The UK’s lockdown appears to be blocking the spread of the coronavirus so well that it could drive the outbreak to an early end, scientists say.
Researchers say each infected patient may now only be passing COVID-19 on to 0.62 others, on average, down from 2.6 each before people were forced to stay at home.
A virus must have a reproduction number – known to scientists as an R0 (R-nought) – of more than one for an outbreak to be able to carry on.
If it’s prevented from spreading on at least a one-to-one ratio it will quickly run out of new victims and the epidemic will come to an end if the R0 can be kept down.
Scientists at the London School of Hygiene and Tropical Medicine said the virus may now be struggling to spread because people have around 73 per cent fewer daily contacts than they did before the lockdown started.
The empty streets around Waterloo station on April 01, 2020 in London. COVID-19 has claimed more than 40,000 lives and infected hundreds of thousands more
Karol Sikora, British oncologist and professor of medicine at the University of Buckingham, said the virus will ‘burn out’ if social distancing is kept up
The R0 is simply the number of other people that the average coronavirus patient infects.
A higher number means a faster spreading outbreak, and a number lower than one means the outbreak will run out of steam and be forced to an end.
The London School of Hygiene (LSHTM) researchers made their estimate using an online survey of 1,300 people who were all asked to list what human contact they had had in the past 24 hours.
This was compared to a similar survey done in 2005-2006 to give an idea of how social contact now compared to normality.
They found people now have 73 per cent fewer daily encounters and adjusted the coronavirus’s R0 accordingly using a computer algorithm.
Dr Jennifer Cole, from the Royal Holloway university in London, was not involved in the study but said: ‘Once the R0 is below 1, the disease will eventually peter out.
‘How quickly depends on how far below 1 the rate can be pushed.
‘It is important to remember that cases will still rise in the short-term as people who were already infected before the lockdowns were implemented may not yet have developed symptoms.’
She added: ‘It is also valuable that this study shows that R0 can be reduced significantly even when people are still allowed to go out for essential food and medicines and with essential workers still operating.’
The researchers hope that their online survey of social contact is representative of the whole country.
‘If we see similar changes across the UK population, we would expect to see the epidemic to start to decline,’ said Professor John Edmunds, who led the research.
‘However, our estimates are not to be read as “job done”.
‘Rather, they should be used as motivation for us all to keep following UK government instructions.’
Professor Edmunds said that it’s now ‘imperative’ that British people ‘don’t take our foot off the pedal’.
‘We must continue to stop transmission of the virus to reduce the burden on the NHS now and over the coming months,’ he said.
If an epidemic ends because the virus is forced to stop spreading, the protection ends when social distancing measures are lifted.
Areas outside of the shutdown would not benefit from a low R0 – it does not make the virus any less infectious – and the country would remain at risk of future epidemics.
The UK suffered a record-breaking 563 coronavirus deaths in just 24 hours on Wednesday, bringing the country’s total death toll to 2,352.
Customers observing social distancing in the queue for a supermarket in Westminster, London as the UK continues in lockdown to help curb the spread of the coronavirus
But now the public is urged to keep up their social distancing efforts at a crucial time.
People have been told not to go outside unless it is necessary or they are exercising away from other people, and everyone should work from home if they can.
They can still shop for essentials – only supermarkets, pharmacies and convenience stores remain open – but cannot go out for fun. Restaurants, pubs and cafes are shut.
Those who are outdoors should stay 2 metres (6 feet) away from other people at all times and wash their hands when they get home.
‘Today’s death toll is tragic,’ said British Oncologist Professor Karol Sikora. ‘But please, don’t think the lockdown is useless. It will work.
‘With the long incubation period of the virus it will take some time before we see the benefits. Staying at home does make a huge difference.’
Professor Sikora said the new reproduction number of just 0.62 means the virus is ‘cornered’.
‘It has nowhere to go and will burn out,’ he tweeted on Wednesday.
The LSHTM team’s research suggests that the reproduction figure now would be in a range between 0.37 and 0.89 with the most likely value being 0.62.
The researchers acknowledge limitations of their work, which has not been reviewed by other scientists.
One limitation is that it’s based on people’s lifestyles in 2005 and 2006, which may be different to life in 2020, and that it cannot accurately measure children’s movements.
Because individuals also reported their contacts a day later, they may not have remembered them all, or could have given misleading data, they said.