Researchers are trying to determine whether the variant will cause more-serious disease and evade vaccines

LONDONBritish public-health officials were mystified. Nationwide restrictions were driving down the spread of coronavirus across much of the country by late November. But in one part of southeast England infections were inexplicably surging.Epidemiologists set out to investigate, at first assuming there had been some kind of superspreader event or that people were ignoring social-distancing rules at work, in illegal house parties, or elsewhere. They found nothing. Stumped, they turned to a team of scientists monitoring mutations in the virus genome.On Dec. 8, the group, known as the Covid-19 Genomics UK Consortium, found a new variant of the virus, with 23 mutations, in a sample taken from a patient in Kent, near the center of the outbreak in late September. They found the same variant in someone tested in London a day later.
Some of the new mutations had the potential to increase the transmissibility of the virus.
The coming together of the genome data and details of an outbreak in Kent led to the key connection, said
Sharon Peacock,
the University of Cambridge microbiologist who leads the genomics team. She said in an email that it was the scientists light bulb moment.
The U.K. increased restrictions after announcing a new variant of the coronavirus that appears to be more transmissible.
Two-week percentage change in new daily confirmed Covid-19 cases
Note: Luxembourg change calculated using data for Dec.10; Spain from Dec. 9.
Source: Johns Hopkins CSSE
New information continued to flow in and the British government first raised its concerns about the variant publicly on Dec. 14, when Health Secretary
Matt Hancock
told British lawmakers it had been responsible for 1,000 cases in London and southeast England and was spreading.
Initial analysis suggests this variant is growing faster than the existing variants, Mr. Hancock said.
Meanwhile, scientists were digging more deeply into the nature of the new variants mutations.
Viruses mutate all the timethough coronaviruses more slowly than some other common viruses like influenza. What stood out in the new variant was that a larger-than-usual number of mutations affected the code for the amino acids that produce the proteins that make the virus.
One mutation alters the viruss spike protein in a way that has been known to make it easier for the virus to stick onto cell walls and enter the body. Along with two other mutations, the change has the potential to give the variant a possible advantage over previous versions in infecting people.
It was a variant that hadnt been seen beforeand the number and nature of its mutations was, scientists say, unprecedented.
Its kind of out on a branch, its really quite striking actually that its so different from everything else around it in the U.K., Dr. Peacock said.
At the time of the discovery of the new variant, it was accounting for 62% of all cases recorded in London. And infections have continued to rise rapidly.
The latest data show the seven-day average of cases in the week to Wednesday across the U.K. was up 61% over the previous week, even as case counts fall in most of the rest of Europe. Hospitalizations and deathslagging indicators of the viruss spreadwere up 16% and 20%, respectively.
The underlying mechanism driving the rapid spread is not fully clearit could be because the virus replicates faster, which means you get higher viral loads which means you are more infectious,
Peter Horby,
chairman of the New Emerging Respiratory Virus Threats Advisory Group advising the British government, told lawmakers on Wednesday.
Another hypothesis is it could be that it takes a shorter time between being exposed and being infectious, which would lead to quicker transmission. Or it could mean the duration of infectiousness is longer, Dr. Horby said.
Researchers are now working to answer two crucial questions: Will the new variant cause more-serious disease and will it be able to evade vaccines?
British scientists say they dont have enough evidence at the moment to answer either definitively but are working hard to find out.
On the vaccine, they are testing blood samples from people who have had the vaccine against the new variant to see if they show a different response compared with that elicited by the previous version.
Footage shows empty supermarket shelves while trucks bearing cargo get stuck at the border after France imposed a travel ban on Britain following the spread of a new coronavirus strain. Other countries have also barred passengers from the U.K. Photo: Neil Hall/EPA/Shutterstock
The widespread view among scientists and the developers of the
Pfizer Inc.

SE vaccine, is that the vaccine produces antibodies that attack a number of different sites on the virus so it is unlikely that the changes in a small area will neuter the vaccines potency.
On the severity of the disease caused by the new variant, they are waiting for hospitalization and death data, which lag case counts, to tell them more.
As they have delved into the new variant, British researchers have spent recent weeks quietly hunting for patient zero. They have sifted through the contacts of the two people who were the first identified with the variant, neither of whom was ill, and others who were infected early.
One hypothesis is that the variant arose in a person with a compromised immune system. People with deficient immune systems are often the host when viruses undergo a large number of mutations because the virus is able to survive in their system for so long.
In an ideal situation you would know who the index case was, said Dr. Peacock. We dont know at all, if this has arisen in a patient in the U.K. or if it has been introduced, we categorically cant tell at the moment.
In the week after the new variant was made public, new data and epidemiological modeling made British scientists increasingly convinced that the new variant reproduced faster than its predecessors. Some models suggested it was 50% to 70% more transmissible than other versions.
By Dec. 18, as new infections in the region continued to accelerate, a meeting between government officials and scientists alarmed the government, prompting a significant shift in policy.
On the following day, Prime Minister
Boris Johnson
announced new lockdowns for regions where the virus was spreading rapidly and cut a planned five-day Christmas relaxation of restrictions to just one day in the rest of the country.
Write to Joanna Sugden at and Stephen Fidler at
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