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6 Charts That Will Help You Understand The Ebola Crisis

How bad is it really, how bad could it get – and how much should you worry?

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How many people have caught Ebola – and how many have died?

Tom Phillips/BuzzFeed / Via who.int

There has never been an Ebola outbreak on the scale of the current one; more than three times as many people are known to have died in this outbreak as died in all previous outbreaks put together.

Going by the raw numbers, it would appear that the "case fatality rate" – that is, the percentage of people who die after contracting the disease – is lower than in many previous outbreaks. At just under 50%, it would suggest that a bigger proportion of patients have survived Ebola than in all but three other outbreaks.

However, even that marginally hopeful sign may be optimistic. The chart above is based on current World Health Organisation figures, which the WHO openly says will underestimate the real figures by a significant amount due to the difficulty in tracking cases in regions where the health infrastructure has been overwhelmed. A study published in the New England Journal of Medicine found a case fatality rate of 70.8% up to 14 September when looking at only cases with "definitive recorded clinical outcomes".

The real figure for the number of cases and deaths in the epidemic to date could be twice as large as the figures shown above.

Tom Phillips/BuzzFeed / Via who.int

There has never been an Ebola outbreak on the scale of the current one; more than three times as many people are known to have died in this outbreak as died in all previous outbreaks put together.

Going by the raw numbers, it would appear that the "case fatality rate" – that is, the percentage of people who die after contracting the disease – is lower than in many previous outbreaks. At just under 50%, it would suggest that a bigger proportion of patients have survived Ebola than in all but three other outbreaks.

However, even that marginally hopeful sign may be optimistic. The chart above is based on current World Health Organisation figures, which the WHO openly says will underestimate the real figures by a significant amount due to the difficulty in tracking cases in regions where the health infrastructure has been overwhelmed. A study published in the New England Journal of Medicine found a case fatality rate of 70.8% up to 14 September when looking at only cases with "definitive recorded clinical outcomes".

The real figure for the number of cases and deaths in the epidemic to date could be twice as large as the figures shown above.

← Slide →
Tom Phillips/BuzzFeed / Via who.int

There has never been an Ebola outbreak on the scale of the current one; more than three times as many people are known to have died in this outbreak as died in all previous outbreaks put together.

Going by the raw numbers, it would appear that the "case fatality rate" – that is, the percentage of people who die after contracting the disease – is lower than in many previous outbreaks. At just under 50%, it would suggest that a bigger proportion of patients have survived Ebola than in all but three other outbreaks.

However, even that marginally hopeful sign may be optimistic. The chart above is based on current World Health Organisation figures, which the WHO openly says will underestimate the real figures by a significant amount due to the difficulty in tracking cases in regions where the health infrastructure has been overwhelmed. A study published in the New England Journal of Medicine found a case fatality rate of 70.8% up to 14 September when looking at only cases with "definitive recorded clinical outcomes".

The real figure for the number of cases and deaths in the epidemic to date could be twice as large as the figures shown above.

How bad could it get?

Tom Phillips/BuzzFeed / Via nejm.org and cdc.gov

The simple answer is: Nobody knows. The more complicated answer is: Lots of experts have made projections of how widely the epidemic could spread, but the number of uncertain factors involved (such as how well the medical infrastructure holds up, how many beds are available, how quickly new cases are reported and isolated, and how safely bodies are disposed of) mean that the range between the best and worst-case scenarios is vast.

Two sets of projections were made in late September. The WHO, in the same New England Journal of Medicine paper, projected that if the rate of increase didn't change, there could be 20,000 cases by early November. That may or may not be accurate: it's more than the current reported number of cases, but could accurately reflect the situation if (as the WHO suspects) the reporting infrastructure has collapsed in several of the worst affected countries.

At around the same time, the US Centers for Disease Control and Prevention (CDC) made a longer-term series of projections for the countries of Liberia and Sierra Leone that goes up until 20 January 2015. These took into account how successful the efforts to contain the disease could be. If the efforts were largely successful, the CDC predicted, the epidemic would be virtually over by that date. If the efforts were entirely unsuccessful or non-existent, then there could be as many as 1.4 million cases by then.

The point is not to say that one or the other projections may be right – they're not predictions as such, just models to guide policymakers towards the best decisions. Rather, they serve to point out the incredible amount of uncertainty when dealing with rapid outbreaks of infectious diseases.

How badly has Ebola hit healthcare workers?

Tom Phillips/BuzzFeed / Via apps.who.int

One reason Ebola is such a worrying disease is that, transmitted as it is by bodily fluids and close contact with the sick, it tends to hit healthcare workers especially hard. In the current outbreak, according to the most recent available figures for healthcare worker cases, almost 5% of those who have contracted Ebola have been healthcare workers. This is both cruel – killing those who tried to help others – and potentially very damaging to efforts to contain the epidemic.

However, it could be even worse: In the SARS outbreak of 2003, over 21% of those infected (1,706 out of 8,096) were healthcare workers.

Tom Phillips/BuzzFeed / Via apps.who.int

One reason Ebola is such a worrying disease is that, transmitted as it is by bodily fluids and close contact with the sick, it tends to hit healthcare workers especially hard. In the current outbreak, according to the most recent available figures for healthcare worker cases, almost 5% of those who have contracted Ebola have been healthcare workers. This is both cruel – killing those who tried to help others – and potentially very damaging to efforts to contain the epidemic.

However, it could be even worse: In the SARS outbreak of 2003, over 21% of those infected (1,706 out of 8,096) were healthcare workers.

← Slide →
Tom Phillips/BuzzFeed / Via apps.who.int

One reason Ebola is such a worrying disease is that, transmitted as it is by bodily fluids and close contact with the sick, it tends to hit healthcare workers especially hard. In the current outbreak, according to the most recent available figures for healthcare worker cases, almost 5% of those who have contracted Ebola have been healthcare workers. This is both cruel – killing those who tried to help others – and potentially very damaging to efforts to contain the epidemic.

However, it could be even worse: In the SARS outbreak of 2003, over 21% of those infected (1,706 out of 8,096) were healthcare workers.

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Is Ebola the biggest killer in Africa?

Tom Phillips/BuzzFeed / Via who.int

As critical as the situation in Guinea, Liberia and Sierra Leone is, Ebola is still not the biggest killer in the area – yet. In just those three countries alone, diseases such as malaria, HIV/AIDS, tuberculosis, and meningitis caused more deaths in 2012 (the most recent year for which we have figures) than Ebola is known to have caused in the outbreak to date. More deaths also result from babies dying at birth and malnutrition.

Obviously, this will change if the epidemic continues, or the current figures are revised upwards due to underreporting.

When you look at Africa as a whole, HIV is by far the biggest killer – and the effect of Ebola so far is dwarfed by many of the continent's biggest causes of death (plus many others not shown on the chart above, such as respiratory infections and diarrhoeal diseases). Crucially, unlike Ebola, several of these mass-scale killers are already preventable or curable.

Tom Phillips/BuzzFeed / Via who.int

As critical as the situation in Guinea, Liberia and Sierra Leone is, Ebola is still not the biggest killer in the area – yet. In just those three countries alone, diseases such as malaria, HIV/AIDS, tuberculosis, and meningitis caused more deaths in 2012 (the most recent year for which we have figures) than Ebola is known to have caused in the outbreak to date. More deaths also result from babies dying at birth and malnutrition.

Obviously, this will change if the epidemic continues, or the current figures are revised upwards due to underreporting.

When you look at Africa as a whole, HIV is by far the biggest killer – and the effect of Ebola so far is dwarfed by many of the continent's biggest causes of death (plus many others not shown on the chart above, such as respiratory infections and diarrhoeal diseases). Crucially, unlike Ebola, several of these mass-scale killers are already preventable or curable.

← Slide →
Tom Phillips/BuzzFeed / Via who.int

As critical as the situation in Guinea, Liberia and Sierra Leone is, Ebola is still not the biggest killer in the area – yet. In just those three countries alone, diseases such as malaria, HIV/AIDS, tuberculosis, and meningitis caused more deaths in 2012 (the most recent year for which we have figures) than Ebola is known to have caused in the outbreak to date. More deaths also result from babies dying at birth and malnutrition.

Obviously, this will change if the epidemic continues, or the current figures are revised upwards due to underreporting.

When you look at Africa as a whole, HIV is by far the biggest killer – and the effect of Ebola so far is dwarfed by many of the continent's biggest causes of death (plus many others not shown on the chart above, such as respiratory infections and diarrhoeal diseases). Crucially, unlike Ebola, several of these mass-scale killers are already preventable or curable.

Is Ebola as contagious as people say?

Tom Phillips/BuzzFeed/kanate/Thinkstock / Via docs.google.com

The simple answer is: No. As David Quammen puts it in his book Spillover: "Ebolaviruses have force but not reach... In the terms used by the scientists: It's not very contagious but it's highly infectious." Put simply, while you only need to be exposed to a tiny amount of an ebolavirus to become infected, not that many people actually get exposed.

How contagious a disease is can be measured by something called the Basic Reproduction Number, usually written as "R0", which simply means the average number of people that one person with the disease will infect (assuming they're in a susceptible, unvaccinated population.)

The current Ebola outbreak has an R0 that ranges between 1.7 (in Guinea) and 2.0 (in Sierra Leone), according to the same NEJM study referenced before. That's a lot less than many other major diseases, including HIV and measles (which is one of the most contagious diseases known.)

The basic reproduction number for any particular disease isn't a fixed value, of course; it depends to a large extent on the environment and society it's present in, and what steps health authorities can take to stop its spread – which is why the ranges for SARS, polio, and HIV given above are so wide. If medical efforts to identify and isolate Ebola sufferers before they can infect others pay off, the disease's R0 will decrease. And if a disease's R0 falls below the magic number of 1, then the infection will begin to die out.

Should the US be panicking over Ebola?

Tom Phillips/BuzzFeed / Via apps.who.int

Let's put it this way: There are places much worse off than America. Not only is it isolated by an ocean from the source of the outbreak, meaning only a handful of cases have appeared there so far, but it has medical infrastructure that is overwhelmingly better equipped to deal with cases that do arrive than the worst affected countries. To take just two measures of healthcare infrastructure quality, the US has the highest per-capita spending on health of any country in the world (even after you adjust for things being more expensive in the US), and it has almost 25 times as many physicians per person than even the best equipped country at the centre of the outbreak.

A major reason Ebola has spread so virulently through Guinea, Liberia, and Sierra Leone is that those countries' already-rickety medical systems have been overwhelmed. That is incredibly unlikely to happen in any wealthy Western country.

Tom Phillips/BuzzFeed / Via apps.who.int

Let's put it this way: There are places much worse off than America. Not only is it isolated by an ocean from the source of the outbreak, meaning only a handful of cases have appeared there so far, but it has medical infrastructure that is overwhelmingly better equipped to deal with cases that do arrive than the worst affected countries. To take just two measures of healthcare infrastructure quality, the US has the highest per-capita spending on health of any country in the world (even after you adjust for things being more expensive in the US), and it has almost 25 times as many physicians per person than even the best equipped country at the centre of the outbreak.

A major reason Ebola has spread so virulently through Guinea, Liberia, and Sierra Leone is that those countries' already-rickety medical systems have been overwhelmed. That is incredibly unlikely to happen in any wealthy Western country.

← Slide →
Tom Phillips/BuzzFeed / Via apps.who.int

Let's put it this way: There are places much worse off than America. Not only is it isolated by an ocean from the source of the outbreak, meaning only a handful of cases have appeared there so far, but it has medical infrastructure that is overwhelmingly better equipped to deal with cases that do arrive than the worst affected countries. To take just two measures of healthcare infrastructure quality, the US has the highest per-capita spending on health of any country in the world (even after you adjust for things being more expensive in the US), and it has almost 25 times as many physicians per person than even the best equipped country at the centre of the outbreak.

A major reason Ebola has spread so virulently through Guinea, Liberia, and Sierra Leone is that those countries' already-rickety medical systems have been overwhelmed. That is incredibly unlikely to happen in any wealthy Western country.