3. The 2014 West African Ebola outbreak

believed to be transmitted by bats being the primary reservoir mostly through body fluid or contact to humans and other primates. The virus can penetrate mucosal membrane to infect various cells in the body including macrophages, monocytes, dendritic cells, etc. and spread into the circulatory and lymphatic systems damaging blood vessels leading to haemorrhage. Though no approved standard treatment is available for the disease, it has been managed with certain antiretrovirals and supportive treatments such as rehydrating solutions for maintaining fluid and electrolyte balance as well as treatments against secondary infections. Thus, the availability of a standard approved drug is one of main concern in recent time following the 2014 fatal outbreak. More so, since this disease is sporadic and usually emerges as an outbreak, effective control is usually difficult as diagnosing viraemia is usually challenging. Also, no existing vaccine is available against the disease. Following the introduction of experimental drugs and vaccines during the 2014 West-Africa Ebola outbreak which contributed to its control [3], it has been of interest to know the progress so far and efforts that are been laid to ensure that these drugs and vaccines are licensed in future. Hence, this chapter will focus on the progress towards the provision of diagnostic tools, and availability of specific treatments and vaccines. However, an understanding of the aetiology and pathogenesis of Ebola virus disease is necessary so as to expose possible drug targets as well as various vaccine candidates

This viral disease emerged around 1976 with the first outbreak in the northern part of DRC, formerly known as Zaire which affected about 318 individuals with a mortality rate of 88% [1]. Almost at the same period and year, another outbreak emerged in southern Sudan with 284 cases killing about 150 individuals (53%) [4]. In 1976, a case of the infection of the Sudan virus was identified in England but there was no casualty [5]. The following year in 1977, a case was reported in DRC which the individual died. By 1979, there was reoccurrence of an outbreak in Southern Sudan which affected 34 individual with a 65% mortality rate. The disease was absent for about 2 decades before re-emerging in Gabon and Ivory Coast in 1994, with a mortality rate of 60% in Gabon [6]. The disease reoccurred in Gabon in 1996 and 1997 [6], and again in DRC in 1995 [7]. In 2000, an outbreak was reported in Uganda with over 80% mortality while the following year, another outbreak was reported in Gabon with 53% and 82% mortality rate respectively [8]. Since then, there has been reoccurrence of outbreaks in DRC between 2001 and 2008 [9] and in Uganda between 2007 and 2012 [10]. In 2012, there was another outbreak in DRC with a fatality rate of about 40% [11]. In 2014, the largest outbreak was recorded in DRC [12] and West Africa [13] that spanned across various countries including United State, Spain, Mali, Senegal and Nigeria [14].

It should also be noted that some non-human primate infections have also occurred. The first to be observed was in the United States between 1989 and 1990 [15] followed by another outbreak in Italy in 1992 which were related to the importation of monkeys from the Philippines [16]. In 2008, cases of respiratory and porcine reproductive syndrome in sows and piglets caused by the Ebola virus were observed in China and Philippines with high mortality. Animal farmer workers who were in contact with the virus became infected but the infection was

for a better management of the disease.

130 Current Topics in Tropical Emerging Diseases and Travel Medicine

2. The origin and epidemiology of Ebola virus disease

asymptomatic and no casualties were recorded [17].

The first trace of the infection was in Guinea in December 2013 which subsequently spread to Liberia and Sierra Leone. In 2014, the world recorded the largest Ebola virus outbreak in West Africa particularly in Sierra Leone, Guinea, and Liberia, with over 7178 infected cases 3338 deaths amounting to a mortality rate of 51% as of 1st October, 2014 [18]. Also, the disease spread to other countries including Nigeria and USA. [18]. In August 2014, the epidemic was declared by the World Health Organization (WHO) as a public health emergency of international concern [19]. By September 2014, the fatality rate of infected individuals was about 70.8% in Liberia, Guinea, and Sierra Leone. About 20 cases were report in Nigeria which originated from a traveller from Liberia in July 2014 with a fatality rate of 45.5%. As of 23rd October, 2014, about 450 health care personnel were known to be infected with Ebola virus of which 244 died [20]. In October 2014, two imported cases with one death, as well as two locally acquired cases from health care workers were identified in the United States. By November 2014, a cumulative total of 20,000 Ebola cases were reported in the West Africa outbreak including 5740 cases from Guinea, 9890 from Liberia and 5000 from Sierra Leone [20] killing over 11,300 individuals within the course of 2 years.
