Monte Carlo Maximum Likelihood (MCML) method used to estimate the transmission potential of the A/H1N1 pandemic. (A) Schematic representation of the invasion dynamics of an emerging infectious disease from the seed subpopulation (red patch) to the neighboring subpopulations connected by means of mobility. The blue color code refers to the arrival time of the first infectious individual. Links of different width represent mobility connections characterized by different mobility flows. (B) Flow chart representing the steps that compose the Monte Carlo Maximum Likelihood (MCML) method. First, for each point in the parameter space, we ran 2,000 stochastic realizations, all with the same initial conditions. Second, for each run, we recorded the arrival times in the countries under study. Third, we compared the probability distribution built on the simulated arrival times with the empirically observed arrival times for each country. Finally, we evaluated the likelihood function to find its maximum value, corresponding to the set of parameters that best fits the data.