The apparent fall in Covid-19 case numbers may be temporary ahead of a return to 'exponential growth', experts have warned.

By 9am on Thursday, there had been a further 39,906 lab-confirmed Covid-19 cases in the UK - down from 44,104 at the same time on Wednesday.

Paul Hunter, professor in medicine at the Norwich School of Medicine, University of East Anglia, said Thursday was the first time reported case numbers had been lower than the same day the previous week since early May.

But he said it is too early to tell what affect the relaxation of restrictions on July 19 is going to have.

Prof Hunter said of Thursday's figures: "They represent a 18 per cent drop. Also the week-on-week percentage increase in cases has fallen from a peak of 43 per cent last Sunday to just 24 per cent today.

Tube passengers still choosing to wear a mask after Freedom Day
Tube passengers still choosing to wear a mask after Freedom Day

"But it is still too early to see any impact of the relaxations of Monday 19 and some of the reduction in cases will be because of many children no longer being tested as regularly now schools are closed.

"I would caution that this may just be a temporary slowing in reports before we start to see a return to exponential growth towards the end of next week as a result of the ending of restrictions last week," he said.

Prof Hunter said we will not know for certain until August 9 - three weeks after so-called "freedom day".

intensive care
By 9am on Thursday, there had been a further 39,906 lab-confirmed Covid-19 cases in the UK (file photo)

"But there are some positive signs. If you look at the course of the Delta epidemic from early May it was clear that the rate of increase in cases was already slowing by June.

"But there was a significant acceleration in new cases about eight to 10 days after the first England game in the Euros.

"There was also a subsequent acceleration around the same time after the quarter-finals. But after both events the increase started slowing fairly soon after that despite the fact that the games were continuing.

"Also, in Scotland case numbers started to fall about 11 days after they left the championships and case numbers have continued to fall since.

Two people hug in the middle of the dancefloor at Egg London nightclub in the early hours of July 19
Two people hugging in the middle of the dancefloor at Egg London nightclub in the early hours of July 19

"If such a perturbation as the Euros caused only a temporary acceleration in the increase in case numbers despite games continuing, this may bode well for the impact of 19 July, it could suggest we will see only a short-term boost towards the end of next week followed by slowing or even a decline in the days following. Time will tell."

Professor John Edmunds, a member of the Scientific Advisory Group for Emergencies (Sage), which advises ministers, told the PA news agency: "School closure, which occurred in Scotland on 23 June and has been occurring in the rest of the country more recently, will start to have an effect.

"In addition, the enormous numbers of adults and children self-isolating over the last few weeks should also help slow epidemic growth.

"On the other hand, it must be remembered that the effect of loosening restrictions earlier this week will not be apparent in the epidemiological data yet.

"So it is difficult to say exactly what will happen. What does seem pretty likely though is that if we do not take any further action we are in for an extended period of high incidence with all the disruption and risk of hospitalisations and deaths that that entails."

Clubbers queueing in Brighton
Clubbers queueing in Brighton

Asked what further action would be a good idea, Prof Edmunds said vaccinating secondary school children would "help enormously".

Dr Simon Clarke, associate professor in cellular microbiology at the University of Reading, said: "It is probably premature to suggest that we are seeing a levelling-off of infections based on today's data.

"Numbers of infections over the past year have shown big rises and falls much like today, and so it's wise to look at the trends rather than getting too excited about daily numbers.

"We have not yet seen the effect of lifting of final restrictions on 19 July on numbers, nor have we yet seen how school summer holidays may take some heat out of the infection numbers.

"However, any good news about lower cases as schools close can expect to be reversed come September.

"It remains the case that mixing of people will remain the most significant driver of infection numbers, while vaccinations will have the largest effect to reduce those numbers.

"Of course, the vaccines are not 100% effective at reducing transmission, and the virus cannot spread at all without social interactions, so ongoing care needs to be taken while numbers are still high."