MERS-CoV spillover at the camel-human interface

Gytis Dudas; Luiz Max Carvalho; Andrew Rambaut; Trevor Bedford; Ali M. Somily; Mazin Barry; Sarah S. Al Subaie; Abdulaziz A. BinSaeed; Fahad A. Alzamil; Waleed Zaher; Theeb Al Qahtani; Khaldoon Al Jerian; Scott J.N. McNabb; Imad A. Al-Jahdali; Ahmed M. Alotaibi; Nahid A. Batarfi; Matthew Cotten; Simon J. Watson; Spela Binter; Paul Kellam

This empirically estimated effectived population can be compared to the expected effective population size in a simple epidemiological model. At endemic equilibrium, we expect 10 . CC-BY-NC 4.0 International license is made available under a The copyright holder for this preprint (which was not peer-reviewed) is the author/funder. It . https://doi.org/10.1101/173211 doi: bioRxiv preprint scaled effective population size N e τ to follow I / 2β, where β is the equilibrium rate of transmission and I is the equilibrium number of infecteds (Frost and Volz, 2010) . We assume that β is constant and is equal to the rate of recovery. Given a 20 day duration of infection in camels (Adney et al., 2014) , we arrive at β = 365/20 = 18.25 infections per year. Given extremely high seroprevalence estimates within camels in Saudi Arabia (Müller et al., 2014; Corman et al., 2014; Chu et al., 2014; Reusken et al., 2013 Reusken et al., , 2014 , we expect camels to usually be infected within their first year of life. Therefore we can estimate the rough number of camel infections per year as the number of calves produced each year. We find there are 830 000 camels in Saudi Arabia (Abdallah and Faye, 2013) and that female camels in Saudi Arabia have an average fecundity of 45% (Abdallah and Faye, 2013). Thus, we expect 830 000 × 0.50 × 0.45 = 186 750 new calves produced yearly and correspondingly 186 750 new infections every year, which spread over 20 day intervals gives an average prevalence of I = 10 233 infections. This results in an expected scaled effective population size N e τ = 280.4 years.