The current Ebola outbreak has been termed as the largest outbreak in West Africa posing a threat to the public health not only locally, but also internationally. The latest outbreak began in late 2013 in Guinea and later dispersed in Liberia in March 2014. By August 14, 19 case of Ebola virus disease (EVD) have been reported in Liberal, which was 12 percent of 810 cases of the diseases reported globally (Arwady et al. 2015). In 1976, the outbreak was associated with 318 cases. However, the prevalence of the disease throughout 2014 revealed the lack of preparedness procedures and standard infection control in the national wide health care facilities. This can be articulated as the main predictor of the spread of the Ebola virus disease within some of the West African countries.
The molecular evolution of Ebola disease can be traced from the two viruses: ‘Ebolavirus' and ‘Marburgvirus' genera, which are both from the family of ‘Filoviridea. According to Caroll et al. (2013), the viruses are "nonsegmented, negative-strand RNA viruses that are, with few expectations, responsible for sever hemorrhagic fever outbreaks in Africa with high case fatality." When the viruses are present, the filovirus transmission occurs to humans when they directly contact with victims or get into contact with their body fluids. However, the case fatality rate in the epidemic environment varies between 25 percent and 90 percent (De La Vega M-A et al. 2015). The Ebola virus mutates to allow the virus to transmit through the air. Various studies suggest that the transmission and dissemination of virus are poor nursing strategies and participation of crowded place like burial (Arwwardy et al. 2015; Caroll et al., 2013; Lindblade et al. 2015).
According to De La Vega M-A et al. (2015), the ‘Marburgvirus' was first identified in the simultaneous development of disease in Marburg and Frankfurt in Germany, and Belgrade in Serbia five decades ago. The Marburg virus has a single virus species known as ‘Marburg Marburgvirus' that is made up of two difference viruses: Ravn and Marburg viruses that are about 20 percent divergent from each other (Caroll et al., 2013). However, the filoviruses have primarily originated from Africa except the Reston virus. The Ebolavirus was initially identified in 1976 in the Democratic Republic of Congo, which was formerly known as Zaire. A lethal Ebolavirus, known as ‘Zaire ebolavirus,' which consequently caused 15 cases of the outbreak with an average case fatality rate of 79 percent. Later, another Ebola outbreak emerged in Sudan caused by ‘Sudan ebolavirus.' The outbreak was associated with 284 cases and 151 deaths with an average case fatality rate of 63 percent (De La Vega M-A et al. 2015).
Another new Ebola species called ‘Tai Forest ebolavirus' was discovered in West Africa in 1994. The prevalence of the virus was surprising because West Africa was far from the country of origin. However, the spread of the virus was linked to the chimpanzee, in which a scientist contracted the virus through contact with this animal. Luckily, the patient received treatment in Switzerland and fully recovered as the only human who has survived the disease. In 2007, the disease was reported in East Africa where Ebolavirus killed 37 people in Uganda, and 149 cases were reported with case fertility rate of 25 percent.
Since Uganda outbreak, there has been only one documented outbreak in 2012 in the Democratic Republic of Congo. The virus that caused the disease genetically different species known as ‘Ebolavirus, Bundibugyo ebolavirus,' which has a case fatality rate of 38 percent. According to De La Vega M-A et al. (2015), this species is termed as the most lethal virus of Ebola in human. The most current new species of ebolavirus is the ‘Reston ebolavirus'. However, the most recent and threatening outbreak of Ebola (2014-2015) was caused by the ‘Ebolavirus, Zaire ebolavirus'. This virus is the lethal human pathogen and has contributed to the largest documented Ebola virus diseases and exponentially expanding with a period 34.8 days (Gire et al. 2015).
The genetic studies on the filovirus disease have indicated that the Ebola outbreak is of two different types. The first type includes how the first is transmitted to the population through direct person-to-person contact while the second type involves multiple forms of human transmission. When the virus is transmitted through the person-to-person contact, the molecular evolution of the virus seems to be minimal. The initial infection of human is perceived to be from getting contact with the infected body of mammals or nonhuman primates such as chimpanzees.
The recent studies have finally found that the natural reservoir of Marburgvirus and Ebolavirus is the Egyptian fruit bats, which were associated with the outbreak of the disease in Uganda (Carroll et al. 2013). From the sample of Ebola outbreak in 2014, there was one transmission from the natural reservoir and the person-to-person transmission. This outbreak was different to other outbreaks because the increasing human-reservoir exposure is anticipated to influence the growth and prevalence of this disease in West African (Gire et al. 2014).
References
Arwady, M. A., Bawo, L., Hunter, J. C., Massaquoi, M., Matanock, A., Dahn, B., & Monroe, B. (2015). Evolution of Ebola virus disease from exotic infection to global health priority, Liberia, mid-2014. Emerging infectious diseases, 21(4), 578.
Carroll, S. A., Towner, J. S., Sealy, T. K., McMullan, L. K., Khristova, M. L., Burt, F. J., & Nichol, S. T. (2013). Molecular evolution of viruses of the family Filoviridae based on 97 whole-genome sequences. Journal of virology, 87(5), 2608-2616.
De La Vega, M. A., Stein, D., & Kobinger, G. P. (2015). Ebolavirus evolution: past and present. PLoS Pathog, 11(11), e1005221.
Gire, S. K., Goba, A., Andersen, K. G., Sealfon, R. S., Park, D. J., Kanneh, L., & Wohl, S. (2014). Genomic surveillance elucidates Ebola virus origin and transmission during the 2014 outbreak. Science, 345(6202), 1369-1372.
Lindblade, K. A., Kateh, F., Nagbe, T. K., Neatherlin, J. C., Pillai, S. K., Attfield, K. R., & Kirking, H. L. (2015). Decreased Ebola transmission after rapid response to outbreaks in remote areas, Liberia, 2014. Emerging infectious diseases, 21(10), 1800.
