Modelling the spread of Middle East respiratory syndrome coronavirus (MERS-CoV) in Saudi Arabia

1 Middle East Respiratory Syndrome Coronavirus (MERS-CoV) has been persistent in 2 the Middle East region since 2012. Abundant scientific evidence showed that dromedary 3 camels are the primary host of the virus. Majority of human cases (i.e. 75% or 88%) are 4 due to human-to-human transmission, while the others are due to camel-to-human transmis5 sion. Mathematical modelling of MERS-CoV camel-to-camel transmission was lacking. Us6 ing the plug-and-play likelihood-based inference framework, we fitted a susceptible-exposed7 infectious-recovered-susceptible model of camels to the reported human cases with a constant 8 proportion of human cases from camels (i.e. either 25% or 12%). We considered two scenarios: 9 (i) the transmission rate among camels is time-varying with a constant spill-over rate from 10 camels to human, or (ii) the spill-over rate is time-varying with a constant transmission rate 11 among camels. Our estimated loss-of-immunity rate and prevalence of MERS-CoV infections 12 among camels largely matched previous serological or virological studies, shedding light on 13 this issue. We recommended including dromedary camels in animal surveillance and control of 14 MERS-CoV in Saudi Arabia which could help reduce their sporadic introductions to humans. 15