Incubation Period of Ebola Hemorrhagic Virus Subtype Zaire

Abstract

ObjectivesEbola 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.MethodsWe 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.ResultsThe 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.ConclusionIf 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.

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“…We estimated R 0 from the data by extending the modeling approach that provided the first estimates of R 0 for the 2014 EVD epidemics in Guinea, Sierra Leone and Liberia (Althaus, 2014). Our estimates of the average periods of incubation and infectiousness, which were based on historical data from the 1976 outbreak in Zaire (Breman et al, 1978) and the first cases of the 2013/2014 outbreak in Guinea (Baize et al, 2014), are in good agreement with other estimates (Eichner et al, 2011;Chowell and Nishiura, 2014). In particular, the There are two main limitations related to the model structure.…”

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