Outbreaks of Ebola virus disease in Africa: the beginnings of a tragic saga
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REVIEW
Open Access
Outbreaks of Ebola virus disease in Africa: the beginnings of a tragic saga Jean-Philippe Chippaux1,2
Abstract The tremendous outbreak of Ebola virus disease occurring in West Africa since the end of 2013 surprises by its remoteness from previous epidemics and dramatic extent. This review aims to describe the 27 manifestations of Ebola virus that arose after its discovery in 1976. It provides an update on research on the ecology of Ebola viruses, modes of contamination and human transmission of the disease that are mainly linked to close contact with an infected animal or a patient suffering from the disease. The recommendations to contain the epidemic and challenges to achieve it are reminded. Keywords: Ebola, Outbreak, Virus, Hemorrhagic fever, Africa
Introduction The outbreak of Ebola virus disease (EVD) occurring in West Africa since December 2013 will mark the history – however brief – of the viruses. Occurring for the first time outside its original home – the Central African rainforest – this epidemic of EVD appears as the deadliest and longest of all those known so far. At this time (August 15th, 2014), more than 1,250 deaths have been reported, i.e. five times more than during the worst previous outbreak. In addition, its rapid propagation has led the World Health Organization (WHO) to declare on August 8th that EVD represent a “Public Health Emergency of International Concern” and urged the international community to take action to stop the spread. Finally, for the first time, in response to the severity of the situation, WHO agreed the use of experimental treatment against the EVD. Review Discovered in 1976 during two inaugural epidemics, both in Sudan and Democratic Republic of Congo (DRC), the Ebola viruses were responsible for 27 occurrences in Africa before the current outbreak of Guinea. This review aims to remind the characteristics of the different epidemics of EVD that were reported between 1976 and 2013. Correspondence: [email protected] 1 UMR 216, Mother and Child Facing Tropical Diseases, Institut de Recherche pour le Développement (IRD), Cotonou, Bénin 2 Université Paris Descartes, Sorbonne Paris Cité, Faculté de Pharmacie, Paris, France
Ebola viruses
The Ebola virus is, together with Marburg marburgvirus, native to East Africa, and belongs to the Filoviridae family (Table 1), whose newest member is Lloviu cuevavirus, recently isolated in Spain from bats [1-3]. Ebola viruses are RNA viruses whose genome encodes seven proteins [4,5]. They are of filamentary form, sometimes branched, with a diameter of 80 nm and a length of up to 14,000 nm (Figure 1). The protein shell encloses the tubular helical nucleocapsid. Surface transmembrane glycoproteins of the virion provide the binding and fusion with the cell membrane, and penetration into the cell. Glycoproteins are responsible for almost all the virulence, even though it does not explain all the pathogenicity [6]. Monocytes, particularly macrophages, are the first cells infected, triggering apoptosis in lymphoc
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