Covid: All the scientific theories on why cases are dropping in the UK

The number of new coronavirus cases recorded in the UK fell for the sixth successive time on Monday, marking the first time this has happened since November during England’s second national lockdown.

Scientists were pleased, if a bit surprised, after the latest daily count came in at 24,950 – down from more than 42,000 a week ago and the lowest the figure has been for three weeks.

The news was especially welcomed after Sajid Javid, the health secretary, predicted Britain would see cases rise to 100,000 per day during the summer – an estimation some experts said was too optimistic.

“The recent fall in cases in England is great news, but also puzzling given that progressive relaxation of restrictions has occurred,” Stephen Griffin, a virologist at the University of Leeds, told the Financial Times.

“We need to be pleased about the recent fall in daily numbers of positive tests,” Adam Finn, a professor of paediatrics at the University of Bristol, added to the paper. “That means less viral transmission and eventually fewer hospitalisations and deaths than we feared and expected a week ago.”

Meanwhile, immunologist Professor Peter Openshaw said that while he was “cautiously pleased” to hear cases were dropping, further daily data would show if it was a sustained trend or “just a blip”.

Prof Openshaw, who sits on the government's New and Emerging Respiratory Virus Threats Advisory Group (Nervtag), told BBC R4’s PM Programme: “It is exciting to see those rather encouraging figures, but there have been some delays in reporting the figures and we’re still waiting for the full data to be released by the Office for National Statistics.

“So, let’s not get overexcited.”

Some experts believe the supposed drop in cases is due to the lag in health data recordings since 19 July, dubbed Freedom Day, when coronavirus lockdown measures were thrown out in England.

Paul Hunter, a professor of medicine at the University of East Anglia, said on Monday “it [would] not be until about next Friday before the data includes the impact” of the 19 July unlocking.

“The data at present is looking good for at least the summer,” he told the BBC, before warning: “Today’s figures do not, of course, include any impact of last Monday’s end of restrictions. It will not be until about next Friday before the data includes the impact of this change.”

Public Health England (PHE) has warned of various delays to data being collected since the beginning of the pandemic – just yesterday, for instance, the agency’s daily update on Covid cases, deaths and vaccines included a cautionary message that “today’s update to the #COVID19 Dashboard is experiencing a delay”.

It meant the number of deaths to have occurred in the past 24-hour period were not known until later in the evening, which is a common occurrence on Monday across the UK as health bodies scramble to collect data from over the weekend.

Another obvious explanation for the significant drop in Covid cases is last week’s heatwave, experienced by much of the UK. A rise in people meeting outside – where it is harder for the virus to transmit – is likely to have played some part in cases reducing.

Epidemiologists advising the government have consistently said that socialising outdoors helps minimise infection risks, though perhaps not enough to explain the scale of the recent drop.

The so-called “pingdemic” could also be driving down cases. Hundreds of thousands of people have been forced to isolate by the NHS Covid app in recent weeks, after being pinged for unknown reasons as the app gives no detail of where it is a person supposedly came into contact with the virus.

As intended, this has helped stem the spread of the virus. However, frustration with being pinged is said to have caused dozens of people to delete the app altogether. Polls last week suggest more than a third of British people – younger people, who are less likely to be fully vaccinated – have removed it from their smartphone to avoid being told to stay at home.

The end of the school year is thought to be a contributor to declining cases, as less children will need to test themselves so frequently. The same can be said for the end of big sporting events, such as Wimbledon and the Euros, being hosted in England.

“It never occurred to me that the Euros would have as big an impact as they seem to have had,” Prof Hunter told the FT. “Ironically, that may make the next six months a little easier,” he added, likely referring to the herd immunity that may have been generated among spectators.

A No 10 spokesman has described the fall in coronavirus cases as “encouraging” but said numbers were still expected to rise, adding that “the prime minister thinks we’re not out of the woods yet”.

Professor Neil Ferguson, whose modelling led to the first lockdown in March 2020, echoed this message in an interview with BBC R4’s Today programme earlier, though he provided a positive outlook for autumn.

“We need to remain cautious, especially with the potential increase in contact rates again as the weather becomes less fine and schools return,” he said. “We're not completely out of the woods, but the equation has fundamentally changed. The effect of vaccines is hugely reducing the risk of hospitalisations and death.”

But he added: “I'm positive that by late September or October time we will be looking back at most of the pandemic. We will have Covid with us, we will still have people dying from Covid, but we'll have put the bulk of the pandemic behind us.”

Despite the decline in cases, NHS data published on Monday showed a total of 5,055 patients were in hospital with Covid-19 in England – up 33 per cent from the previous week and the highest it has been since mid-March.

Dr Mike Tildesley, a member of the Scientific Pandemic Influenza Modelling group (Spi-M) advising ministers, told the PA news agency it takes a couple of weeks before case numbers in the community are reflected in hospital admissions

The time lag between infections and people being admitted to hospital, mean admissions are likely to rise in the coming days regardless of the number of cases, he said.

Meanwhile, NHS Providers, which represents hospital trusts, said a combination of pressures were being experienced by the health service and that things will only get worse before they get better.

It called on ministers to make “the right decisions” over the next month as it finalises NHS funding for the second half of the financial year.