December 14, 2017

The Ebola Story

(To the many people we have lost. To the doctors and nurses we lost. To those who continue to fight this epidemic. Bless your soul.)

There had been a strange outbreak of a disease. Several lives had already been lost. In Gueckedou and Macenta, Guinea, on 10th, March, 2014, local health authorities alerted the Ministry of Health on a mysterious disease which had fever, severe diarrhoea and vomiting as its symptoms. It also had a high fatality rate. Eight patients were hospitalized in Gueckedou; three of them died, with reported deaths among relatives of the patients.  Around that time, in Macenta, several deaths were recorded including those of staff from a local health facility.  The Ministry of Health dispatched a team to the outbreak region on 14th, March. Meanwhile, Medecins sans Frontieres in Europe was notified, and on 18th, March, a team arrived to collect blood samples for two biosafety level four laboratories in Lyon, France and Hamburg, Germany, for virologic analysis.  The causative organism was identified as Ebola Virus (EBOV). The strain of this Ebola Virus showed a 97% identity to EBOV strains of Democratic Republic of Congo and Gabon, which occurred some ten years ago. [1]

Ebola Virus Disease (EVD) first appeared in 1976, simultaneously occurring in Nzara, The Sudan and Yambuku in Democratic Republic of Congo. EBOV got its name from a river near Yambuku and out the five species of EBOV, three have been associated with large outbreaks in human settlements in Africa. Outbreaks have occurred in Sudan, DRC, Republic of Congo and Uganda in time past. It is one of these species, the Zaire ebolavirus, which the current EBOV resembles. [2]

Ebola
As at July 2014

Early on in 2013, on 6th, December, a two-year old boy died. A week later, his mother, then, his three-year old sister and then, his grandmother died from similar symptoms as the boy. Researchers believe that the boy was the first victim of this current epidemic; Patient Zero.  Two mourners who attended the grandmother’s funeral picked up the virus. A health worker, also, carried it to another who died and the doctor who treated them died, too. They all infected relatives from other towns. [3]

The boy came from Gueckedou, a village in Nzerekore Region, southeastern Guinea. This region is renowned for its large weekly market, which brings traders from Sierra Leone, Liberia, Cote d’Ivoire and southern Guinea. It borders both Sierra Leone and Liberia. [4] Gueckedou would prove to be a perfect stage for what would later be the ‘’largest (Ebola) outbreak in history.’’

Sierra Leone, on 25th, May, confirmed its first case of EVD.  The patient had attended the burial of a traditional healer who had treated some patients from Guinea. Thirteen cases, all females who had also attended the healer’s burial, were traced and confirmed from that contact.  Gire et al. (2014) shows the Ebola epidemiology, relying on ninety-nine whole genome sequences, out of which seventy-eight were from affected persons in Sierra Leone. From those samples, genetic similarity suggests that a single transmission from the natural reservoir was followed by human-to-human transmission. Molecular dating places the common ancestor of all sequenced Guinea and Sierra Leone lineages around late February, 2014, some three months after the detection of the  earliest form of the EVD.[3]

An international team of researchers in August, 2014 revealed that the current outbreak was triggered by the two-year old’s chance contact with a single infected bat.  The team, comprising seventeen tropical diseases specialists, ecologists and anthropologists, spent three weeks researching in eastern Guinea. Their conclusion was that the EVD was initially spread by colonies of migratory fruit bats. [5]

EVD is part of what is called zoonotic diseases. It occurs when animal diseases are transmitted between animals and humans.  According to the US Centers for Diseases Control and Prevention, 60% of all human diseasing organisms are zoonotic including the HIV.  These infections (and later, diseases) are originally peculiar to animals but over time, they gain the ability to be transmitted to humans and finally, they are transmitted from human to human. These animal hosts become ‘’reservoir’’ host to the newly found human host and infect the human population when they get that ability. When these disease are appearing for the first time in a population or are previously known but are infecting at a faster rate, they are called emerging diseases. In the case of Ebola, a re-emerging diseases because it decreased in global incidence and more recently, there is a resurge in infection rate.

EBOV incredibly has a simple structure and it is with case fatality between 50% and 90%. It belongs to the family Filoviridae, same as Marburg.  A particle of EBOV is made of only six structural proteins.  The general mechanism of viruses is that when they into a host, they hijack the host system and command the host to replicate its (the viruses’) genetic material. EBOV has RNA as its genetic material. Most viruses are tissue specific but EBOV attack many tissues at the same time except the skeletal muscles and bones. It has a liking for the lining of blood vessels, particularly, those of the liver. The infected cells release new Ebola viral particles after eighteen hours of infection into the bloodstream and those go on to infect new cells. Symptoms begin to show 2-21 days after infection however Humans are not infectious until after the symptoms are exhibited.   At a point, the infected cells die, leading to multiple organ failure, and ultimately, death.  But EBOV makes errors in replicating its RNA, making it prone to mutations. [6] For example, Gire et al. (2014) found that the samples accumulated more than 395 mutations between the time the study began and June, with 50 mutations in the first month. There was, however, no sign that the mutation rate has contributed to the epidemic size.  Regardless, it poses a threat. ‘’ The longer we allow the outbreak to continue, the greater the opportunity the virus has to mutate , and it’s possible that it will mutate into a form that would be  even greater that it is right now,’’ Charles Chiu , an infectious-disease physician at the University of California was quoted in Nature. [7]

The WHO declared Nigeria Ebola-free after 42 days, twice the maximum incubation period of EBOV after the last infection was recorded. The WHO said the result was a ‘’world-class epidemiological detective work.’’ Nigeria reported its first case in July, taking down nineteen other people in the process. On 29th, August, Senegal confirmed its first case.  It has been declared as Ebola-free on 17th, October. Sporadic cases have since been recorded in the US and Spain.  Mali became the sixth in West Africa to confirm on 23rd, October.

At the time of this writing, 8,997 people have been officially sickened with EVD, out of which 4,493 have died. As the world grapples with the epidemic, efforts are being made to find a cure. That aspect was not highlighted in this presentation.

For a longer time to come, this epidemic will be a social scar, one that will remind us to respond to the issues of humanity with urgency. Never should a public health concern be the other’s problem. May those we have lost keep and rest well.

Notes

[1] Baize, S. et al. The New England Journal of Medicine.

http://www.nejm.org/doi/full/10.1056/NEJMoa1404505#t=article  Accessed on 21st, October, 2014 at 10:00 am.

[2] http://www.who.int/csr/don/2014_04_ebola/en/ Accessed on 21st, October, 2014 at 10:20 am.

[3] Gire, S.K. et al. Science Online http://www.sciencemag.org/content/345/6202/1369  Accessed on 22nd, October, 2014 at 12:00 pm

[4]  http://en.wikipedia.org/wiki/Gu%C3%A9ck%C3%A9dou Accessed on 21st, October, 2014 at 10: 30 am.

[5] John Vidal, The  Guardian. http://www.theguardian.com/society/2014/aug/23/ebola-outbreak-blamed-on-fruit-bats-africa Accessed on 22bd, October, 2014 at 9:00 am.

[6] Richard Preston, http://www.newyorker.com/magazine/2014/10/27/ebola-wars Accessed on 23rd, October, 2014 at 4:00 pm.

[7] Erika Ckeck Hayden, Nature Online http://www.nature.com/news/ebola-virus-mutating-rapidly-as-it-spreads-1.15777  Accessed on 23rd, October, 2014 at 4:00 pm.