Introduction: The emergence of the novel MERS-CoV virus in the Middle East (ME) in 2012, followed by its international spread, has raised concerns for global public health. Initial characterization of the epidemic and its transmission potential was difficult due to uncertainties regarding the reservoir and modes of transmission. Furthermore, epidemiological data were limited, reducing the power of statistical analyses and modeling. Method: We present here an integrative approach based on the joint analysis of clustered cases in the MO and imported cases in the European community. This approach allows for the most comprehensive analysis at this stage, as it incorporates transmission from an animal reservoir, underreporting of cases, and international mobility via air travel. Results: The estimate based on data collected through August 31, 2013, shows that the epidemic remains subcritical (R = 0.50, 95% CI 0.30–0.77) with the introduction of approximately 2 (95% CI 0.8–6) new cases via animal-to-human transmission. Infections in the region are currently largely dominated by this zoonotic source, with potentially significant underreporting (ratio of estimated to observed introductions equal to 2.41, 95% CI 1.03–7.32). Conclusion: The approach developed demonstrates its value in guiding public health decision-making by enabling the quantification of the relative role of transmission routes, the likely size of the outbreak, and its potential for international spread. The combination of different sources (case clusters, air travel) has enhanced the explanatory power of the available information, making it a model applicable to other emerging epidemics. (R.A.)