[thackney]

When you follow the link back to the WHO report, you find it does not match the claims in the article.

http://www.who.int/mediacentre/news/ebola/14-october-2014/en/

The period of 42 days, with active case-finding in place, is twice the maximum incubation period for Ebola virus disease and is considered by WHO as sufficient to generate confidence in a declaration that an Ebola outbreak has ended.

[amihow]

Thank you. The reason for 42 ‘days is that on day 21with no REPORTED cases out in boonies someone may have it and start wave of new infections? What should we do?

[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.

[justa-hairyape]

With 95 % certainty. Good enough for government work I guess.