August 2–8) is on the time period days 43–49 on the time scale and phase III (IDEP III activated August 16–22) is on the time period days 57–63 on the time scale.

Figure 3 Sensitivity to the different parameters and measures. (a) Size of epidemics of patients, HCWs, and mobile HCWs’ sensitivity to the most influential parameters. The parameters from left to right: natural removal rate from environment ( δ ), transition from the emergency department (ED) to intensive care unit (ICU) ( α 2 , 4 ), rate of isolation ( α 6 ), transition from the ED to the hospital wards ( α 2 , 5 ), rate of becoming symptomatic ( σ ), relative reduction in transmission rates for exposed and asymptomatic ( c ), transmission rate of HCWs in the ED up to 45 days ( β 2 , H , 1 ), the parameter ϵ representing relative reduction in transmission from HCWs to patients due to, may be, infection control measures like using masks and gloves, transmission rate of patients in the ED after 26 days ( β 2 , 2 ), environmental transmission rate in the ED ( β ′ 2 ), transmission rate of patients in the ED up to 26 days ( β 2 , 1 ), and transmission rate of mobile HCWs after 13 days ( β m , 2 ). The size of the epidemic of patients and HCWs are still sensitive to β m , 2 but to a lesser degree; that is, an increase of 1% in S I P , and S I H requires about 3.6% and 4.4% increase in β m , 2 , respectively. (b) Evolution of proportion of infected patients, HCW, and mobile health care workers (HCWm) for the default of three times cleaning versus the scenario of one extra-cleaning.

Figure 4 The effect of the rate of isolation on the outbreak. An exponential-like decline in the size of the epidemic if the rate of isolation of suspected cases is within a range of 50% around the estimated value of 0.94 for (a) patients and (b) both types of HCWs. Local (c) and global (d) sensitivity of the values of R 0 over time to the rate of isolation ( α 6 ). In (d) partial rank correlation coefficient (PRCC) of the rate of isolation and R 0 over time shows a negative significant correlation (p-value = 0). That association weakened over time but stayed significant.