Background: In this study, we aimed to quantify the contribution of different transmission routes of the MiddleEast respiratory syndrome (MERS) and determine its transmissibility. Methods: Based on the natural history and transmission features of MERS in different countries, a susceptibleexposed-symptomatic-asymptomatic-recovered/death (SEIARD) model and a mult-route dynamic modelMMDM). The SEIARD model and MMDM were adopted to simulate MERS in South Korea and Saudi Arabiarespectively. Data on reported MERS cases in the two countries were obtained from the World Health Organization, Thereafter, the next generation matrix method was employed to derive the equation for the basicreproduction number (Ro), and the model fitting procedure was adopted to calculate the Ro values correspondingto these different countries. Results: In South Korea, Person-to-Person' transmission was identified as the main mode of MERS transmission inhealthcare settings, while in Saudi Arabia, in addition to Person-to-Person’transmission, Host-to-Host’andHost-to-Person’transmission also occurred under certain scenarios, with camels being the main host, Furtherthe fitting results showed that the SEIARD model and MMDM fitted the data well, The mean R, value was 8.59(95% confidence interval (CI: 0-28.02) for MERS in South Korea, and for MERS in Saudi Arabia, it was 1.15 and1.02 (95% CI: 0.86-1.44) for the ‘Person-to-Person’ and ‘Camel-to-Camel’ transmission routes, respectively. Conclusions: The SEIARD and MMDM model can be used to simulate the transmission ofMERS in different countriesAdditionally, in Saudi Arabia, the transmissibility of MERS was almost the same among hosts (camels) and humans
