There were reports of “panic shopping” at British supermarkets ahead of the holiday season, as Britons watched televised scenes of massive traffic snarls of cargo trucks headed into the port of Dover.

France and a number of other nations on Sunday imposed far-ranging travel bans on arrivals to the continent from Britain, after the health minister said a new coronavirus mutation — spreading faster than other variants — was “out of control.” More than half of all newly diagnosed cases in London, for example, were caused by the variant.

British authorities said they currently do not believe that the new mutation is more deadly or vaccine resistant, but claims of a much higher transmissibility have alarmed governments in Europe and beyond.

Even if the strain is no more likely to cause disease, a surge in new infections will still send more people into hospitals and ICUs, and eventually cause more deaths.

Adam Finn, professor of pediatrics at the University of Bristol, said Monday that the new strain was already being tested to see if it might be more resistant to vaccines. “It is a matter of immediate interest,” he said, adding that “the predictions are that it have likely have either no effect or a minor effect” on the efficacy of vaccines.

Tobias Kurth, the director of the Institute of Public Health at Berlin’s Charité University Hospital, said the decision by numerous countries to “pull the emergency brakes” and suspend travel with the U.K. is “understandable.”

But Kurth cautioned that the mutation is “certainly already in continental Europe, and likely in Germany.”

“We won’t be able to stop it,” even though travel restrictions may slow the spread of the mutation, he said.

Similar mutations of the virus that share traits with the British variant have been detected in South Africa and Holland.

Hong Kong and India announced Monday that they will also suspend flights from Britain, following similar decisions by Canada, Israel, Turkey and countries across Europe.

The British government said it would begin to assist British travelers stranded abroad. Earlier, Prime Minister Boris Johnson announced his first trip overseas in January would be to India. His official spokesman on Monday declined to say whether it would be canceled.

Johnson scheduled a meeting of his emergency cabinet on Monday afternoon to coordinate a response to the international travel bans. Because of soaring cases, many stoked by the new variant, Johnson ordered London and parts of the southeast England into Tier 4 lockdown on Sunday, telling 18 million people to “stay at home” and only venture out to shop for food and medicine, attend medical appointments or do outdoor exercise.

Meanwhile, French Transport Minister Jean-Baptiste Djebbari tweeted that, in coordination with other European nations, the country would “put in place a robust sanitary protocol to allow traffic flows from the United Kingdom to resume,” with details to be announced as early as Monday afternoon.

But it remained unclear whether the measures would apply to freight traffic and be sufficient to prevent a pileup of perishable goods on the British side of the English Channel. The European Union was expected to hold talks on Monday to coordinate on how to proceed, as some of its members continued to curtail travel with Britain.

On Monday morning, Denmark and Poland joined more than a dozen other European countries, including Germany, Italy and Netherlands, in banning flights from Britain — although some European officials acknowledged that the efforts may come too late.

French Health Minister Olivier Véran said Monday morning that the new variant may already be in France. Italy, the Netherlands and Denmark said they have identified the mutation among recently discovered coronavirus cases in their countries. Israel and Turkey included Denmark in newly imposed travel bans over the weekend.

But the biggest disruptions were expected along the French and British sides of the English Channel. France suspended passenger and accompanied freight traffic, imposing a far more comprehensive ban than the border closures that were introduced during the first wave of the virus in spring.

The passage from Britain to France is one of the most important transport corridors in Europe, which means that food and other time-sensitive cargo may end up rotting on the side of British roads in the coming days.

Even though the restrictions do not ban trucks from entering the United Kingdom, industry representatives cautioned that few companies would be willing to take the risk of then becoming stranded there, meaning that traffic is likely to be heavily impacted in both directions.

“No driver wants to deliver to the U.K. now, so the U.K. is going to see its freight supply dry up,” said Vanessa Ibarlucea, a spokeswoman for the French road haulage federation, according to Reuters.

A major British supermarket group voiced similar concerns. “If nothing changes, we will start to see gaps over the coming days on lettuce, some salad leaves, cauliflowers, broccoli and citrus fruit — all of which are imported from the continent at this time of year,” British supermarket chain Sainsbury’s warned in a statement on Monday.

Shapps, the British transport secretary, maintained there was no immediate risk of food shortages, partially because the government had been “ready for a degree of disruption” due to the possibility of a “no-deal” Brexit. Shapps also told Sky News that the entry ban “won’t have an impact on the vaccination program.”

The border disruptions come less than two weeks before Britain is set to cut its last membership ties with the E.U., despite both sides having been unable to agree on a trade deal. One of the most widely feared impacts of a “no-deal” Brexit are widespread disruptions along Britain’s borders — a scenario that on Monday appeared to have already materialized and that could put additional pressure on Prime Minister Boris Johnson, who is under criticism for his handling of Brexit negotiations and the coronavirus pandemic.

British officials on Sunday announced 35,928 new coronavirus cases, nearly double the number from a week earlier. Health officials said the sharp increase was of serious concern but that it was too early to know whether it was linked to the new variant.

As cases mount, Britain on Saturday announced increased pandemic restrictions, reversing earlier hopes for a more relaxed holiday period.