At a news conference from 10 Downing Street, British Prime Minister Boris Johnson said the new variant “may be up to 70 percent more transmissible” than previous versions of the virus here.
“This is spreading very fast,” he said, announcing local and international travel bans and other extreme measures for about 18 million people in England beginning Sunday. Wales and Scotland followed with their own tightened restrictions, including banning all but essential movement around the isle.
Many countries have reimposed tough social distancing measures as coronavirus cases roared back in second and third waves. Britain, however, appears to be the first to point to a specific coronavirus variant for a surge in infections and the need to bring back the toughest measures.
“We have alerted the World Health Organization and are continuing to analyze the available data,” said England’s chief medical adviser, Chris Whitty. It was not immediately clear if the new variant had moved beyond Britain.
Britain’s chief science adviser, Patrick Vallance, said the “virus has taken off” after being observed for months.
“And it’s moving fast and has led to a sharp increase in hospitalizations,” he said, calling the need for new restrictions a “horrible moment.”
He went on, however, to say that the outbreak of the new strain “is controllable and there is light at the end of the tunnel with the vaccinations having started.” Britain was the first to approve the new Pfizer-BioNTech vaccine and the first to begin a mass immunization program earlier this month.
The researchers stressed that this kind of mutation is not surprising. Sharon Peacock, director of the Covid-19 Genomics UK Consortium and a professor of microbiology at the University of Cambridge, stressed that thousands of mutations in the coronavirus have been identified since it emerged.
“The vast number have no impact,” she said. “Mutations are a part of natural life.”
Many viruses mutate and evolve, becoming more transmissible but less deadly. But to date, the decline in mortality among infected people during the pandemic has been attributed to improvements in treatments.
Johnson and his government have been fighting to “save Christmas.” They put Britain in countrywide lockdown in November, hoping that would slow transmission and allow for a greater relaxation of restrictions for a five-day period during the holidays, to allow families and friends to gather.
Now London and the southeast and east of England will enter the highest level of “Tier 4” restrictions.
That means all nonessential shops will be closed, as will gyms, hair salons, pubs, restaurants and theaters. Travel to and out of the Tier 4 areas will not be allowed. People should leave their homes only to shop for food and medicines, attend medical appointments, take outdoor exercise and travel to and from work, if they cannot work from home. Gatherings are banned, though there are exceptions for religious services. People will be able to meet only one other person from another household in an outdoor space only.
Christmas gatherings of more than one family will be banned in the Tier 4 zone — but permitted for one day in other areas.
“We, of course, bitterly regret the changes,” Johnson said.
“When the virus changes its method of attack, we as a country have to change our method of defense,” he said.
British scientists have been following the spread of the new variant for nearly three months, eventually seeing it in samples taken from more than 1,100 people, most of whom lived in the southeast of England.
John Edmunds, an infectious diseases expert at the London School of Hygiene & Tropical Medicine, told reporters that scientists need to answer three questions: Is the variant more deadly, can it bypass previous infection antibodies or vaccination, and is it transmissible?
“At present we have no information on the first two questions, but over the last few days we have begun to get an answer for the third, and the answer is very bad news,” he said. “It looks like this virus is significantly more infectious than the previous strains.”
On Saturday, the chief science adviser said there were 23 different mutations in this new variant. Most were in a segment of the virus’s genome that encodes for the spike protein, the protruding structure essential to the pathogen’s ability to bind with the receptor cells in a person who gets exposed and then infected.
The virus trackers briefed reporters from various media, including The Washington Post, in recent days. What surprised them was the sudden prevalence of the variant.
“This lineage came up quite rapidly,” said Nick Loman, a professor of microbial genomics at the University of Birmingham.
Peter Openshaw, professor of experimental medicine at Imperial College London, called the British government’s data on the new variant “of great concern,” noting that the “variant does seem about 40 to 70 percent more transmissible.”
He said the number of cases could double in “just six or seven days” at the current rate.
“So it is really vital that we get this under control,” he told science reporters on Saturday.
Joel Achenbach in Washington contributed to this report.