Osong Public Health Res Perspect.  2011 Jun;2(1):3-7. 10.1016/j.phrp.2011.04.001.

Incubation Period of Ebola Hemorrhagic Virus Subtype Zaire

• Eichner M
• Dowell SF
• Firese N

• KMID: 2517957
• DOI: http://doi.org/10.1016/j.phrp.2011.04.001

Abstract

Objectives
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.
Conclusion
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.

Keyword

disease outbreaks/prevention & control; Ebola/epidemiology; Ebola hemorrhagic fever; Ebola/prevention & control; statistical models