Ebola virus belongs to the Filoviridae family can cause epidemics of haemorrhagic fever with high case-fatality rates. Ebolavirus first appeared in 1976 in 2 simultaneous Ebola outbreaks, in Nzara, Sudan, and in Yambuku, Democratic Republic of Congo. Ebola virus (EBOV) cause a severe viral hemorrhagic fever with high mortality in humans and nonhuman primates, killing up to 90% of those infected. The disease is characterized by widespread petechial hemorrhages, focal necrosis of the liver, kidney, and spleen, shock, and ultimately, death. Despite considerable effort, no animal or arthropod reservoir capable of sustaining the virus between outbreaks has been identified. Moreover, the pathogenesis of Ebola hemorrhagic fever is not fully understood, and no Ebola virus vaccine or effective therapies are currently available. Ebola virus (EBOV) is a select agent, World Health Organization Risk Group 4 Pathogen.
Based on antigenicity and the nucleotide sequences, the genus Ebolavirus is considered to have five species. Four of them have caused Ebola virus disease in human:Zaire Ebolavirus( ZEBOV / EBOV), Sudan eoblavirus (SUDV / SEBOV); Taï Forest ebolavirus (formerly Côte d'Ivoire ebolavirus, abbreviation:TAFV / CIEBOV) and Bundibugyo ebolavirus (BDBV / BEBOV). The last one Reston ebolavirus (REBOV / RESTV) have cause disease in nonhuman primates. But now, the Reston eoblavirus (RESTV) species, found in Philippines and the People's Republic of China, can infect humans, but no illness or death in humans from this species has been reported to date. Meanwhile, Bundibugyo ebolavirus (BDBV),Zaire ebolavirus (ZEBOV), and Sudan eoblavirus (SUDV) have been associated with large Ebola virus Disease / Ebola hemorrhagic Fever (EVD / EHF) outbreaks in Africa, whereas Reston eoblavirus (RESTV) and Taï Forest ebolavirus (TAFV) have not.
Picture below has shown the geographic distribution of Ebola virus disease outbreaks in human and animals in 2014. (From WHO)
After infected with Ebolavirus for 1-2 weeks, patients will suffer fever, asthenia, diarrhoea, abdominal pain, headache, arthralgia, myalgia, sore throat, dysphagia, and conjunctivitis. These are type Ebola virus symptoms after Ebola virus infection. One week later, they will get a rash, and subsequently the haemorrhagic complications, which usually result in death in 10 days. For the survivors, severe asthenia, hearing loss, ocular signs may affect them for 2 weeks to 2 months until recovery. No vaccine exists and there is no FDA-approved therapeutics. Thus, Ebola virus has been considered as a biosafety level 4 pathogen. The case fatality rate of Ebola virus disease varies depending on the ebolavirus species involved, with Ebola virus (EBOV) having a case fatality rate of 60-90%, whereas Sudan ebloavirus (SUDV) and Bundibugyo ebolavirus (BDBV) show lower average case fatality rates of 40-60% and 25%, respectively. Taï Forest ebolavirus (TAFV) has caused only a single severe infection in humans; therefore, the lethality rate is unknown.