The Dangers of the New Ebola Outbreak

“How Bad is Ebola?” in 4 Minutes

Fruit bat. Photo by José Zajaczkowski on Unsplash.

On April 23rd, health authorities in the Democratic Republic of the Congo declared a new Ebola outbreak in the Mbandaka city of the Equateur Province. There have been only three reported deaths so far, but already over four hundred contacts were identified and are being monitored by local responders. Although the outbreak appears to be contained, it still poses a significant danger if not dealt with accordingly.

The Ebola virus disease, also known as Ebola hemorrhagic fever, first emerged in 1976 in two simultaneous outbreaks. One in South Sudan and the other in the Democratic Republic of the Congo (DRC) — the former Republic of Zaire. The latter took place in a village near the Ebola River, which gave the virus its name. Together, both outbreaks killed over four hundred people and, ever since then, multiple Ebola epidemics have taken place across Africa.

The natural reservoir of the Ebola virus has yet to be identified, but it is generally believed that the virus originates from fruit bats, and that new outbreaks result from zoonotic spillovers — that is, through contact of humans with an infected animal, including the recent outbreak in Equateur.

Although these events are very rare, the virus is then easily transmitted among humans, with each patient expected to infect between one to two persons, if precautions are not taken to prevent the spread of the disease. The virus transmission occurs through direct contact between open skin wounds or mucous membranes, such as the mouth and eyes, and the body fluids of an infected person (e.g., saliva, vomit, blood or feces). That is why people in close contact with patients or Ebola victims like healthcare workers and morticians are at a higher risk of becoming infected. Especially, if they lack personal protective equipment.

Although most human cells can be infected, the Ebola virus is particularly fond of a subset of white blood cells (monocytes, macrophages and dendritic cells), and viral replication within these cells will trigger the onset of symptoms, one to three weeks after exposure.

For the first three days after onset, Ebola patients present with flu-like symptoms (fever, headaches, sore throat, muscle and joint pain) — which makes early diagnosis difficult since these are the same symptoms as many other tropical diseases like malaria and typhoid fever. In the meantime, the virus has disseminated through the bloodstream and begins to infect secondary targets.

Patients then progress within the first week into severe gastrointestinal symptoms such as nausea, vomiting, abdominal pain and high-volume diarrhea, as the virus targets the mucosa of the stomach and intestines. Diarrhea in turn leads to dehydration, which causes low blood pressure (hypotension).

Going into the second week, patients either recover, often with long-lasting sequelae (e.g., muscle and joint pain), or begin to develop complications. These include coagulation disorders (coagulopathy) and multi-organ failure due to a dysregulated immune response, which affects especially the liver and kidneys. As a result of poor coagulation and damage caused by the virus to the endothelial cell lining of the blood vessels, some patients will also suffer from internal and external bleeding. In these cases, blood is seen in nosebleeds, skin hematomas, vomit, stools and even the eye sclera.

At the late-stage of infection, patient may also experience hiccups, which for unknown reasons, are associated with hemorrhagic fevers — especially Ebola. This was one of the clues that alerted doctors and researchers to the West Africa outbreak of 2014–2016, which killed over eleven thousand people. The largest Ebola epidemic in history.

Ebola viral particle. Transmission electron micrograph by Cynthia Goldsmith at the CDC Public Health Image Library (#1832).

In severe Ebola cases, the loss of blood volume (hypovolemia), as a consequence of dehydration and bleeding, combined with multi-organ failure, may eventually cause the death of the patient from hypovolemic shock. Supportive care like fluid therapy and blood products, as well as the recent monoclonal antibody drugs developed in 2020, are extremely important to ensure survival. However, Ebola is currently one of the most lethal viral diseases in the world, alongside Marburg virus disease, with an average case fatality rate of roughly 50% — meaning that one in two infected dies.

This rate varies widely between outbreaks. It has been as low as 25% and as high as 90%, possibly due to differences in population immunity and also depending on which of the four human-infectious strains of Ebola virus caused the outbreak. But perhaps most importantly, virus lethality is exacerbated by armed conflicts and unstable healthcare systems.

These factors played a key role in the recent devastating DRC outbreak of 2018–2020, since it was extremely dangerous for the World Health Organization (WHO) staff and healthcare workers to provide aid in an active war zone. Dangerous to the point where four Ebola healthcare workers were killed at the hands of rebel militias in 2019. When the outbreak was over, more than two thousand people had died from Ebola, making it the second largest Ebola outbreak in history — only surpassed by that of West Africa. At the time, both these outbreaks were declared Public Health Emergencies of International Concern by the WHO.

Today, as the Democratic Republic of the Congo successfully launches a preventive vaccination campaign, it is important to recall the dangers of an unrestrained outbreak so that we can ensure these events do not happen again.

P.S. Update on July 7th: Thanks to the swift response led by national emergency teams and the WHO, the DRC declared the end of the Ebola outbreak on July 4th. There was a total of four confirmed cases and one probable case — all of them fatal.

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Gil Pires

Gil Pires

Junior Consultant | MSc in Biotechnology