Concept of COVID-19 or 2019-ncov coronavirus
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U.K. authorities are scrambling to contain a new mutated variant of the coronavirus that appears to be spreading rapidly. As yet, scientists don't know much about the new strain, but the fact that it appears to increase in prevalence rapidly even during lockdown is causing serious concern among the British government.

Prime Minister Boris Johnson ordered new tier 4 restrictions for large swaths of the country on Saturday, effectively canceling Christmas get-togethers for millions — just days after he said such restrictions would be "inhuman." That was followed on Sunday by a slew of travel bans on people coming from the U.K. by countries across Europe and beyond.

'Mutant strain' sounds scary. Is it?

Not in itself. The viral genetic material undergoes random changes all the time, though mutations are relatively sluggish in the coronavirus that causes COVID-19 (known scientifically as SARS-CoV-2). Many of these changes make little or no difference to the way the virus behaves. Others may make it more or less infectious or more or less deadly. But the two properties do not necessarily go together.

Is the new variant the first to emerge?

No and it certainly won't be the last. One example is the so-called D614G variant with a mutation to part of the virus's spike protein, which it uses to break into human cells. After appearing in January, by the summer it was found in almost all samples of the coronavirus worldwide. That appears to be because it is better at infecting cells and replicates in greater numbers.

Where is the new strain spreading?

Last Monday, the U.K.'s Health Secretary Matt Hancock announced in parliament that the new variant was spreading in the South East of England and at least 60 local authorities had identified cases caused by it. Maria Van Kerkhove from the WHO told the BBC's Andrew Marr program that the new variant had been detected in Denmark and the Netherlands, as well as a case in Australia. Other cases have been found in Belgium and Italy, according to the European Centre for Disease Prevention and Control.

Is it more infectious?

After initial caution last week, scientists are becoming more convinced that the VUI-202012/01 variant of coronavirus is more transmissible. On Monday, experts from the the U.K.’s New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG) told journalists that the group now has "high confidence" that the strain has a transmission advantage compared with other variants. This compares with the "moderate confidence" that the committee said it had in a meeting on Dec. 18.   

That might seem obvious given how quickly the strain appears to be spreading, but it can be hard to exclude other explanations such as a super-spreader event giving the variant a boost — particularly since scientists don't know what might be making the viral strain more infectious. However, scientists from NERVTAG said that looking at the genetic data of the virus alongside the epidemiological situation had convinced them of its higher rate of transmission. They noted that the strain was able to keep spreading during the November lockdown in England, even while rates of infections for non-variant coronavirus fell. 

NERVTAG member Wendy Barclay, the head of the department of infectious disease and Action Medical Research Chair Virology at Imperial College London, said the variant coronavirus had an unusual cluster of mutations with 22 coding changes. A number of these affect the virus's spike protein and could help explain its higher reproduction rate. "We don’t understand the biology of all the changes, but adding them all up together there’s a feasible explanation for why this could be more transmissible," Barclay said.

How much faster is it spreading?

The new strain "has demonstrated exponential growth during a period when national lockdown measures were in place," the NERVTAG meeting notes state. The scientists estimate that the growth rate of the virus is 71 percent higher than other variants of the virus. That is boosting the R-value by between 0.39 and 0.93. That is very likely to push the R-value over 1, meaning that the epidemic grows rather than shrinks. One note of caution though: The mutant strain of the virus is hard to DNA sequence so this may be an underestimate.

It it more deadly?

“There is currently nothing to suggest that this variant is more likely to cause serious disease and the latest clinical advice is that it is highly unlikely that this mutation would fail to respond to a vaccine,” Hancock told MPs last week.

The NERVTAG scientists say there is currently insufficient data to say what the mechanism of increased transmissibility is or whether the variant is more deadly. So far, four deaths in around 1,000 cases have been identified. As yet, there is also not enough data to draw definitive conclusions on the age profile of people infected and whether the mutated virus is recognized by the immune system of someone who has already had the virus — or indeed has been vaccinated. Worryingly though they state: "Four probable reinfections have been identified amongst 915 subjects with this variant."

How are other countries reacting?

Several countries in Europe and around the world have introduced temporary bans on travel from the U.K. in an attempt to avoid importing the new viral strain including France, Germany and Belgium. More detail here.

More from ... James Randerson and Carlo Martuscelli