Ebola Viral Disease in West Africa: A Threat to Global Health, Economy and Political Stability

Omoleke, Semeeh Akinwale; Mohammed, Ibrahim; Saidu, Yauba

EVD is caused by one of five species of Ebola viruses, namely, Zaire (most fatal), Sudan, Tai Forest, Bundibugyo and Reston. 12 These five species, which were identified at different times, are genetically distinct and have caused outbreaks that differ in geographical spread and magnitude. In sub-Saharan Africa, most fatal outbreaks have been caused by Zaire ebolavirus, Sudan ebolavirus and Bundibugyo ebolavirus, with mortality ranging from 30-90%. 1 Zaire and Sudan ebolaviruses have caused repeated outbreaks in Central Africa since their discovery close to 4 decades ago while Bundibugyo ebolavirus was first identified in 2008 following a large outbreak in Bundibudyo, Uganda. 13 Prior to the current outbreak, little was known about EVD occurrence outside its traditional niche in Central Africa, except for a single reported case of human infection with the Tai specie resulting from contact with an infected chimpanzee in the Tai forest of Ivory Coast. 14 Initial molecular analysis of the isolates suggested that the outbreak, which has been ravaging West Africa for close to a year, was caused by a separate clade of virus from known ebolavirus strains from DRC and Gabon. 15 However, ensuing analysis indicated that the outbreak was caused by a strain that diverged from the Central African Zaire ebolavirus about a decade ago, rather than emergence of a separate clade of an endemic virus. 16 Although the outbreak was only officially reported to the World Health Organization on March 12, 2014 , epidemiologic findings through contact tracing suggest that the outbreak dated back to December 2, 2013 or possibly earlier. 15 The outbreak is traceable to a single index case (a 2-year old child in Gueckedou Prefecture of Guinea who died of the disease on Dec 6, 2013), whose family admitted to having hunted two species of bat-Hypsignatus monstrosus and Epomops franqueti, which are both reservoir species for Ebolaviruses. 17, 18 Subsequent spread of the disease occurred via close contacts with blood or body fluids of infected persons at family, community and/or hospital settings, and by the time the disease was recognized in March 2014, it was present in three countries. As at April 13, 2016 , total reported cases of EVD (confirmed, probable and suspected) were 28,652 from 10 countries; 15,261 cases were laboratory-confirmed and total deaths 11,325. 4 Virtually all the cases and deaths (99.87%) were from Guinea, Liberia and Sierra Leone, with the burden of disease highest in Sierra Leone and lowest in Guinea. 4 There were reported cases of importation beyond the African continent to Europe (3 cases in 3 countries: Spain, the United Kingdom and Italy) and North America (4 cases: United States of America) via international travels. 4 The WHO declared that the outbreak no longer constitutes a public health emergency of international concern on March 29, 2016, though the threat of re-emergence remains.