“In any case, getting exposed to Ebola, obtaining a visa to the US, and procuring tickets would be a lot to accomplish in three or four days.”
So, he most likely applied for and got the visa well in advance, then purchased the ticket on the 2nd, with the ticket being for a specific flight (day and time), then was exposed to Ebola a day or two before his flight was scheduled, and then boarded as per.......?