21 days has been regarded as the appropriate quarantine period for holding individuals potentially exposed to Ebola Virus (EV) to reduce risk of contagion. There does not appear to be a systematic discussion of the basis for this period.
Links:
[1] http://admin.indiaenvironmentportal.org.in/feature-article/quarantine-period-ebola-virus
[2] http://admin.indiaenvironmentportal.org.in/category/author/charles-n-haas
[3] http://admin.indiaenvironmentportal.org.in/category/journal/plos-current-outbreaks
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/ebola-virus-disease-ebola-hemorrhagic-fever
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/research
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/infectious-diseases