West Africa Ebola Outbreak 2013-2014: Disease, Treatments, and Global Impact

Jill E. Weatherhead, MD; Laila Woc-Colburn, MD


February 03, 2015

In This Article

A Look Back: Comparing Outbreaks

EVD first appeared in 1976 in two outbreaks in Nzara, Sudan, and Yambuku, Democratic Republic of Congo.[4] Previous outbreaks in Central Africa were limited in size and geographic spread, owing to the remote rural location of outbreaks.[5]

The size of the previous outbreaks and the case-fatality rates also varied but have remained significantly lower than in the current epidemic. Before the 2013-2014 epidemic, the largest outbreak occurred in Uganda in 2000 with the Sudan virus strain and had a case-fatality rate of 53%.[4] Case-fatality rates have ranged from 25% to 90% among all preceding outbreaks.[2,4]

Of interest, when the current epidemic is compared with previous outbreaks, the duration of illness, incubation periods, case-fatality rate, and average number of secondary cases that arise when one primary case is introduced into an uninfected population (ranging from 1.20 to 1.83 in the current outbreak) are similar.[5] Although the transmissibility of the virus and the clinical course of the infected virus are similar to previous outbreaks, the current epidemic is much larger in scale—larger than all previous outbreaks of Ebola virus combined.[1]

The expansion of this epidemic compared with previous outbreaks stems from the interconnectedness of people. In these regions, there has been heavy cross-border traffic and easier connections by road between rural towns and densely populated cities compared with previous outbreaks.[5] Travel to other continents has expanded in scope and speed, putting infected people in closer contact with the uninfected.[1,5] The interconnectedness of people has made control efforts challenging as well.[5] However, such areas as Nigeria and Senegal, which are now determined to be Ebola-free, have been able to implement adequate control measures despite introduction of EVD into large cities.[1,5]


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