You should catch up on your reading. Illegal immigrants have been nabbed in Albania and Pisa Italy, and some are showing symptoms. It can get as far as people can get in an incubation period that ranges from 2 to 21 days, depending on initial viral load.
In short, anywhere in the world, via air travel.
While most people in the affected region are too poor to even consider air travel, there are numerous natives and a host of US expatriates there working in the oil industry. The potential to spread globally exists. These will be people who do not yet know they are infected, unlike Sawyer, who likely knew and was already symptomatic when he was on the plane.
BTW, President Goodluck Jonathan of Nigeria just FIRED 16,000 striking doctors. Talk about poor timing! Plus the amount of corrupt stealing in that country by the government would easily pay for their increased wage demands.