While the drop in daily cases from almost 55,000 on 17 July to fewer than 30,000 on Sunday was “encouraging”, Downing Street said the prime minister believes that the impact of relaxations introduced a week ago could soon start driving numbers back up again.
Step 4 of Mr Johnson’s roadmap out of lockdown - which saw an end to mandatory face-coverings and work-from-home guidance as well as the reopening of nightclubs - had always been expected to result in an increase in cases, said a No 10 spokesperson.
But crucially, the time-lag between infections, symptoms and positive tests means that the rise in cases linked to Step 4 on 19 July is not expected to become apparent for another week or two.
Even allowing for the usual dip in positive cases recorded over the weekend, the decline in numbers over the past 10 days has been steep and protracted enough to spark speculation that the UK’s wave of Delta variant infections may have peaked earlier than expected.
The high of 54,674 new cases reported on 17 July is well below the 100,000 figure described as “almost inevitable” by government scientific adviser Neil Ferguson of Imperial College London, who said the true peak could be as high as 200,000.
One theory to explain the fall has been that it reflects the end of the Euro 2020 football tournament, which saw large crowds at stadiums as well as fans gathering in pubs and in front of TVs to watch the matches. Others have suggested that the recent spate of hot weather has encouraged people to mix outdoors, where transmission is more difficult.
But the No 10 spokesperson made clear the PM was not claiming victory over the virus yet.
“The prime minister doesn’t think we’re out of the woods yet and has stressed many times before that the pandemic isn’t over,” said the spokesperson.
“We’ve said before when we moved to Step 4, that allowing large numbers of people to meet in indoor settings would have an impact on case numbers.
“We won’t have seen the impact of Step 4 yet in terms of case numbers so as we always do, we will continue to keep all the stats under review.”
Bristol University professor of paediatrics Adam Finn cautioned against letting up on efforts to reduce the spread of Covid in response to the fall in cases.
“We need to be pleased about the recent fall in daily numbers of positive tests,” said Prof Finn. “Not confident about the implications, nor certain of what may happen next, but pleased simply because the numbers have spent five days not going up even further and faster.
“That means less viral transmission and eventually fewer hospitalisations and deaths than we feared and expected a week ago.”
But he warned: “We still have enough non-immune people around to reverse this trend if we completely stop trying to avoid spreading the infection.
“Together we desperately need to keep this happening if we can. It’s a joint effort. There’s a lot we can all do. We need to test ourselves before we go to work or mix with others, always wear a mask in crowded places and when inside with others – places to avoid for now whenever possible – and, above all, get vaccinated.”
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