[TomGuy]

plane ... from Johannesburg

So, how many people did this 'infested' one come in contact with while still in Johannesburg? And how many of those got on other planes or went into the city?

IIRC, the infectious period could from 2 to 21 days. That could create a wide spread of contamination. But the CDC tells us there is nothing to worry about.

[iontheball]

plane ... from Johannesburg
_______________________________________________
Yes, and where had he been before Johannesburg?