The number of coronavirus cases in the UK is doubling roughly every seven days, according to the country's chief scientific advisor, Patrick Vallance. If that rate continues to grow unabated, "by mid-October you would end up with something like 50,000 per day," which "could lead to 200 deaths a day" by November, Vallance warned at a Monday press briefing.
"If we don't act, the virus will take off," Vallance's colleague Chris Whitty, the UK's chief medical officer, told the same briefing in Downing Street. "That is the path we are on and if we do not change course, we will find ourselves in a difficult problem."
The advisors' comments have fueled speculation that the government is preparing the ground for a second national lockdown, or other hard measures, in order to get cases back to a sustainable level.
"In ... the next six months, I think we have to realize that we have to take this collectively very seriously," Whitty said, adding that the country had turned a corner "in a bad sense."
Prime Minister Boris Johnson is expected to make a statement to the country later this week.
Vallance and Whitty's warnings come as the UK faces a difficult autumn. Covid cases have risen since full lockdown measures were lifted early in the summer, and on Monday Whitty warned: "The seasons are against us."
On Sunday alone, 3,899 confirmed infections and 18 deaths were reported in the UK.
The rise in cases has already led to local lockdowns and emergency measures in numerous parts of the country. Over the weekend, the government announced that people breaking quarantine and self-isolation measures in England could face fines of up to £10,000 ($12,800).
Johnson and members of his government have previously indicated that a second national lockdown would be a last-ditch scenario. Back in March, Johnson locked down the country later than many of his European counterparts. He did so reluctantly, knowing the economic damage it would cause. As a result, he was criticized for acting too late.
Johnson's government has also been criticized for not having a good enough testing regime, meaning that local and health authorities were acting blindly as they tried to protect those most vulnerable.
If cases continue to rise, these criticisms are likely to give the PM more headaches, as he weighs up the long-term costs of shutting down the economy for a second time. Stories are appearing almost daily of people having to travel many miles for a coronavirus test.
Unfortunately for Johnson, it's very likely cases will stay high.
The autumn and winter months are particularly dangerous, as colder weather encourages indoor gatherings rather than those in the open air, where transmission of the virus is less likely.
Unlike during the previous lockdown, and the summer months that followed, children are now back in school, where enormous networks of contacts can be formed, expediating the spread of the virus.
And as of this week, universities are welcoming students, meaning hundreds of thousands of young people are traveling across the country to mix in high-volume accommodation. In recent weeks, government data has shown that infections are particularly high among young adults, who are less likely to suffer the worst Covid-19 symptoms, but can still pass it on to those who are more vulnerable.
If the UK is unable to get the virus under control, Johnson could find himself in a pretty unenviable position in just a few weeks. From being the Covid-19 capital of Europe to having the worst recession of any major economy, this is a country that has already lost a year to the virus.
The public largely obeyed the government's rules the first-time round. But the fact that the UK has the highest number of deaths in Europe and the widespread criticism of the government's handling of the virus leaves a question mark over whether they'd follow Johnson's orders a second time.
If they don't, the virus will continue to spread and the PM could find himself addressing the nation in December, asking them to do something no British Prime Minister can have imagined in their worst nightmare: Cancel Christmas.