Although scientists report that 21 days is an adequate duration for quarantining patients suspected of Ebola exposure, a study published in PLOS Current Outbreaks suggests more research is needed to determine optimal  duration time.

“The precise origin of this assessment is unclear, however it is possibly based on the study of the either the 1976 Zaire outbreak or 2000 Uganda outbreak both of which reported (without detailed analysis) a maximum observed incubation time of 21 days,” noted Charles N. Haas, MD, of Drexel University in Philadelphia.

To examine quarantine durations, Haas studied prior estimates for incubation time in patients with Ebola and data on the first nine months of the current Ebola outbreak, which provided estimates of the distribution of incubation times.

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A 21-day period for quarantine may result in the release of patients with a 0.2% to 12% risk of release prior to full opportunity for the incubation to proceed, found Haas.

“Outbreaks such as the current West Africa EBOV are presenting an opportunity for careful collection of data sufficient to revise and update (perhaps in an adaptive fashion) such recommendations,” concluded Haas.

“It may be that incubation time itself is a function of intensity and nature of contact, which may also need to be considered.”


  1. Haas CN. PLOS Current Outbreaks. 2014; doi: 10.1371/currents.outbreaks.2ab4b76ba7263ff0f084766e43abbd89