WS MoreOrLess: Ebola

Summary

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More or Less – “Ebola: The Truth Behind the Numbers”

BBC Radio 4 | Air Date: August 10, 2014 | Host: Ruth Alexander

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Episode Overview

In this episode, Ruth Alexander and the More or Less team investigate the widely reported statistic that Ebola kills "up to 90% of those infected." Prompted by a listener question, the episode breaks down what this statistic actually means, digs into country-by-country fatality rates during the 2014 West African outbreak, and puts the risks and transmission of Ebola in global context. The episode separates cinematic myth from practical risk, underscoring the real facts behind headline numbers.

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Key Themes and Discussion Points

1. Understanding Ebola Fatality Rates

• Media and Public Fear
  The episode opens with a litany of dramatic media statements about Ebola’s deadliness, highlighting widespread anxiety.

• Listener Question:
  Max Cousens asks for clarification on the oft-quoted “90% fatality rate” for Ebola, wondering about its context and accuracy.

• Defining Case Fatality Rate (CFR)

  • James Fletcher (01:47): Explains CFR as "the number of people who die from an illness divided by the number of people who are diagnosed with that illness."

The “90%” Statistic Debunked

• Maimouna Majumda, Biostatistician and Epidemiologist, MIT (02:15):

  "That 90% figure actually comes from one outbreak of Ebola, which took place in the Congo between 2002 and 2003. So it's the highest rate we've ever seen. We've also seen CFRs much lower than that in previous outbreaks..."

• Key Contexts:
  • The 90% CFR is an outlier, not the norm.
  • The cumulative average since 1976 is 60–65%.
  • In the 2014 West Africa outbreak, as of this episode, the CFR is about 54% (subject to change).

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2. Variation in Fatality Rates by Country

• James Fletcher (03:10):
  Detailed breakdowns of the CFR in affected countries:

  • Guinea: 73%
  • Liberia: 55%
  • Sierra Leone: 41%
  • Nigeria: 11% (very few cases; conclusions limited)

• Ruth Alexander (03:42): Notes the "big differences" between countries.

Why Do CFRs Vary?

• Majumda (03:49):

  "The two biggest factors that are influencing case fatality rate are first, familiarity with the disease... and the second is availability of resources to contain, prevent and treat..."

  • Emphasizes West Africa's lack of prior Ebola experience and limited resources.
  • Advocates reporting the cumulative historical average, not the extreme outlier.

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3. How Contagious is Ebola, Really?

• James Fletcher (04:53):
  Discusses transmission risk, contrasting Ebola with more common infectious diseases:

  • Ebola is not easily transmitted: It spreads via direct contact with body fluids, not via the air.
  • Diseases like measles and flu are much more contagious but can have a lower CFR.

• Notable Comparison:

  • Measles: Approx. 10% CFR where health care is poor, but resulted in 120,000 deaths in 2012—far more than Ebola, due to ease of transmission.

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4. The Fear of Global Spread

• Ruth Alexander (05:47):
  Addresses worries about the virus reaching the US, UK, and beyond. Airlines have suspended flights, and controversial figures like Donald Trump call for extreme containment measures.

• James Fletcher (06:22):
  Dismisses “rational calculation of risk” at such panic levels, stressing that while more deaths will occur in West Africa, a global outbreak is “pretty unlikely.”

Expert Perspective:

• Dr. Adam Kucharski, Infectious Disease Epidemiologist (06:44):

  "In theory, Ebola is a controllable disease, so we're very unlikely to see a major outbreak in the UK, for example. The reason being that Ebola, you don't become infectious until you're symptomatic..."

  • Contrasts Ebola's transmission to airborne diseases, emphasizing controllability.

What Would It Take for Ebola to Spread Globally?

• Majumda (07:25):
  Lays out the highly specific and improbable chain of events required for Ebola to spread to places like the US:
  • Infected, but not yet symptomatic person boards a plane (very unlikely)
  • They become symptomatic after arrival, but hospitals are already highly alert and prepared for quick isolation.

Majumda (08:22):

"In the US or Europe... that means isolation in high quality medical facilities. But that may not be possible in other countries in West Africa, which means that the chances of the outbreak transferring to a new country there are higher."

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5. Main Takeaways

• While Ebola is a deadly disease, the “90%” fatality figure is an outlier; average rates are much lower and vary by country.
• CFR does not measure how easily a disease spreads—Ebola’s transmissibility is low compared to common airborne viruses.
• Panic over global, intercontinental Ebola outbreaks is not substantiated by the science; focus should remain on containing outbreaks in West Africa.

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Notable Quotes & Memorable Moments

• “A CFR of 90% could be considered the upper limit... the cumulative average... is actually closer to about 60 to 65%.”
  — Maimouna Majumda, 02:15

• “When you have large ranges in CFR like you do with Ebola, it isn't really appropriate to give one extreme or the other.”
  — Majumda, 03:49

• “Measles is far more deadly... about 330 deaths every day, far more than are dying from Ebola.”
  — James Fletcher, 05:34

• “In theory, Ebola is a controllable disease, so we’re very unlikely to see a major outbreak in the UK, for example.”
  — Dr. Adam Kucharski, 06:44

• “The key cause for concern at the moment is dealing with the outbreak on the ground in West Africa, rather than the possibility that it will come to the US or Europe.”
  — James Fletcher, 08:22

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Segment Timestamps

• 00:13–01:36: Setting the scene—media panic and listener question
• 01:47–03:10: Fatality rate myths; what the “90%” number really means
• 03:10–03:49: Country-by-country CFR breakdown and causes of variation
• 03:49–04:47: Factors affecting fatality, recommendations for responsible statistics
• 04:53–05:47: Transmission risk and statistics compared to other diseases
• 05:47–06:44: Global concerns, flight bans, and public anxiety
• 06:44–08:22: Expert epidemiological context; improbability of global spread
• 08:22–08:47: Emphasis on West Africa as the key battleground

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Conclusion

The “Ebola kills 90%” statistic is misleading and is based on an extreme, not the typical, case. Most outbreaks have had much lower fatality rates, and the risk of intercontinental spread is extremely low compared to more contagious diseases. The episode calls for context, rationality, and focus where it matters: stopping transmission in affected regions, not fuelling unwarranted panic elsewhere.

Transcript

[BBC Announcer]

Thank you for downloading from the BBC. For details of our complete range of podcasts and our terms of use, go to bbcworldservice.com podcasts

[Ruth Alexander]

hello and welcome to More or Less on the BBC World Service. I'm Ruth Alexander, and if you've been listening to the news lately, you could be forgiven for feeling worried.

[Maimouna Majumda]

A big outbreak of the deadly Ebola

[James Fletcher]

virus in West Africa. The largest Ebola outbreak in history. Treatment or vaccine?

[Maimouna Majumda]

Ebola is probably the most contagious and most deadly virus in the world.

[Ruth Alexander]

The strain can kill up to 90% of its victims.

[James Fletcher]

Most of those who get it will die through uncontrollable bleeding.

[Ruth Alexander]

The outbreak of the lethal Ebola virus has spread in West Africa, affecting Guinea, Liberia, Sierra Leone and Nigeria. As we heard there, this is the deadliest outbreak of the disease to date, killing almost 1,000 people so far. And as a deadly virus with graphic effects, it seems the stuff of those dramatic Hollywood films about deadly viral pandemics. But before we panic, let's think, because More or Less listener Max Cousens has been in touch with a question.

[BBC Announcer]

A widely reported statistic is that Ebola kills up to 90% of those infected. I've been wondering what this statement actually means. Is it that 90% die in some areas and less than 90% in others? If so, to what extent? And why do mortality rates vary?

[Ruth Alexander]

Yes, we've heard this statistic over and over again in news reports, but what does it actually signify, more or less? James Fletcher has been finding out and he's here to tell us.

[James Fletcher]

Hi, Ruth. This figure of up to 90% comes from the World Health Organisation. It's a fairly simple measure called the case fatality rate. That's the number of people who die from an illness divided by the number of people who are diagnosed with that illness. Now, we asked Maimouna Majumda, she's a biostatistician and epidemiologist at MIT University in the United States, what the WHO mean when they talk about a fatality rate of up to 90%.

[Maimouna Majumda]

That 90% figure actually comes from one outbreak of Ebola, which took place in the Congo between 2002 and 2003. So it's the highest rate we've ever seen. We've also seen CFRs much lower than that in previous outbreaks, and I think that's something important to keep in mind. A CFR of 90% could be considered the upper limit of outbreaks caused by Zarebola virus. The cumulative average, considering all Ebola cases and deaths from 1976 to present is actually closer to about 60 to 65%. And the current outbreak thus far far has a CFR of about 54%, though it's subject to change as the outbreak wanes on.

[Ruth Alexander]

Maimouna Majumda there said the current fatality rate is 54%. And as Max, our listener was wondering, are all the countries with Ebola cases seeing that kind of rate?

[James Fletcher]

No. So at the moment, the fatality rate varies a lot between the western African countries that are affected. The worst affected country is guinea, which, which was the first where the Ebola showed up. That's got a fatality rate of around 73%, whereas in Liberia it's lower at 55%. In Sierra Leone it's 41%. And in the most recently affected country, Nigeria, it's much smaller at 11%, although they've only seen a handful of cases there. So it's not really possible to draw firm conclusions about how deadly the outbreak there is or could be.

[Ruth Alexander]

Those are big differences though.

[James Fletcher]

Yes. Maimouna Majumda explains what can cause those variations in the fatality rates.

[Maimouna Majumda]

The two biggest factors that are influencing case fatality rate are first, familiarity with the disease. This is the first time that we've seen Ebola in West Africa, so it caught everybody by surprise. And the second is availability of resources to contain, prevent and treat the people that are. When you have large ranges in CFR like you do with Ebola, it isn't really appropriate to give one extreme or the other. I think if we were to use CFR for Ebola, we really ought to give the cumulative average since the initial emergence of the disease in 1976. And that's significantly less than the 90% estimate that we hear a lot in the media and in news reports.

[James Fletcher]

And just a reminder that that all time figure for ebola is around 60 to 65%. So that shows that Ebola still kills the majority of people who contract it. And it is a nasty disease.

[Ruth Alexander]

But that brings us to another question, doesn't it? What are the chances of getting it in the first place?

[James Fletcher]

Yeah, that's one of the key things here because we've been talking so far about how deadly the disease is once you've got it. But this case fatality rate doesn't tell you whether it's easy to get the disease, how communicable it is. And it turns out Ebola is nowhere near as contag contagious as things such as flu or measles, for example. They both spread easily through the air, whereas Ebola is transmitted through contact with body fluids, which makes it much harder to get. So if we look at something like measles, the case fatality rate there in places where nutrition and healthcare are poor is around 10%, which is a lot lower than Ebola. But measles is far more deadly. According to the latest figures from the World Health organisation, more than 120,000 people died from it in 2012, and most of them were children under the age of five. So that's about 330 deaths every day, far more than are dying from Ebola.

[Ruth Alexander]

And talking about the risk of transmission, there's been a lot of concern about the Ebola virus spreading outside of West Africa, hasn't there? I mean, to the US or the uk, for instance. Airlines such as Emirates and British Airways have stopped or reduced flights into the region. And more controversially, American billionaire Donald Trump has been tweeting that infected medical staff shouldn't be allowed to return to the us and that, as he says, the US must immediately stop all flights from Ebola infected countries or the plague will start and spread inside our borders. I mean, we're back in the territory of thrillers here, aren't we?

[James Fletcher]

Yeah, at this point, I think we're pretty definitely left the world of rational calculation of risk. To put this in context, although the virus is still spreading in West Africa and more people are dying, it's considered pretty unlikely that there will be intercontinental outbreaks of the disease. Dr. Adam Kocharsky is an infectious disease epidemiologist at the London School of Hygiene and Tropical Medicine.

[Dr. Adam Kocharsky]

In theory, Ebola is a controllable disease, so we're very unlikely to see a major outbreak in the uk, for example. The reason being that Ebola, you don't become infectious until you're symptomatic. Contrast this with something like flu, where a lot of the infection occurs when people are walking about without symptoms and spreading the infection. Likewise, Ebola requires intense contact with body fluids. It's not airborne in the way that something like SARS or flu is.

[James Fletcher]

That isn't to say that there's no risk of people with Ebola arriving in other countries. It's just that it's very, very small and the chances of them starting an outbreak and spreading the disease are even smaller. We asked Maimouna Majumda from MIT to just spell out how difficult it would be for that to happen.

[Maimouna Majumda]

First and foremost, you would have to have a person that has Ebola get on a plane in West Africa en route to the United States. The likelihood of this is actually quite small because only about 1700 people have Ebola so far in this given outbreak. And West Africa is a big place. You would also need the person to not be symptomatic, because if they were symptomatic, they would be feeling so ill that they probably wouldn't be flying. So let's assume that does actually happen and they land in New York City, for instance. Now, by this time, if they're not showing symptoms yet, then there might be a potential for. For sustained transmission. What's more likely is that by the time that they arrive in the United States, they may not be feeling so well. If they're not and they turn themselves into a hospital, because the hospitals in New York City are very aware that this is a possibility, containment would occur right away.

[James Fletcher]

In the US or Europe, for example. That means isolation in high quality medical facilities. But that may not be possible in other countries in West Africa, which means that the chances of the outbreak transferring to a new country there are higher. So all of this suggests that the key cause for concern at the moment is dealing with the outbreak on the ground in West Africa, rather than the possibility that it will come to the US or Europe.

[Ruth Alexander]

James, thank you and thanks to Max for raising this question in the first place. That's all for this week's More or Less. Thank you for listening and please get in touch if you have any numbers you want us to look into. You can email us as Max did at more or lessbc.co.uk Previous editions of the programme are also available to download for [e-mail] More or less there are

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