Rate of Covid-19 infection in England dropped in May BEFORE lockdown restrictions were lifted
Coronavirus R rate in England was LOWER than officials thought in May as huge government-funded study estimates average of 0.57 for the month after SAGE claimed it was between 0.7 and 1
- More than 120,000 volunteers were tested across England in the month of May
- Every infected person was passing the virus on to 0.57 people during May
- It’s lower than what was estimated by the Government at the time
By Vanessa Chalmers Health Reporter For Mailonline and Sam Blanchard Senior Health Reporter For Mailonline
Published: 01:01 EDT, 15 July 2020 | Updated: 06:16 EDT, 15 July 2020
The reproduction rate of the coronavirus in England was significantly lower in May than Government scientists thought it was, a major study claimed today.
Covid-19 was spreading at an R rate of 0.57, on average, in the weeks before lockdown was lifted, according to scientists from Imperial College London.
Their research, which swab tested a massive 120,000 people across the country regardless of whether they felt ill, casts doubts on estimates by the scientific advisory group SAGE, which said in May that the R was between 0.7 and 1.0
The Imperial scientists found just 159 positive cases out of 120,610 people and they estimate the prevalence of the disease was halving every nine days.
Lockdown worked, researchers and politicians have deduced from the research, with one of those leading the study calling it ‘very effective at reducing the prevalence of the virus’.
Worryingly, the study estimated that 69 per cent of people who tested positive did not have any symptoms at all in the seven days leading up to their test.
And it found that coughing and a fever – two of just three symptoms officially recognised by UK officials – were not significant indicators that someone had the disease.
Currently people in Britain are only eligible for a test if they have a cough, fever or lose their sense of taste or smell.
But the Imperial research found that other more vague symptoms, like diarrhoea, vomiting, tiredness and chills were strongly linked to the virus. Lost smell or taste remained the strongest indicator, however.
The study swabbed 120,610 people over the age of five from a ‘a nationally representative sample of the population’. Some 159 were positive meaning 0.13 per cent of the population were infected in May. The variances over England are pictured
Trends in swab positivity: The black points show daily observed prevalence by day of swab
Professor Steven Riley, an infectious disease expert at Imperial College London who helped lead the study, said the paper adds to ‘very strong trends’ showing the rate of transmission fell dramatically during England’s lockdown.
‘We find pretty reliable evidence that it was declining,’ he said this morning, ‘and the rate it was declining was fairly substantial even at the end of the period [May].’
Professor Riley added: ‘The relatively low R value even towards the end of May suggests the lockdown was effective in the community.’
Asked about the fact that coughing was a weaker link to the virus than other symptoms like diarrhoea or vomiting, the researcher said those were likely more common in people with milder illness.
‘[Coughing and fever] are the reason that people become clinical cases so it’s not surprising to me that they are less common,’ Professor Riley said.
His colleague and the director of the study, Imperial College epidemiologist Professor Paul Elliott, added: ‘We highlighted the symptoms that were most significant.
‘Persistent cough was still reported – it’s not like it wasn’t there – it just wasn’t as significant as others.
‘All of these symptoms have been previously reported and clearly some of these, like diarrhoea, are non-specific.’
Health Secretary Matt Hancock said the study, which was repeated in June on an even larger section of the population, is crucial to the country’s ongoing battle with coronavirus.
‘This ambitious testing programme will help us better understand the spread of the virus to date, predict how it may spread in the future and inform our response to the pandemic,’ Mr Hancock said.
‘It shows the impact our national lockdown efforts have had and demonstrates that we have taken the right actions at the right time.’
Although he noted the country had taken ‘great strides towards beating this virus’, we ‘mustn’t take our foot off the pedal’.
The study swabbed 120,610 people over the age of five from a ‘a nationally representative sample of the population’.
Only 159 were positive meaning 0.13 per cent of the population were infected in May.
WHAT IS THE R RATE?
Every infectious disease is given a reproduction number, which is known as R0 – pronounced ‘R nought’.
It is a value that represents how many people one sick person will, on average, infect if nobody has any immunity to the disease.
When an outbreak has been running for a while and more people have had the illness and taken steps to avoid it, the reproduction number is referred to as Re or just R.
This means it is based more on the circumstances in which the virus is spreading than on its natural properties. The R takes into account human actions – such as lockdown in the case of Covid-19 – whereas R0 does not.
WHAT IS THE R0 FOR COVID-19?
The R0 value for SARS-CoV-2, the virus that causes COVID-19, was estimated by the Imperial College COVID-19 Response Team to be 2.4 in the UK before lockdown started.
But some experts analysing outbreaks across the world have estimated it could be closer to the 6.6 mark.
Estimates of the R0 vary because the true size of the pandemic remains a mystery, and how fast the virus spreads depends on the environment.
It will spread faster in a densely-populated city where people travel on the subway than it will in a rural community where people drive everywhere.
HOW DOES IT COMPARE TO OTHER VIRUSES?
It is thought to be at least three times more contagious than the coronavirus that causes MERS (0.3 – 0.8).
Measles is one of the most contagious infectious diseases, and has an R0 value of 12 to 18 if left uncontrolled. Widespread vaccination keeps it suppressed in most developed countries.
Chickenpox’s R0 is estimated to be between 10 and 12, while seasonal flu has a value of around 1.5.
WHY IS IT IMPORTANT TO HAVE A LOW R0?
The higher the R0 value, the harder it is for health officials control the spread of the disease.
A number lower than one means the outbreak will run out of steam and be forced to an end.
This is because the infectious disease will quickly run out of new victims to strike.
HOW DOES A LOCKDOWN BRING DOWN THE R0?
The UK’s draconian lockdown, imposed on March 23 has slowed Britain’s coronavirus crisis, studies show.
Scientists at the London School of Hygiene and Tropical Medicine last month analysed the virus in the UK.
They estimated each infected patient may now only be passing COVID-19 on to 0.62 others, down from 2.6.
The team said the virus was struggling to spread because people were having less contact with others.
They used a survey of 1,300 people who were asked to list what human contact they had in the past 24 hours.
This was compared to a similar survey done in 2005 to give an idea of how it had changed because of lockdown.
It suggests that up to 115,000 people in England may have been infected with Covid-19 on any given day in May.
Young adults aged between 18 and 24, people of Asian ethnicity, and care home workers were most likely to test positive for Covid-19.
Prevalence of the infection was highest in London, up to 0.2 per cent of the population, followed by the West Midlands. It was lowest in the South West at 0.06 per cent, evident by the regions drastically lower cases and deaths.
Imperial’s research showed infections decreased over May, with the infection rate halving every eight to nine days.
They gave an overall reproduction number of 0.57 — with a possible range of between 0.45 and 0.72 — but did not reveal how this changed over the month.
The estimates are different to those made by the Office for National Statistics, which swabbed a lower number of 14,599 people in 7,054 households across the country.
ONS said 0.27 per cent of the population were infected on May 14, and 0.25 per cent on May 21.
It also estimated the reproduction rate of the virus between 0.7 and 1, meaning every infected person passes the disease on to seven and 10 others, on average.
Calculations can vary between scientific groups depending on how many people they swab and when.
Now, the Government say the R rate is still below the crucial one at 0.7-0.9 as a whole for the UK, meaning it hasn’t changed in almost two months.
But SAGE last week admitted the top-end estimate has risen slightly for England and warned it could be as high as 1.1 in the South West, home to Britain’s stay-cation hotspots of Devon, Cornwall and Dorset.
Keeping the rate below one is considered key because it means the outbreak is shrinking as not everyone who catches it passes it on.
Imperial College London showed about 69 per cent of those who tested positive reported no symptoms on the day of the test or the previous week, though they may have developed symptoms later.
The report provides an insight into who was infected with the virus between May 1 and June 1, comparing geography, age, sex, ethnicity, key worker status and symptoms.
Beyond the diminished rate of infection, the research found young adults aged 18 to 24 were more likely to test positive than other age groups.
These patterns were not fully explained by young people’s ethnicity, job or where they lived, therefore suggest they are are less compliant with social distancing rules.
‘Young adults appear to have maintained higher levels of social contact than other age groups during the lockdown period in England, while older age groups may have effectively shielded,’ the authors wrote in their pre-print paper.
This reinforced the need for this age group to adhere to social distancing measures to protect vulnerable friends and family, the press release from the Department of Health said.
Children aged between five and 17 years old had similar rates of infection to adults aged 25 to 44 years, indicating that children are similarly susceptible to being infected with the virus, called SARS-CoV-2.
Those who were over 65 years were the least likely to test positive. But the risks to them if they do are far greater, with a higher likelihood of severe illness and potentially death.
People of Asian ethnicity, predominantly South Asian in this study cohort, were almost twice as likely to test positive than those of white ethnicity.
The finding is in line with mounting evidence that Black, Asian and minority ethnic groups (BAME) are being hit hardest by Covid-19.
South Asians are 20 per cent more likely to die of after being admitted to hospital than white people, according to findings from University of Edinburgh last month.
The prevalence of infection across in England was highest among care home workers, 0.71 per cent, followed by health care workers 0.47 per cent. This was seven to eight times higher than those who are not in a key worker role.
Health and social care workers are more likely to be exposed to the coronavirus. And studies suggest healthcare workers from BAME backgrounds are twice as likely to catch coronavirus.
The report also showed anyone who had recent contact with a known Covid-19 case was 24 times more likely to test positive than those with no such contact.
‘Assuming that many of these contacts were work-related, these results suggest a continuing need for improved infection control in these settings,’ the report said.
It also emphasises the importance of contact tracing — seeking anyone who has been in close proximity to a positive Covid-19 case — in keeping the spread of the virus under control.
The study will now undergo peer review before a final report is published, according to the Department of Health.
Plans are currently underway for a second large-scale study, which will use antibody tests to determine how much of the general public has been infected with Covid-19 in the past.
