As the daily tally of positive coronavirus tests in the UK reached the highest level on Sunday since 4 June, at 1,715 new cases, we take a look at whether this is a true rise in infections, and what it means.

Are cases really rising?

A quick glance at UK figures for positive coronavirus tests shows a clear upward trend since early July. On 5 July 516 new cases were reported, with a rolling seven-day average of just over 546 per day, while on 26 August 1,048 cases were reported, with a rolling seven-day average of just over 1,164 per day.

Some have suggested this rise is largely down to an increase in the number of people being tested. Indeed, 126,100 tests were processed on 5 July, compared with 186,500 on 26 August. But an analysis of the figures shows this only partly explains the rise.

As Prof Paul Hunter of the University of East Anglia points out, the proportion of tests returning positive – the positivity rate – appears to be rising. Over the first seven days in July, 232 tests were done for every positive case reported and in mid August only about 164 tests were done for every positive case – although in recent weeks this appears to have stabilised.

That, experts have said, suggests infections have truly been rising. The conclusion chimes with work from the Office for National Statistics that suggested an increase in the percentage of people testing positive in July – although again it seems this rise may have levelled off.

However, experts say the figures from Sunday should be viewed with caution. While on Monday 1,406 new cases were reported they say data for the next few days will be needed to put the number of new infections in context.

What about deaths?

While infections may have risen, number of deaths from coronavirus remain low: the daily figure for UK deaths within 28 days of a positive test has not hit 20 or higher since 21 July.

Experts say there are a number of possible explanations for this, including an increase in the use of the life-saving drug dexamethasone, and that infections now seem to be more common among young people – older age is a risk factor for more severe Covid-19.

It is not yet clear if other factors, for example the virus becoming less deadly, could also be at play.

Why are infections rising?

Experts say as lockdown restrictions are eased, a rise in cases is expected. In the UK, restrictions have gradually been eased since mid May, with social “bubbles” allowed from mid June and pubs and restaurants allowed to reopen from early July.

“The key thing we have to do is get to balance, letting people get back to normal [while] keeping control of transmission,” said Prof Neil Ferguson, an epidemiologist at Imperial College London.

That, he added, means local restrictions – as already seen in Leicester and Oldham – are likely to be a feature in more areas as outbreaks occur.

How concerned should we be?

The increase in the positivity rate since July has led to concerns about further easing of lockdown – including encouraging employees to return to the workplace.

Christina Pagel, professor of operational research at University College London, said among the concerns are that few offices have windows that open and many involve sharing lifts and bathrooms.

Ferguson added that a critical moment will be the opening up of schools, adding that could lead to a rapid increase in cases of coronavirus.

While Ferguson said he did not want to be alarmist, he added there is no room for complacency. “We do need to make sure that our testing, tracing and response to outbreaks in workplaces and schools or wherever is up to scratch,” he said.

Prof Rowland Kao, an epidemiologist at the University of Edinburgh, agreed, noting “sparks” of coronavirus are to be expected. “How you respond is what matters,” he said.

Additional reporting by Natalie Grover