Mutant coronavirus in the United Kingdom sets off alarms

On 8 December, during a regular Tuesday meeting about the spread of the pandemic coronavirus in the United Kingdom, scientists and public health experts saw a diagram that made them sit up straight. Kent, in the southeast of England, was experiencing a surge in cases, and a phylogenetic tree showing viral sequences from the county looked very strange, says Nick Loman, a microbial genomicist at the University of Birmingham. Not only were half the cases caused by one specific variant of SARS-CoV-2, but that variant was sitting on a branch of the tree that literally stuck out from the rest of the data. “I’ve not seen a part of the tree that looks like this before,” Loman says.

Less than two weeks later, that variant is causing mayhem in the United Kingdom and elsewhere in Europe. UK prime minister Boris Johnson announced stricter lockdown measures, saying the strain, which goes by the name B.1.1.7, appears to be better at spreading between people. The news led many Londoners to leave the city, before the new rules take effect, causing overcrowded railway stations. Also the Netherlands, Belgium, and Italy announced they were temporarily halting passenger flights from the United Kingdom.

Scientists, meanwhile, are hard at work trying to figure out whether B.1.1.7 is really more adept at human-to-human transmission—not everyone is convinced yet—and if so, why. They’re also wondering how it evolved so fast. B.1.1.7 has acquired 17 mutations all at once, a feat never seen before. “There’s now a frantic push to try and characterize some of these mutations in the lab,” says Andrew Rambaut, a molecular evolutionary biologist at the University of Edinburgh.

Researchers have watched SARS-CoV-2 evolve in real time more closely than any other virus in history. So far, it has accumulated mutations at a rate of about 1 to 2 changes per month. That means many of the genomes sequenced today differ at around 20 points from the earliest genomes sequenced in China in January, but many variants with fewer changes are also circulating. “Because we have very dense surveillance of genomes, you can almost see every step,” Loman says.

But scientists have never seen the virus acquire more than a dozen mutations seemingly at once. They think it happened during a long infection of a single patient that allowed SARS-CoV-2 to go through an extended period of fast evolution, with multiple variants competing for advantage. (Source:

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