I Guess We Have to Talk About Ebola
(Because this topic being what it is, I think it’s probably important to remind readers that I’m a Global Health Epidemiologist and Professor with the Interdisciplinary School of Health Sciences at the University of Ottawa. I’m not a direct researcher of Ebola, but developing some familiarity with the disease is unavoidable in my overall work with the health care systems of lower-income countries.)
The life of an epidemiologist in the 2020s is never boring. Last week, the big news was hantavirus. Today, it’s Ebola. If you don’t know, there is a significant Ebola outbreak happening right now in Africa. As of May 20–22, WHO and ECDC reports indicate that there are approximately 600 cases, 139 deaths, 51 laboratory-confirmed cases in the Democratic Republic of the Congo (DRC), and 2 confirmed imported cases in Uganda. The actual numbers may be higher because surveillance in conflict zones is difficult. WHO officials have said the virus may have circulated undetected for months before recognition.
What is Ebola?
Before I get into an analysis of the current situation, let’s go over what we know about Ebola.
Ebola virus disease is a severe viral hemorrhagic fever caused by several Ebola virus species. It is characterized by fever, weakness, gastrointestinal symptoms, and in severe cases, bleeding, shock, and multi-organ failure. Case fatality rates vary widely by species and outbreak conditions, ranging from roughly 25% to 90%.
Ebola was first recognized in 1976 during simultaneous outbreaks in the DRC (then Zaire) and Sudan. The virus was named after the Ebola River near one of the original outbreak sites. Historically, outbreaks were relatively small and localized in remote Central African regions. The largest outbreak occurred in West Africa from 2014–2016, mainly affecting Guinea, Liberia, and Sierra Leone. That epidemic caused more than 28,000 cases and over 11,000 deaths, and demonstrated how Ebola can spread rapidly in urban settings with weak healthcare infrastructure.
There are at least six types of Ebola virus:
1. Zaire ebolavirus
- The deadliest and most common cause of major outbreaks.
- Responsible for the 2014–2016 West African epidemic.
- Existing vaccines work primarily against this species.
2. Sudan ebolavirus
- Causes periodic outbreaks in East Africa.
- No widely licensed vaccine yet.
3. Bundibugyo ebolavirus
- First identified in Uganda in 2007.
- Causes somewhat lower fatality rates on average.
- The current 2026 outbreak involves this species.
4. Taï Forest ebolavirus
- Rare; only one known human case.
5. Reston ebolavirus
- Found mainly in pigs and monkeys in Asia.
- Can infect humans but has not been shown to cause serious disease in people.
6. Bombali ebolavirus
- Identified in bats.
- No confirmed human cases (yet).
Natural Reservoir
A natural reservoir for disease is any living host, organism, or environmental habitat in which a pathogen naturally lives, multiplies, and survives. These reservoirs act as a continual source of infection, allowing the disease to persist in nature usually without causing fatal illness to the host itself.
The best evidence suggests that fruit bats are the natural reservoir hosts for Ebola virus. Suspected bat species include hammer-headed bats, straw-colored fruit bats, and little collared fruit bats. It’s important to note that as natural reservoirs, bats may carry the virus without becoming seriously ill.
Humans and other mammals are thought to become infected through contact with infected wildlife, handling/eating/preparing bushmeat handling or generally messing with infected animal carcasses. Nonhuman primates like gorillas and chimpanzees are usually victims, not reservoirs. So don’t victim-blame, people.
Transmission
Ebola spreads through direct contact with bodily fluids, i.e. blood, vomit, diarrhea, sweat, and semen. You know, all the good stuff.
You can also get it from contaminated needles or surfaces, and from contact with infected corpses during burial rituals, which is a particularly cruel route for communities struggling with both epidemic and grief.
** It does NOT spread efficiently through the air like measles or COVID-19.
Transmission risk is highest among caregivers, household contacts, and healthcare workers without proper PPE (personal protective equipment).
Importantly, patients are generally not contagious before symptoms begin… which brings us to the incubation period, which is 2–21 days (most commonly 8–10 days). This means that if you are on an airplane with an Ebola-infected person who is NOT symptomatic, your risk of acquiring the disease is negligible.
Now, there is ongoing scientific discussion about whether very early symptomatic people may occasionally transmit before they fully recognize they are sick. But “very early symptomatic” is not the same thing as asymptomatic. Got it? So, asymptomatic Ebola transmission is not considered a driver of outbreaks.
So What Are Those Symptoms?
Typical symptoms include fever, headache, fatigue, muscle pain, vomiting, diarrhea, and abdominal pain. Severe disease can progress to liver and kidney dysfunction, shock, internal and external bleeding, neurologic complications, and of course death.
Bleeding occurs in some, but not all, patients. This is why Ebola gets the reputation as a “bleeding disease.”
Remember, people with Ebola virus disease are generally not considered contagious before symptoms begin. Transmission risk rises once symptoms begin, especially when the patient develops fever, vomiting, diarrhea, bleeding, or anything involving the production and leakage of large amounts of bodily fluids.
Historically, virtually all confirmed transmission events have involved direct physical contact, caregiving, unsafe burial practices, or contact with bodily fluids.
But please note: once symptoms start (even mild fever or malaise) the risk calculus changes rapidly. Someone in the earliest symptomatic phase may still look relatively well but could already be infectious, especially with close physical contact.
Vaccines and Treatment
Treatment for this disease is mainly supportive, i.e. the health professionals will treat the symptoms and give the patient the best chance possible of fighting it off themselves. This includes things like IV fluids, oxygen, and maybe painkillers and some drugs to treat secondary infections. For Zaire ebolavirus specifically, monoclonal antibody therapies have improved survival substantially.
The one licensed Ebola vaccine, called Ervebo, is meant for Zaire ebolavirus, against which it is high effective. But its protection against other Ebola species appears limited. Some animal studies suggest partial cross-protection against Bundibugyo and Sudan strains, though no strong human evidence yet exists.
Why is Ebola so Dangerous and Scary?
Well, duh, if you get it, there’s a high chance of it killing you. And they way that it does so can get pretty ugly. But that’s true for lots of diseases. What’s particularly distressing about Ebola is its outbreaks can get really serious when healthcare systems are weak, there’s not enough PPE to go around (so hospitals end up amplifying transmission), or when mistrust of authorities prevents citizens from taking the right and rational precautions. The virus can therefore overwhelm fragile health systems (and places with poor information infrastructure) very quickly.
This is why it seems to ravage low-income countries the most.
Why Is The Current Outbreak So Important?
All Ebola outbreaks are important because lots of people get sick and die. But from the perspective of global health, I want to make nine points about the current situation.
- 1. It involves the Bundibugyo strain
Because the current DRC outbreak involves Bundibugyo ebolavirus (BDBV), there is no highly effective vaccine. This means we can’t just ring-vaccinate everyone and contain it that way, as we could in a more common Zaire Ebola outbreak. This makes the situation a tad scarier.
- 2. The outbreak may have circulated undetected for months
Delayed detection means that transmission chains are already established, the contacts of exposed people are now really hard to trace because both exposed and infected people may have already travelled widely before quarantine and isolation measures began.
In other words, the true number of cases may already be much larger than official counts suggest.
- 3. Cross-border spread has already occurred
It started in the DRC, but is now in Uganda. It has already crossed one international border. Mind you, I myself have crossed that border in a, shall we say, less than official manner. It ain’t that hard.
Cross-border transmission increases the complexity of surveillance, contact tracing, and public communication, and also requires coordinating multiple health ministries. Regional mobility in Central and East Africa is high, making containment harder.
- 4. Urban transmission is especially dangerous
Historically, Ebola outbreaks in remote rural areas have been easier to contain than outbreaks involving densely populated cities.
Urban outbreaks create more contacts, faster movement, more healthcare exposure, and, of course, more opportunities for international travel. The 2014–2016 West African epidemic demonstrated how quickly Ebola can escalate once cities are involved.
We are already seeing cases near urban centres.
- 5. The affected region is politically unstable
The Eastern DRC has armed conflict, mass displacement, weak infrastructure, and chronic insecurity: the perfect recipe for undermining outbreak control. This is because healthcare workers may not safely access communities, supply chains break down, roads become impassable, and of course mistrust of authority increases. Previous Ebola outbreaks in conflict zones have shown that violence and misinformation can dramatically worsen transmission.
- 6. Healthcare systems are fragile
Ebola is dangerous partly because it amplifies inside healthcare settings. Several healthcare worker infections have already been reported.
- 7. Ebola is highly lethal
Of course, this is what really scares most of the world. Bundibugyo outbreaks historically have shown case-fatality ratios around 25-50%. Yikes.
- 8. The world is more connected now
Those in my profession have been preaching this fact for years. It is now possible to contract a disease in Tokyo, board a plane, and land in New York before the incubation period is over. In the history of people and disease, we are in unprecedented epidemic times. This is both a good and bad thing.
The bad is obvious: more people encroaching into unexplored niches where nasty bugs lay in wait, more people travelling the world at incredible speeds, and climate change making reservoir behaviours more unpredictable.
But there is also good. We have global disease surveillance, so that a novel disease should not arrive at our doorsteps without significant forewarning. We have the ability to move people, expertise and resources to any point on the planet to quash outbreaks as they are detected. And we have the ability to flood areas with proper information to help those on the ground self-contain and self-care.
- 9. But this is NOT another COVID-style pandemic
I cannot stress this enough. While this is an international emergency, in the sense that multiple countries in the Central African region must be on alert, this disease does not pose a pandemic threat, in the way of COVID or the flu.
This is because: (a) Ebola transmission requires close contact with bodily fluids, (b) asymptomatic spread is not thought to be a major driver,
and (b) visibly ill patients are usually the most infectious, so they’re not slipping by screening protocols.
These facts make classic public health tools like isolation, PPE, contact tracing, and safe burials much more effective than they were against COVID.
So, as with the recent hantavirus story, I advise people in North America and Europe not to get too worked up over this crisis. It’s a serious event for residents of Central Africa, who need and deserve our support. But it is highly unlikely that it will result in any onward transmission in the West.
