Ebola virus disease (EVD)

EVD summary^1,2

Pathogenic agent

Ebola virus (EBOV)

Location

Central Africa, West Africa

Transmission

EBOV spreads from wild animals to humans and by human-to-human transmission via contact with blood and body fluids or contaminated objects

Epidemiology

During the last half-century, there have been more than 40 outbreaks of EVD in Equatorial Africa
The largest outbreak so far caused over 28,000 infections and 11,000 deaths between 2013 and 2016
Case-fatality rate (CFR) is estimated at 40%–50%
The outbreak cost an estimated $2.2 billion to the economy of Guinea, Liberia, and Sierra Leone in 2015

Ebola virus disease (EVD) is a severe and often lethal disease caused by the Ebola virus (EBOV).¹ The virus is transmitted by direct human-to-human contact via blood and body fluids (ie, it is not transferred through a respiratory route like influenza)^1,3,4 and mainly affects adults, although infected children under the age of 5 years have a higher risk of dying from the disease.^1,3 The virus is also transmitted via the placenta and can result in fetal death.¹

During the last 50 years, there have been more than 40 outbreaks of EVD in Equatorial Africa.¹ The largest outbreak to date, from 2013 to 2016, caused over 28,000 infections and 11,000 deaths.¹

It is estimated that out of every 100 people who were diagnosed with EVD, 40–50 people died (a case-fatality rate of 40%–50%).¹ Aside from the devastating social impact, the epidemic had a significant effect on the economy in Guinea, Liberia, and Sierra Leone, costing an estimated $2.2 billion in the loss of gross domestic product (GDP) in 2015 alone.²

What characterizes EVD?

EVD usually begins with a fever and may progress to severe gastrointestinal symptoms, followed by abnormal blood clotting, unexplained hemorrhage, organ failure, and death.¹ A small subset of patients with lower viral load develop a robust immune response and recover, although the virus is likely to persist (remain alive and undetected) in their body, possibly in the central nervous system and the urinary and genital organs.¹

In these individuals, the virus can become active again and give rise to recurrent disease flare-ups.³ There are similarities between this chronic state of EVD and autoimmune diseases, which are typically characterized by unpredictable flare-ups of symptoms and a long-term impact on the health and well-being of those affected.⁵

EVD vaccines are urgently needed

The main strategy used to stop EVD outbreaks is the prevention of transmission between people in hospitals and the community.¹ Isolation of affected people and contact tracing are crucially important, and a ring vaccination strategy (contacts of infected people are identified and vaccinated) may be an effective solution.¹ An anti-EBOV vaccine was successfully tested using a ring vaccination study in 2016.⁶ Amid concerns about increasing transmission rates, accelerated development of anti-EBOV therapeutics and new and effective EVD vaccines is urgently required.^1,4

Jacob ST, et al. Ebola virus disease. Nat Rev Dis Primers. 2020;6:13.
Centers for Disease Control and Prevention (CDC). Cost of the ebola epidemic. Available at: https://www.cdc.gov/vhf/ebola/history/2014-2016-outbreak/cost-of-ebola.html [Accessed 27 Aug 2021].
Muñoz-Fontela C, McElroy AK. Ebola virus disease in humans: pathophysiology and immunity. Curr Top Microbiol Immunol. 2017;411:141–169.
Salata C, et al. Ebola virus entry: from molecular characterization to drug discovery. Viruses. 2019;11:274.
Rojas M, et al. Ebola virus disease: an emerging and re-emerging viral threat. J Autoimmun. 2020;106:102375.
Gsell P, et al. Ring vaccination with rVSV-ZEBOV under expanded access in response to an outbreak of Ebola virus disease in Guinea, 2016: an operational and vaccine safety report. Lancet Infect Dis. 2017;17(12):1276–1284.