Though death tolls have remained low, the weekly rate of new cases in the UK has now risen above 20 per 100,000 people.
Sunday saw the largest rise in cases since May 22 with almost 3,000 positive cases reported.
In an interview with Sky News about his concerns around a second wave, World Health Organisation’s Dr David Navarro said: ‘I’m afraid it’s coming. I don’t like calling it a second wave but I believe there are going to be more spikes and indeed some surges in cases, because the virus hasn’t changed.
‘It’s the same virus that came and caused so much trouble earlier this year, and it’s just been lurking.
‘We’ve been very good at holding it back through restricting movement and lockdowns.
‘But now as life gets going again and younger people are going to university, also there is some movement with holidays and of course work, then I’m afraid it does mean that the virus is going to come back.’
Professor of public health at the University of Edinburgh Linda Bauld said where the infection rates previously appeared to be contained in certain parts of the country, it has now become a UK-wide phenomenon.
She said: ‘We’re seeing case numbers rising in Northern Ireland, Wales, and in the west of Scotland.
‘Rising cases is not a feature of more testing; these are genuine, additional cases.
Across the UK, local lockdowns have been imposed in numerous cities in Bradford, Greater Manchester, to Leicester, in a bid to clamp down on soaring infection rates.
Leeds was added to Public Health England’s weekly watchlist of concerning areas last week after its seven-day infection rate increased to 29.4 cases per 100,000 people.
She added: ‘I’m not panicking, because I think we really know how to protect our care homes and vulnerable groups now.
‘But we really need to try and make sure it doesn’t escalate well above where we are now, because I think then the Government has limited ability except to close things again and we all wish to avoid.’
Dr Navarro’s comments come a day after England’s deputy chief medical officer professor Jonathan Van-Tam also expressed ‘great concern’ over the spike in Covid-19 cases.
Almost 3,000 additional cases were reported on Monday, and several schools in England and Wales have reported outbreaks.
In an interview with LBC, Health secretary Matt Hancock attributed the sharp increase to ‘affluent young people’ who weren’t observing social distancing rules, a pattern he said was observed in France and Spain.
New social distancing measures have banned gatherings of over 30 people, and the number of people allowed inside your homes is expected to be decreased.
Speaking to BBC Radio 1’s Newsbeat, Mr Hancock urged young people who might be carrying the virus but are asymptomatic ‘don’t kill your gran.’
Professor Bauld added she was ‘deeply concerned’ infection rates could worsen as the weather gets colder.
‘I don’t like the term second wave because we never moved out of the first one. The virus never went away, we didn’t suppress it to zero.
‘But we are at risk of seeing a very significant rise. My own personal view is that we will not see that translate to large numbers of deaths.
‘I think people can still become very unwell with the virus even if they unfortunately don’t pass away, and I think the health services are going to be challenged in the next few months.’