[Gennie]

From the link:

Recent studies conducted in West Africa have demonstrated that 95% of confirmed cases have an incubation period in the range of 1 to 21 days; 98% have an incubation period that falls within the 1 to 42 day interval. WHO is therefore confident that detection of no new cases, with active surveillance in place, throughout this 42-day period means that an Ebola outbreak is indeed over.

While 95% are confirmed by 21 days, there are 3% that seem to fall ill after this 21 day period.

[thackney]

That report then conflicts with its own writing in the paragraph before.

is twice the maximum incubation period