A second wave of the coronavirus is "highly likely" this autumn or winter, the top scientific body in France has said following a rise in cases.
The warning comes as German doctors also said the country is already dealing with a second spike of infections because people were flouting social distancing rules.
Both France and Germany are currently on the UK government’s list of “air bridges”, which means people arriving in England from those countries do not have to quarantine for 14 days upon their arrival.
The warnings came as the World Health Organization (WHO) said the virus is surging back in most countries that previously had it under control.
France’s health ministry said in a statement: “France has the situation under control but it is precarious with a surge of virus circulation this summer. The short-term future of the pandemic mainly lies in the hands of the population.
"It is highly likely that we will experience a second epidemic wave this autumn or winter."
On Monday, France reported 3,376 new confirmed cases over the previous three days, with the number of people being treated in intensive care units for the disease also creeping higher.
The seven-day moving average for new cases has held above the 1,000 threshold for the fifth day in a row, meaning the country is experiencing an infection rate not seen since the two-month lockdown.
In Germany, Susanne Johna, president of the Marburger Bund doctors union, told the Augsburger Allgemeine newspaper there was a danger that a longing to return to normality would damage the success Germany had achieved so far in restricting the spread of the virus.
"We are already in a second, shallow upswing," she said.
The number of daily confirmed coronavirus cases in Germany has risen steadily in recent weeks, with health experts warning lax adherence to hygiene and distancing rules among some people is spreading the virus across communities.
The number of confirmed cases in Germany increased by 879 to 211,281, data from the Robert Koch Institute (RKI) for infectious diseases showed on Tuesday.
In the UK, there were 938 new COVID-19 cases confirmed on Monday. Overall, a total of 305,623 cases have been confirmed.
Virus ‘capable of surging back really quickly’
On Tuesday, Dr David Nabarro, the WHO’s special envoy on COVID-19, warned on BBC Radio 4’s Today programme: “This virus is capable of surging back really quickly and is actually doing so in most countries where there’s been success at getting it under control.
“As it surges back, the way you stop outbreaks developing is through having well-functioning contact tracing linked to testing, with isolation of people who’ve got symptoms or who’ve been in contact.
“If we can do that, and do it well, then the surges are kept really small, they’re dealt with quickly and life can go on.
“If, on the other hand, this testing and tracing and isolation just is not done properly, then you get very bad surges occurring and this will lead to economic challenges.”
Additional reporting by Reuters.