The coronavirus variant that was first identified in the United Kingdom in September and has swept the country and beyond in recent months is not only more transmissible but also deadlier than earlier variants, a new study has confirmed.

The B.1.1.7. strain has spread to more than 60 nations – including China, where the pandemic began more than a year ago –according to the World Health Organization (WHO). Several countries have also moved to block air travel from the U.K., and the U.K. has halted flights from Brazil and South Africa.

Researchers tracked roughly 1 million individuals tested for COVID-19 from November to January in community settings, including about 3,000 who ultimately died from it. After accounting for other factors that affect COVID-19 outcomes, patients with the new variant had a roughly 35% higher risk of death, they reported on medRxiv ahead of peer review.

Among male patients aged 55-69, around 1-in-180 died after becoming infected with older versions of the virus.

With the new variant "that's gone up to around ... 1-in-140," said co-author Nicholas Davies of the London School of Tropical Medicine & Hygiene to Reuters. The absolute risk of death remains low under age 54, his team said.

For women aged 70-84, the risk of death within 28 days went from 2.9% with the original variant to 3.7% with the new U.K. variant, and for those aged 85 and older it went from 12.8% to 16.4%. For males aged 70-84, the mortality rate rose from 4.7% to 6.1% and for older males from 17.1% to 21.7%.

The researchers did not have data on people who were diagnosed in hospitals or on infected people who were never tested. Davies said his team is updating its analysis with more data, "and it looks like the increase in mortality may well be higher than 35%."

The findings echo previous statements by British government officials. Prime Minister Boris Johnson had warned of the possibility in a Downing Street news conference in January.

Most recently, the government’s chief scientific adviser Patrick Vallance told a news conference that "there is evidence that there is an increased risk for those who have the new variant."

Vallance said that for a man in his 60s with the original strain of the virus, "the average risk is that for 1,000 people who got infected, roughly 10 would be expected to unfortunately die."

"With the new variant, for 1,000 people infected, roughly 13 or 14 people might be expected to die," he said. However, he stressed that "the evidence is not yet strong" and more research is needed.

In contrast to that uncertainty, he said, there is growing confidence that the variant is more easily passed on than the original coronavirus strain. He said it had a higher viral load and appears to be between 30% and 70% more transmissible.

Maria Van Kerkhove, the World Health Organization's technical lead on COVID-19, said studies were underway to look at the transmission and severity of new virus variants. She said so far "they haven’t seen an increase in severity" but that more transmission could lead to "an overburdened health care system" and thus more deaths.

Paul Hunter, a professor in medicine at the University of East Anglia, said, "The conclusion about this probable increased lethality comes from analyses made by several different groups, though working with essentially the same data."

"There is quite a bit of difference in the estimated increased risk of death between the different analyses, though most but not all show increased risk of death," he told Agence France-Press (AFP).

Ian Jones, professor of virology at the University of Reading, said: "The data is limited and the conclusions preliminary. However, an increased case fatality rate is certainly possible with a virus that has upped its game in transmission."

British officials say they are confident that the vaccines that have been authorized for use against COVID-19 will be effective against the new strain identified in the country. But Vallance said scientists are concerned that variants identified in Brazil and South Africa could be more resistant to vaccines, adding that more research needs to be done.

The U.K. is currently in a lockdown in an attempt to slow the latest surge of the coronavirus outbreak. Pubs, restaurants, entertainment venues and many shops are closed, and people are required to stay largely at home. The number of new infections has begun to fall, but deaths remain agonizingly high, averaging more than 1,000 a day, and the number of hospitalized patients is 80% higher than at the first peak of the pandemic in the spring.