Models. Demographic and social dynamics data for each region [77] were extracted from the U.S. Census [78] and the National Household Travel Survey [79] . Daily (hourly) schedules [77] were adopted from [53] . Each infected person was assigned a daily travel probability of 0.24% [79] , of which 7% was by air and 93% by land. The probabilities of travel among the four regions were calculated using traffic volume data [80] [81] [82] [83] , see Table 1 . Infection detection probabilities for border control for symptomatic cases were assumed to be 95% and 90%, for air and land, respectively [84] .