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| Ebola outbreak: How many people have died? | Ebola outbreak: How many people have died? |
| (about 1 hour later) | |
| How many people have died from Ebola in West Africa? | How many people have died from Ebola in West Africa? |
| It sounds an easy question, but the answer is certainly not. | It sounds an easy question, but the answer is certainly not. |
| The most recent official figure from the World Health Organization puts the number of deaths at 4,447. | The most recent official figure from the World Health Organization puts the number of deaths at 4,447. |
| But 12,000 could be a better estimate. Getting to this figure highlights a number of issues with the Ebola data. | But 12,000 could be a better estimate. Getting to this figure highlights a number of issues with the Ebola data. |
| How many cases? | How many cases? |
| First of all there is a fair bit of uncertainty about how many people have Ebola. | First of all there is a fair bit of uncertainty about how many people have Ebola. |
| The ones we know about stand at 8,914 - this is made up of confirmed, suspected and probable cases. | The ones we know about stand at 8,914 - this is made up of confirmed, suspected and probable cases. |
| However, Liberia, Sierra Leone and Guinea have some of the worst-funded healthcare systems in the world. | However, Liberia, Sierra Leone and Guinea have some of the worst-funded healthcare systems in the world. |
| We know people are contracting the disease, and dying from it, without being noticed. | We know people are contracting the disease, and dying from it, without being noticed. |
| Based on small trials, agencies including the WHO and the US Centers for Disease Control are taking an "educated guess" that the figure is around twice that. | Based on small trials, agencies including the WHO and the US Centers for Disease Control are taking an "educated guess" that the figure is around twice that. |
| The widely reported estimate of 10,000 cases per week by December uses this doubling to account for under-reporting. | The widely reported estimate of 10,000 cases per week by December uses this doubling to account for under-reporting. |
| "We get that because 5,000 is the midpoint of our modelling scenarios and if we allow for under-reporting [by a factor of two] then that's 10,000," said Dr Christopher Dye, the director of strategy in the office of the director general at the WHO. | "We get that because 5,000 is the midpoint of our modelling scenarios and if we allow for under-reporting [by a factor of two] then that's 10,000," said Dr Christopher Dye, the director of strategy in the office of the director general at the WHO. |
| Use the same principle and the number of cases now could be around 18,000. | Use the same principle and the number of cases now could be around 18,000. |
| What is the death rate? | What is the death rate? |
| Looking at the official figures again - 8,914 cases and 4,447 deaths - you might think that roughly half of patients die. | Looking at the official figures again - 8,914 cases and 4,447 deaths - you might think that roughly half of patients die. |
| "This is wrong," Dr Dye told me. | "This is wrong," Dr Dye told me. |
| The data is, quite frankly, a bit of a mess. | The data is, quite frankly, a bit of a mess. |
| Take the WHO Ebola response roadmap update on 10 October. It has more confirmed deaths in Liberia from Ebola (1,072) than actual cases (943). | Take the WHO Ebola response roadmap update on 10 October. It has more confirmed deaths in Liberia from Ebola (1,072) than actual cases (943). |
| This confusing set of figures comes about by collecting data on cases and deaths separately. | This confusing set of figures comes about by collecting data on cases and deaths separately. |
| Also, comparing current cases and current deaths does not take account of people living with the disease for some time before either dying or recovering. | Also, comparing current cases and current deaths does not take account of people living with the disease for some time before either dying or recovering. |
| What you need is quality data and the best comes from a report in the New England Journal of Medicine. | What you need is quality data and the best comes from a report in the New England Journal of Medicine. |
| A team, including scientists at Imperial College London, looked at a sub-set of patients with full medical records from diagnosis through to either recovery or death. | A team, including scientists at Imperial College London, looked at a sub-set of patients with full medical records from diagnosis through to either recovery or death. |
| Dr Dye told the BBC: "On the basis of this analysis, our best estimate is a 60-70% case fatality and it's sensible to use a range as there are variations from one place to another." | Dr Dye told the BBC: "On the basis of this analysis, our best estimate is a 60-70% case fatality and it's sensible to use a range as there are variations from one place to another." |
| Use the 70% figure on the 18,000 estimated cases and it seems around 12,000 are either dead or dying. | Use the 70% figure on the 18,000 estimated cases and it seems around 12,000 are either dead or dying. |
| Clearly that is not a definitive figure, but getting there shows how messy some of the data are. | Clearly that is not a definitive figure, but getting there shows how messy some of the data are. |
| And this is the same basic data being used to reach forecasts of 1.4 million cases by January or 10,000 new cases a week by December. |