The Ebola Virus

Podcast Transcript

In 1976, a mysterious and deadly illness appeared almost simultaneously in Sudan and Zaire.

It killed with frightening speed, baffled doctors, and was eventually named after a river few people had ever heard of: Ebola.

Since then, it has caused some of the most feared outbreaks in modern history, while also driving major advances in medicine, vaccines, and global public health.

Learn more about the deadly Ebola Virus and the efforts to fight it on this episode of Everything Everywhere Daily.

The very word Ebola strikes terror into some people, and for good reason. Ebola is one of the deadliest diseases on the planet. It isn’t just that it has an incredibly high mortality rate, which it does, but it’s that the way victims die is horrific and painful.

Technically, Ebola is not a single virus. It is a group of closely related viruses in the genus Ebolavirus. The one most people mean when they say “Ebola” is Zaire ebolavirus, the deadliest and most historically important member of the group.

Ebola is rare compared with influenza or measles, but it has a reputation unlike almost any other virus. When it does break into human populations, it can kill a very high percentage of those it infects.

Ebola viruses are categorized as filoviruses, from the Latin word for “thread,” because under an electron microscope they often appear as long, filament-like strands. Their natural reservoir remains unknown with complete certainty, but fruit bats are considered the leading suspect, and outbreaks often begin after some contact between wildlife and humans.

Once infected, Ebola does not spread like measles or influenza. It is not mainly an airborne respiratory virus. It spreads through direct contact with the blood or bodily fluids of someone who is sick or has died from the disease, or through contaminated objects such as needles, bedding, or medical equipment.

This is one reason Ebola can devastate families, health workers, and burial teams, while still being much less contagious in casual public settings than other airborne viruses.

The incubation period is usually between 2 and 21 days. The CDC describes the early illness as “dry” symptoms, including fever, aches, pains, and fatigue. As the disease progresses, it can move into “wet” symptoms such as vomiting, diarrhea, and unexplained bleeding.

The bleeding is what made the older term “Ebola hemorrhagic fever” famous, but it is not always the dominant symptom. The real danger is often a combination of massive fluid loss, shock, organ dysfunction, immune-system overreaction, and problems with blood clotting.

Severe cases can include abdominal pain, rash, red eyes, confusion, kidney and liver impairment, internal bleeding, and bleeding from the gums, nose, or injection sites.

Ebola is lethal, but the exact lethality depends on the strain, the outbreak, and the quality of care. The WHO gives an average Ebola disease case fatality rate of around 50 percent, with past outbreaks ranging from about 25 percent to 90 percent.

Ebola is one of the deadliest diseases in the world, but it is not the deadliest disease. On average, it has a higher mortality rate than smallpox, but it is less than rabies, which has a 100% fatality rate. Rabies, however, is preventable after exposure if treated in time.

Compared with other viruses, Ebola sits in an unusual position. It is far deadlier than seasonal influenza, measles, or most coronavirus infections on a case-by-case basis, but it is much less efficient at spreading through the air. Measles is one of the most contagious human viruses and spreads through breathing, coughing, and sneezing, while Ebola normally requires contact with infectious fluids.

In terms of lethality, Ebola is closer to the Marburg virus, another filovirus, for which the WHO reports an average fatality rate around 50 percent and past outbreaks ranging from 24 percent to 88 percent.

We don’t know when the Ebola Virus first came into existence. It has probably existed for hundreds, if not thousands, of years, primarily being transmitted by animals. If there was transmission to humans, it probably occurred in isolated communities or individuals and swept through quickly given its high mortality rate.

The Ebola virus was first discovered in 1976 when two simultaneous outbreaks of hemorrhagic fever occurred in two neighboring locations, one in southern Sudan and one in northern Zaire. The virus was first isolated from a woman named Myriam Louise Ecran, a 42-year-old Belgian nursing sister working at the Yambuku Mission Hospital, who died caring for people with the unknown disease.

When it came time to name the virus, the international team of scientists faced a deliberate choice. When the commission considered naming it the “Yambuku virus,” researchers Karl Johnson and Joel Breman pointed out that naming the Lassa virus after the Nigerian village where it was discovered had brought stigma to that community.

Johnson suggested naming the new virus after a nearby river instead. There was briefly a push to name it after the Congo River, the deepest river in the world, but another virus with a similar name, the Crimean-Congo hemorrhagic fever virus, already existed. So scientists looked at a map pinned on the wall and found a nearby river called Ebola

There is some irony in the name. The Belgian name for the river, “l’Ebola,” is actually a corruption of the indigenous Ngbandi name “Legbala,” meaning “white water” or “pure water.”

Co-discoverer Dr. Peter Piot later acknowledged in his memoir that the map they used was inaccurate and that the Ebola River was not actually the closest river to Yambuku, but by then the name had already stuck.

There are five subtypes of the Ebola virus: Zaire, Sudan, Bundibugyo, Tai Forest, and Reston, each named after the location in which it was first identified. The first three subtypes have been associated with large outbreaks in Africa. The Reston subtype is found in the western Pacific and, while highly dangerous to non-human primates, is not known to cause illness in humans.

The 1976 outbreak in Zaire was the first and set the template for the outbreaks that followed. The virus spread rapidly through the Yambuku Mission Hospital, where unsterilized needles were reused, infecting staff and forcing the facility to close after multiple deaths.

Many infected people fled to their home villages out of fear, seeking treatment from traditional healers, which helped spread the disease further. That first outbreak resulted in 318 cases and 280 deaths.

In 1995, an outbreak began among charcoal makers in the forests near the city of Kikwit in the Democratic Republic of the Congo. It led to 315 cases and 250 deaths. The virus spread through families and hospitals but was eventually stopped when healthcare staff began using face masks, gloves, and gowns.

In 2000 in Uganda, there were 425 Ebola cases and 224 deaths. The outbreak began in Gulu and spread to other districts. The strain involved was the Sudan virus, and the median age of those infected was 27, though nearly 15 percent of cases were children under five.

The largest outbreak in history came between 2013 and 2016. That outbreak in West Africa was the largest since the virus was first discovered in 1976, with more cases and deaths than all previous outbreaks combined. It started in Guinea and quickly spread to Sierra Leone and Liberia.

By July 2014, it had reached the capital cities of all three countries, and in August 2014, the WHO declared it a Public Health Emergency of International Concern.

The disease ultimately spread to seven additional countries, including the United States, Spain, and the United Kingdom. In total, there were 28,652 cases worldwide and 11,325 reported deaths across 10 countries.

A second major DRC outbreak between 2018 and 2020 was also significant, occurring in an active conflict zone and resulting in more than 3,000 cases, making it the largest outbreak in that country’s history.

As recently as September 2025, the DRC Ministry of Public Health declared an Ebola outbreak in the remote Kasai Province, which was contained by December 2025 with 53 confirmed cases and 45 deaths. It was the sixteenth Ebola outbreak in the DRC since 1976.

The 2026 Ebola outbreak is a fast-moving outbreak caused by the Bundibugyo variant, centered in the eastern DRC and now involving Uganda.. As of the recording of this episode, the World Health Organization reported over 800 suspected cases and over 100 suspected deaths in DRC.

So, just how worried should you be about the Ebola Virus?

The short answer is, not very. People should be very concerned at a public-health level, especially in the affected parts of the Democratic Republic of the Congo and Uganda, but ordinary people in countries far from the outbreak should not be personally panicked. For most people outside the outbreak region, the risk is extremely low.

It might sound very odd to say, but because Ebola is so deadly, the odds of it ever spreading like the Black Death are very remote. It simply kills those infected too quickly for it to spread rapidly. Likewise, because it has to be spread via fluids, it is relatively easy to protect against using modern medical precautions.

One concern that has been expressed is a fear of Ebola becoming an airborne virus.

It is theoretically possible, in a very broad sense, that viruses can mutate, but it is extremely unlikely that Ebola would naturally become airborne in the way measles, chickenpox, or influenza do.

For Ebola to become truly airborne, it would have to change a lot. It would need to replicate well in the upper respiratory tract, be shed in large amounts from the nose, throat, or lungs, survive in tiny suspended droplets, and still infect another person after being inhaled.

Those are not small tweaks. They would require a major change in the virus’s biology, meaning the kinds of cells and organs it prefers to infect. At that point, it wouldn’t really be Ebola anymore.

There is actually some good news on the Ebola front.

The 2013–2016 epidemic was the largest Ebola outbreak to date and prompted numerous partners from the public and private sectors to combine efforts and resources to develop a vaccine as quickly as possible.

The leading candidate was originally developed by experts at the Public Health Agency of Canada and later licensed to Merck. It uses a genetically engineered version of the vesicular stomatitis virus, an animal virus that primarily affects cattle, to carry an Ebola virus gene insert, which trains the immune system to recognize Ebola.

The vaccine underwent preclinical testing and then moved through Phase 1, 2, and 3 clinical trials. A key trial in Guinea in 2015 used a “ring vaccination” strategy, vaccinating the immediate contacts of confirmed cases and the contacts of those contacts, and the results were striking. Of the people vaccinated immediately, there were zero cases of Ebola in the weeks following vaccination.

In November 2019, the European Commission granted a conditional marketing authorization for the vaccine, now sold under the brand name Ervebo. The WHO prequalification followed within 48 hours, the fastest vaccine prequalification process in WHO history. It was then approved in the United States in December 2019.

Ervebo was tested in approximately 16,000 individuals across multiple clinical studies in Africa, Europe, and the United States before being approved. Its limitations are notable, however: it specifically protects against the Zaire ebolavirus strain, which is the most dangerous, but does not protect against the other strains.

Ebola is bad, no doubt about it. I wouldn’t wish it on my worst enemy. Public health organizations should certainly be worried about it.

However, it isn’t something most people should worry about unless they live in Central or Western Africa.

The good news is that if progress on vaccines continues, maybe in the future, Ebola is something that no one anywhere will ever have to worry about again.