How many people have REALLY caught the coronavirus?

How many people in London have REALLY had coronavirus? Antibody surveillance studies suggest up to 2.6MILLION residents could have already caught it as Professor Chris Whitty admits he thinks at least 10% of the capital has been infected

  • Early antibody tests suggest up to a third of population infected in some places
  • Sweden says it expects at least 25 per cent to have been infected by May
  • Surveys in Europe place past infection rate at between 3 and 14 per cent 
  • Here’s how to help people impacted by Covid-19

More than 2.6million people in London may have already caught the coronavirus and recovered from it, data suggests.

Early results from antibody surveys – which reveal how many people have had the illness already – suggest the true death rate for COVID-19 may be anywhere between 0.1 and 0.6 per cent. 

The UK’s current death rate, of 14 per cent, is far higher than the reality because the Government abandoned plans to test members of the public at the start of the outbreak, opting only to screen hospital patients and staff.

As the real, considerably lower, death rate emerges the number of people estimated to have been infected will soar. A rate of 0.1 per cent, for example, means that for every one person who dies there are 999 people who survived the illness.

Applied to the 5,059 deaths estimated to have happened in NHS hospitals and care homes in London already, this suggests 5,059,000 people have already been infected with the coronavirus.

Random testing in New York suggests the death rate there is more like 0.57 per cent which, applied to London, would mean 887,543 people had been infected.

Similar projects and preliminary fatality rates in Finland, Germany and Sweden would suggest the number of people infected in the English capital is between 1.2m and 2.6m. 

These studies show that surveys in some communities found up to a third of people have been infected with the virus and recovered.

More than 2.7million people around the world have now been diagnosed with COVID-19 but the true number of those who have caught it remains a mystery.

Sweden says a quarter of its population will have caught the coronavirus already by the end of this month, putting the country on its way to herd immunity.

And one in five people in New York City, one of the worst-hit places in the world, returned positive results in tests to see if they had already recovered from COVID-19.

These tests, called antibody tests, check for signs in a patient’s blood that their immune system has learned how to fight off the disease after being exposed to it.

Surveys are ongoing around the world and early results show that in some communities almost one in three people have already been infected and recovered.

These figures can give an insight into the real fatality rate among people infected by the coronavirus, by comparing the number of deaths to the real number of people who caught the illness, not just those who were officially tested or hospitalised.

Antibody surveys in New York City, Stockholm, Helsinki and Gangelt in Germany may give some insight into how deadly the virus really is.

Early in the UK’s outbreak, Government scientists suggested that a death rate of 0.1 per cent – one in a thousand – was likely to be reliable but to eventually turn out too high.

A study in New York state found 14 per cent of its residents had signs of past infection. Compared to the 15,470 deaths officially recorded there, this puts the state’s death rate at 0.57 per cent.

Similar studies presented possible death rates in Stockholm, Sweden (0.4 per cent); Helsinki, Finland (0.19 per cent) and Gangelt, Germany (0.37 per cent).

Applying these figures to the number of deaths that have happened in London already could give an idea of how many people have been infected in the city.

By April 23, NHS England reported 4,300 COVID-19 deaths in London hospitals, and data from the Office for National Statistics suggest hospital fatalities make up 85 per cent of the total – putting London’s true number of victims at 5,059 by that date.

Some sources put the number of deaths happening outside of hospitals considerably higher – it is around a third in care homes in Scotland and Northern Ireland – so 5,059 is a conservative estimate based on existing data for England. 

Extrapolating from 5,059 using the death rates of cities where antibody testing has been carried out puts London’s true number of cases at somewhere between 1.26million and 5.05million like so:

  • 0.1% death rate (Early Government estimate) – 5,059,000 cases in London
  • 0.19% death rate (Helsinki, Finland) – 2,662,631 cases in London
  • 0.37% death rate (Gangelt, Germany) – 1,367,297 cases in London
  • 0.4% death rate (Stockholm, Sweden) – 1,264,750 cases in London
  • 0.57% death rate (New York state) – 887,543 cases in London

Understanding the true numbers of people who have had the virus and not become seriously ill is the only way scientists will be able to work out the virus’s true death rate.

While some countries in Europe are recording death rates of more than 10 per cent among hospital patients, in wider society the likelihood of death appears consistently below one in 100 patients (one per cent).

Early antibody survey results show that more than 30 per cent of people have been infected in Chelsea, Massachusetts, 14 per cent in the German district of Heinsberg, around three per cent in Oise, northern France, and 11 per cent in Stockholm. 

The World Health Organization said the antibody surveys it has seen suggest the world is nowhere near developing herd immunity against the coronavirus.

Dr Tedros Adhanom Ghebreyesus, director-general of the WHO, predicted that between two and three per cent of the global population has had COVID-19. 

If true, this suggests 190million people worldwide have caught the virus in the four months since it emerged.

For herd immunity to develop, a community’s rate is likely to need to be higher than 66 per cent, the UK’s chief scientist, Sir Patrick Vallance, has suggested. 

Herd immunity protects people from a disease by virtue of so many people being immune to it that it cannot spread through the population.

WHAT CAN ANTIBODY TESTS SHOW US ABOUT THE VIRUS’S TRUE DEATH RATE? 

The true death rate of COVID-19 is unknown because of the way the virus is being tracked around the world.

Most countries are only diagnosing people in hospitals or those with bad symptoms, meaning the number of patients they record is significantly lower than the reality.

Many patients, scientists say, develop only mild illnesses or don’t get any symptoms at all, meaning they are never tested and never counted.

As a result, the ratio of people dying to people diagnosed is artificially high.

Using antibody tests to understand the true – much larger – numbers of people who have caught the virus, and then working out what proportion of them have died, will provide more accurate death rates in the future.

Early antibody surveys have already started to shine light in this area: 

LOS ANGELES, CALIFORNIA 

Blood samples in Los Angeles suggest the coronavirus death rate could be around 0.18 per cent.

A study of 846 people found roughly 4.1 per cent of the county’s 3.9million population has antibodies to the virus.

It means that roughly 330,000 people have already caught the illness and built up some immunity to it.

There were officially 600 COVID-19 deaths when the research was conducted on April 20.

This suggests that around 0.18 per cent of patients fall victim to the disease. 

CHELSEA, MASSACHUSETTS 

US researchers in Boston found almost a third (31.5 per cent) of residents in the suburb of Chelsea had antibodies for the virus.

They collected blood samples from 200 random volunteers and said roughly 63 people had probably caught the illness.

The city of Chelsea is home to around 40,160 people. If the results were to be extrapolated to the whole city, it suggests 12,650 may have actually been infected.

When the study was published on April 17, Chelsea had suffered 39 deaths to coronavirus.

The finding suggests the true death rate it around 0.31 per cent.

GANGELT, GERMANY

Scientists studying Gangelt, dubbed the ‘German Wuhan’, found as many as 15 per cent of people may have already been infected with the virus.

Data shows around 12,500 people live in the municipality, which sits in the North-Western state of North Rhine-Westphalia.

If the results were to be extrapolated to the whole of Gangelt, it would mean that around 1,900 people have already caught the deadly virus.

It is not clear exactly how many people had died in Gangelt by the time that the University of Bonn study of 1,000 people was published.

But the team – whose work was not scrutinised and published in a journal – estimated the true death rate was in the region of 0.37 per cent.  

THE NETHERLANDS

An antibody surveillance scheme in the Netherlands suggested the death rate for COVID-19 could actually be in the region of 0.63 per cent.

Dutch researchers found antibodies in three per cent of blood donors, after analysing samples from around 7,000 people aged between 18 and 69.

The head of the Netherlands’ National Institute for Health told MPs it meant that ‘several hundred thousand people’ may have already been infected.

Around 17.28million people live in the Netherlands. Three per cent of the country’s population would equate to approximately 518,400. 

When results were published on April 16, official figures showed that 3,315 people had died after testing positive for COVID-19 in the Netherlands.

HELSINKI, FINLAND

Finnish researchers analysed around 150 blood samples by mid-April and found 3.4 per cent had antibodies for the coronavirus.

The samples were all taken from the region of Uusima, which is home to approximately 1.7million people – most of whom live in the capital of Helsinki.

At the time, only 2,000 cases had been confirmed by laboratory tests. But 3.4 per of the region’s population would equate to around 57,800.

Only 110 deaths have been registered in Uusima to-date – suggesting that the true fatality rate is closer to the 0.19 per cent mark.  

The study was released on April 15 – but the region’s death toll has barely changed in the past week. It was not published in a journal. 

Of early surveys to work out the levels of immunity in the population, the city of Chelsea in Massachusetts, USA, has shown the largest scale of infection.

A total 31.5 per cent of people there tested positive in a small sample of 200 random passers-by, carried out by scientists at the Massachusetts General Hospital.

Meanwhile, rapid testing in New York city and state revealed that some 21 per cent of people in the city had antibodies against the virus, and 14 per cent statewide.

Antibodies are substances which people’s immune systems develop to remember how to fight off the virus the next time they come into contact with it. They are only producible through real-world infection or a vaccine – and there is no vaccine yet for the virus.

The figures from New York suggest millions of people among its population of 19million have caught the virus and recovered without being recorded.

The district of Heinsberg in Germany, and a town inside it – Gangelt – showed similar rates of immunity in blood bank screening in March.

Fourteen per cent of people there tested positive for antibodies in a sample of around 1,500 people.

In Sweden’s capital, Stockholm, where the government has staunchly refused to put the country into lockdown, screening in blood donation centres showed that at least 11 per cent of residents have been exposed to the virus.

Swedish officials appear to be pursuing plans to develop herd immunity – which were met with outrage when suggested in Britain – and say that they expect between a quarter and a third of the nation will already have been infected by the end of this month.

One academic at Stockholm University, Tom Britton, predicts that half of the people in the capital city will have caught the virus by May 1. 

Despite business there continuing as usual with only advice to people to try social distancing, the country has recorded few deaths, with just 2,000 recorded victims.

Exposure rates are considerably lower in other areas.

In Oise, a small region in the north of France, blood bank screening found that three per cent of the population had evidence of past COVID-19 infection.

The same study found that, in a small school community there, this rate soared to 26 per cent, showing there is scope for wide variations even within regions.

Tests in California showed similarly low levels of infection. Testing from Santa Clara County pointed to approximately 2.8 per cent of people having been infected, while Los Angeles County testing put the figure at 4.1 per cent.

These were pulled from studies done on 3,300 people and 846 people, respectively.

Finland’s capital region, Uusimaa, which is centred around Helsinki, showed around 3.4 per cent of people had evidence of past infection in a study of 442.

A World Health Organization scientist, Dr Maria Van Kerkhove, said the number of people testing positive for antibodies was lower than experts had hoped for.

Dr Kerkhove said: ‘Initially, we see a lower proportion of people with antibodies than we were expecting. A lower number of people are infected,’ The Guardian reported. 

Dr Joe Grove, a virologist at University College London, told MailOnline: ‘Antibody testing is important because the better we understand the virus, the better we can respond to it.

‘The true death rate allows public health experts and epidemiologist to asses what the effects of another epidemic would be.

‘A lot of our current policy has been determined by the predictions of computer simulations. But those models are only as good as the data you put into them. 

‘So there would’ve been estimates of death rates and infections, but as we get firmer numbers we can run more accurate simulations and predict with more confidence what might happen in future. 

‘This is critical for working out if given epidemic will overwhelm the healthcare system again.’ 

Current antibody surveys are limited by the quality of the tests being used, the small numbers of people recruited in the studies and a poor understanding of immunity.

Because the virus has never been seen before, health authorities around the world are still scrambling to find reliable test to spot the antibodies created to fight it.

In some cases, patients don’t seem to produce detectable levels of antibodies at all, which has led scientists to fear that people do not become immune to COVID-19 after recovering from it. If that was the case, the virus could become unstoppable.

The tests that are being used vary from country to country.

Some being used in Spain have an accuracy of just 80 per cent, while some made in Belgium claim to be 100 per cent accurate.

Forced social distancing has not been put in place in Sweden and business has carried on as normal. As a result, officials predict around a quarter of the population will have caught the virus – and the vast majority recovered from it – by the end of the month

The one commercial test approved by the Food & Drug Administration in the US is around 95 per cent accurate.

WHY EARLY ANTIBODY SURVEYS SHOULD BE TAKEN WITH A PINCH OF SALT 

Current antibody surveys are limited by the quality of the tests being used, the small numbers of people recruited in the studies and a poor understanding of immunity.

Because the virus has never been seen before, health authorities around the world are still scrambling to find reliable test to spot the antibodies created to fight it.

In some cases, patients don’t seem to produce detectable levels of antibodies at all, which has led scientists to fear that people do not become immune to COVID-19 after recovering from it, as they would with measles or strains of cold and flu viruses.

The tests that are being used vary from country to country.

Some being used in Spain have an accuracy of just 80 per cent, while some made in Belgium claim to be 100 per cent accurate.

The one commercial test approved by the Food & Drug Administration in the US is around 95 per cent accurate.

Low accuracy in tests means false positives show antibodies where there are none, or miss them in false negatives from people who have been ill. 

And the studies that have been done so far are very small by normal scientific standards – they would not be considered acceptable in drug trials or studies into the causes of diseases.

The largest of those listed above was on 7,000 people in the Netherlands – 0.04 per cent of the country’s population – and the smallest was done on just 200 people in Chelsea, Massachusetts.

Although this may still give useful insight, such small studies are at a very high risk of being confounded – thrown off course – by random chance factors or errors.

For example, if a small study like the one in Chelsea, MA, happened to have been done in a place with a COVID-19 outbreak much more ferocious than the state as a whole – because of a high population of old people, for example – its results would not be representative of other areas, even if they were nearby. 

Low accuracy in tests means false positives show antibodies where there are none, or miss them in false negatives from people who have been ill.  

At the moment, the average risk of someone dying if they catch the coronavirus is relatively unknown because of the way people are tested. 

Most countries are only diagnosing people in hospitals or those with bad symptoms, meaning the number of patients they record is significantly lower than the reality.

Many patients, scientists say, develop only mild illnesses or don’t get any symptoms at all, meaning they are never tested and never counted.

As a result, the ratio of people dying to people diagnosed is artificially high.

Using antibody tests to understand the true – much larger – numbers of people who have caught the virus, and then working out what proportion of them have died, will provide more accurate death rates in the future.

The early antibody surveys mentioned above can go some way to shining light on the real likelihood of dying if you catch the coronavirus.

For example, in France, official figures put the country’s death rate at a staggeringly high 13.58 per cent – one in every seven people. 

However, antibody surveys from blood banks in the town of Oise, found that three per cent of the general public had been exposed to the virus, a figure that chimes with the WHO’s global estimate.

If this is extrapolated to the wider Hauts-de-France region, home to six million people, that suggests 180,000 people were infected by the time the samples were taken in the last week of March.

At that time, just 109 people had died in the region. 109 deaths from 180,000 people puts the region’s death rate at 0.06 per cent.

New York could similarly see its fatality rate come crashing down if the wider estimates of infection turn out to be accurate.

The state’s governor, Andrew Cuomo, said an infection rate of 13.9 per cent, suggested by the early antibody survey would suggest 2.7million people had caught the virus.

The state had recorded 15,470 deaths by Thursday, April 23, which would put its true fatality rate at 0.57 per cent – it currently appears around 10 times higher than that.

Mr Cuomo said in a news briefing: ‘If the infection rate is 13.9 percent, then it changes the theories of what the death rate is if you get infected.’ 

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