title: Incubation period of ebola hemorrhagic virus subtype zaire.
abstract: OBJECTIVE
  Ebola hemorrhagic fever has killed over 1300 people, mostly in equatorial Africa. There is still uncertainty about the natural reservoir of the virus and about some of the factors involved in disease transmission. Until now, a maximum incubation period of 21 days has been assumed.
  
  
  METHODS
  We analyzed data collected during the Ebola outbreak (subtype Zaire) in Kikwit, Democratic Republic of the Congo, in 1995 using maximum likelihood inference and assuming a log-normally distributed incubation period.
  
  
  RESULTS
  The mean incubation period was estimated to be 12.7 days (standard deviation 4.31 days), indicating that about 4.1% of patients may have incubation periods longer than 21 days.
  
  
  CONCLUSIONS
  If the risk of new cases is to be reduced to 1% then 25 days should be used when investigating the source of an outbreak, when determining the duration of surveillance for contacts, and when declaring the end of an outbreak.
authors.affiliation: Department of Medical Biometry, University of Tübingen, Tübingen, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Eichner
authors.forename: Scott F
authors.initials: SF
authors.lastname: Dowell
authors.forename: Nina
authors.initials: N
authors.lastname: Firese
keywords: Ebola hemorrhagic fever; Ebola/epidemiology; Ebola/prevention & control; disease outbreaks/prevention & control; statistical models