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Coronavirus death rate: What are the chances of dying? Coronavirus death rate: What are the chances of dying?
(21 days later)
Researchers currently think that between five and 40 coronavirus cases in 1,000 will result in death, with a best guess of nine in 1,000 or about 1%. The UK government's scientific advisers believe that the chances of dying from a coronavirus infection are between 0.5% and 1%.
On Tuesday, the World Health Organization's Director General, Tedros Adhanom Ghebreyesus, said that "globally, about 3.4% of reported Covid-19 cases have died". This is lower than the rate of death among confirmed cases - which is 4% globally in WHO figures and 5% in the UK as of March 23 - because not all infections are confirmed by testing.
Scientists' estimate of the death rate is lower because not all cases are reported. Each country has its own way of deciding who gets tested, so comparing case numbers or apparent death rates across countries can also be misleading.
On Sunday, Health Secretary Matt Hancock said the UK government's "very best assessment" was that the mortality rate was "2% or, likely, lower". Death rates also depend on a range of factors like your age and general health, and the care you can access.
But it depends on a range of factors: your age, sex and general health and the health system you are in. What are the risks for people like me?
How hard is it to work out the death rate? The elderly and the unwell are more likely to die, if they contract coronavirus.
It is PhD-level hard. Even counting cases is tricky. Current estimates from Imperial College London are that the death rate is almost 10 times higher than average for those over 80, and much lower for those under 40.
Most cases of most viruses will go uncounted because people tend not to visit the doctor with mild symptoms. The UK government's chief medical advisor, Professor Chris Whitty, says even though the rates are higher for older people, "the great majority of older people will have a mild or moderate disease".
The different death rates we are seeing reported around the world are unlikely to be due to different versions of the virus. He also warns that we should not think it's a trivial infection for younger people, pointing out that there are some young people who have ended up in intensive care.
It's not just age that determines the risk of infections.
In the first big analysis of more than 44,000 cases from China, deaths were at least five times more common among confirmed cases with diabetes, high blood pressure or heart or breathing problems.
All of these factors interact with each other and we don't yet have a complete picture of the risk for every type of person in every location.
And even though patterns in the death rates among confirmed cases can tell us who is most at risk, they can't tell us about the precise risk in any single group.
The death rate in confirmed cases is not the overall death rate
Most cases of most viruses go uncounted because people tend not to visit the doctor with mild symptoms.
On 17 March, the chief scientific adviser for the UK, Sir Patrick Vallance, estimated there were about 55,000 cases in the UK, when the confirmed case count was just under 2,000.
Dividing deaths by 2,000 will give you a much higher death rate than dividing by 55,000.
That's one of the biggest reasons why the death rates among confirmed cases are a bad estimate of the true death rates: overestimating the severity by missing cases.
But you can also get it wrong in the other direction: underestimating the death rate by not taking into account those people currently infected who may eventually die.
Why do death rates differ between countries?
According to research by Imperial College, it's because different countries are better or worse at spotting the milder, harder to count cases.According to research by Imperial College, it's because different countries are better or worse at spotting the milder, harder to count cases.
So under-reporting cases makes it easy to overestimate the death rate. But you can also get it wrong in the other direction. Countries use different tests for the virus, have different testing capacity and different rules for who gets tested. All of these factors change over time.
It takes time before an infection results in recovery or death. The UK government plans to increase testing to 10,000 a day initially, with a goal of reaching 25,000 a day within four weeks. It currently restricts testing mainly to people in hospitals.
If you include all cases that haven't yet had a chance to run their course, you will underestimate the death rate because you are missing the cases that will end in death later. Germany has a daily testing capacity of more than 20,000 cases and has been testing people with mild symptoms.
So their counts of confirmed infections could capture different sections of the pyramid of cases shown above.
The death rate among confirmed cases in Germany (less than half a per cent) is among the lowest in Europe, but is expected to rise as the mix of patients getting tested changes.
Your prognosis also depends on the treatment that's available and whether the health service can deliver it.
In turn, that depends on the stage of the epidemic.
If a healthcare system gets swamped with cases and intensive care units can't treat people who need ventilation, then the death rate would go up.
How do scientists work out the true death rate?
Scientists combine individual pieces of evidence about each of these questions to build a picture of the death rate.Scientists combine individual pieces of evidence about each of these questions to build a picture of the death rate.
For example, they estimate the proportion of cases with mild symptoms from small, defined groups of people who are monitored very tightly, like people on repatriated flights. For example, they estimate the proportion of cases with mild symptoms from small, defined groups of people who are monitored very tightly, like those on repatriated flights.
But slightly different answers from those pieces of evidence will add up to big changes in the overall picture. But slightly different answers from these targeted pieces of evidence will add up to big changes in the overall picture.
If you just use data from Hubei, where the death rate has been much higher than elsewhere in China, then the overall death rate will look much worse. And the evidence will change over time.
So scientists give a range as well as a best current estimate. Paul Hunter, professor of medicine at the University of East Anglia, points out that death rates could go down as well as up.
But even that doesn't tell the full story because there is no single death rate. "With Ebola, they came down over time as people got better at treating the disease" but they can go up too: "If a healthcare system is overrun, then we see death rates rising".
What's the risk for people like me? So scientists give a an upper and a lower figure, as well as a best current estimate.
Even though the death rates among confirmed cases don't tell us about the precise risk in any single group, their patterns can tell us about who is most at risk.
Some types of people are more likely to die if they contract coronavirus: the elderly, the unwell and, maybe, men.
In the first big analysis of more than 44,000 cases from China, the death rate was ten times higher in the very elderly compared to the middle-aged.
The death rates were lowest for the under 30s - there were eight deaths in 4,500 cases.
And deaths were at least five times more common among people with diabetes, high blood pressure or heart or breathing problems.
There was even a slightly higher number of deaths among men compared to women.
All of these factors interact with each other and we don't yet have a complete picture of the risk for every type of person in every location.
What's the risk for people where I live?
A group of 80-year-old men in China could have very different risks to men of the same age in Europe or Africa.
Your prognosis also depends on the treatment you get.
In turn, that depends on what is available and the stage of the epidemic.
If the epidemic takes off, then healthcare systems could get swamped with cases - there are only so many intensive care units or ventilators available in any given area.
Is it more dangerous than flu?
We can't compare mortality rates because many people with mild flu symptoms choose never to visit a doctor.
So we don't know how many cases there are of flu, or any new virus every year.
But flu continues to kill people in the UK, as it does every winter.
As the data evolves, scientists will develop a clearer picture of who would be most at risk should a coronavirus outbreak arrive in the UK.
The basic advice from the WHO is that you can protect yourself from all respiratory viruses by washing your hands, avoiding people who are coughing and sneezing and trying not to touch your eyes, nose and mouth.
Have you been affected by the coronavirus? Or do you have any information to share? Get in touch by emailing haveyoursay@bbc.co.uk.Have you been affected by the coronavirus? Or do you have any information to share? Get in touch by emailing haveyoursay@bbc.co.uk.
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