China has recorded its deadliest day so far in the coronavirus outbreak, as authorities braced for millions of people to return to work on Monday after the lunar new year break in a new test of the nation’s containment strategy.

At least 813 people are reported to have died from the disease, most of them in mainland China, according to official data released on Sunday which showed that the previous day’s toll was the highest yet at nearly 90.

However, the number of new infections reported per day in China has fallen significantly, leading health officials to declare their containment measures were starting to work.

The end of the new year break, which was extended by 10 days to try to prevent the virus from spreading, is likely to be a crucial moment.

“[If] there’s a bump when people go back to work at the beginning of this week, then we’ll know we’re in trouble and then we have to back off again,” said Ian Lipkin, the director of Columbia University’s Centre for Infection and Immunity, at a press conference on Sunday.

Chinese cities have appeared deserted in recent weeks as much of the country was ordered into virtual lockdown, flights were cancelled and schools and workplaces were shut. A large number will remain closed on Monday and many white-collar employees will work from home.

China’s cabinet said on Sunday it would coordinate with transport authorities to ensure the smooth return to work of employees in key industries such as food and medicines. The State Council’s special coronavirus group also said workers should return in “batches” rather than all at once, in order to reduce infection risks.

The updated coronavirus death toll surpassed that of the 2002-3 epidemic of severe acute respiratory syndrome (Sars), which killed 774 people.

Joseph Eisenberg, a professor of epidemiology at the University of Michigan, said it was too early to say whether the coronavirus epidemic was peaking. “Even if reported cases might be peaking, we don’t know what is happening with unreported cases,” he said.

In the UK, a plane carrying British citizens evacuated from the Chinese city of Wuhan landed in Oxfordshire on Sunday. The flight, with more than 200 people onboard including some foreign nationals, arrived at RAF Brize Norton shortly before 7.30am.

The Foreign Office said it was the second and final flight to be chartered by the UK and had government staff and military medics onboard. The passengers were being taken to the Kents Hill Park hotel and conference centre in Milton Keynes to be quarantined for 14 days.

On Sunday night French health officials said that cases detected in the UK and Mallorca were linked to “cluster” in a French ski resort.

Spain’s National Microbiology Centre said test results had confirmed the Mallorcan case, the country’s second, in the early hours of Sunday morning. The Balearic Islands health department said the British man, his wife and two daughters had gone to Mallorca’s Son Espases hospital on Friday after one of them began feeling ill. The infected man is being kept in isolation, and his wife and children have tested negative for the coronavirus and are displaying no symptoms.

A spokesman for Spain’s health ministry said the man had previously been at a French ski resort. Five Britons including a nine-year-old child have tested positive for the virus in France. Another six UK nationals are being kept under observation in French hospitals.

The group had been staying in two apartments in a ski chalet in the village of Contamines-Montjoie, in the eastern French Alps, when they were visited by a Briton who had been in Singapore and was later found to have the virus when he returned to the UK at the end of last month. Another UK case which emerged on Sunday is also linked to the group.

The French health minister, Agnès Buzyn, visited the ski resort on Sunday as officials went into damage-limitation mode at the start of the school half-term holidays. It is the busiest time of the year for French mountain resorts, and tourist officials in the Haute-Savoie region sought to calm the growing sense of alarm.

“We’ve had many phone calls this morning. There are a few cancellations; people are panicking a little and asking where the contaminated people have been. It’s normal,” said Annick Roger, the director of the Contamines-Montjoie tourist office.

There was little sign of panic on Sunday in the village near Mont Blanc, whose population is swelled by tourists every winter high season. Olivier Campion, a French visitor to the resort, told Agence France-Presse: “I was supposed to go to China for work and I postponed my visit. Instead, I didn’t have to go so far to find the virus.”

Eric Paris, who runs the village pharmacy, said there had been a sudden demand for face masks but he was refusing to hand them out. “It’s been 14 days and the incubation period has passed. If everyone starts walking around in masks, can you imagine the trauma?” he said.

Paris added: “I’ve consulted the regional health authorities and the town hall and there has been no instructions. Everyone who might have been contaminated in Contamines has already been. Just because someone is full of aches after a day skiing doesn’t mean they have the coronavirus.”

Authorities set up a crisis centre in the village and said a school that the infected nine-year-old attended and a second school in nearby Saint-Gervais, where the child spent an afternoon taking an extra French lesson, would remain shut next week.

Spain confirmed its first case of coronavirus on 31 January after a man was diagnosed on the remote La Gomera island in the Canaries. The patient is part of a group of five people in isolation and under observation on the island after it emerged that they had come into contact with a German man diagnosed with the virus.

More than 37,100 people are now confirmed to have been infected worldwide, with a jump of 2,147 in Hubei province since Friday. The deaths include that of Li Wenliang, a doctor who was one of the first people to raise the alarm about the virus.

The only people to have died outside the Chinese mainland are a Chinese man who died in the Philippines and a 39-year-old man in Hong Kong.

Around 3,600 passengers and crew onboard a cruise ship in Hong Kong were permitted to disembark on Sunday after testing negative for the virus. They had been quarantined since Wednesday amid fears some crew might have contracted the virus on an earlier voyage.

Another cruise ship with dozens of confirmed cases aboard remains in quarantine off Japan. Princess Cruises, the operator of the Diamond Princess cruise ship, said a further six people had tested positive, bringing the total number of cases onboard to 70.

Brazil evacuated more of its nationals from Wuhan on Saturday, with 34 people flown from China to an air force base in Anápolis, 90 miles from the capital, Brasília, where they will remain in isolation for 18 days.

Reuters contributed to this report