Once successfully initiated, an epidemic may initially hover around a handful of cases before reaching a sufficient number of cases for its growth to become essentially predictable. As mentioned, 20 concurrent cases is our criterion for an epidemic to have gathered momentum. We determine the distribution of D 2 , the time to this occurrence, from 10,000 stochastic simulations and approximate this empirical distribution by a shifted gamma distribution. Our criterion of 20 concurrent cases is conservatively high, as results from the theory of branching processes shows that the probability of a minor epidemic (and hence no take-off) starting from 20 concurrent cases is about 3610 28 when R = 1.5, and even smaller for higher values of R. Finally, the distribution of the total delay (D = D 1 +D 2 ) from the pandemic being identified in the source region until 20 cases in the at-risk country was calculated by the convolution of the distributions of D 1 and D 2 .