Viruses are the fashionistas of the microbe world. They change their appearance constantly but such changes are usually small, transient and of little practical significance for how they spread or how deadly they are. SARS-CoV-2, the covid-19 virus, has so far been no exception. But a new variant of it that is spreading rapidly in Britain appears to buck the trend. According to researchers advising the British government, it may be 40-70% more transmissible than the other variants in circulation. Britain has alerted the World Health Organisation about this variant, provisionally called VUI 202012/01 (short for the first “variant under investigation” in December 2020).
The authorities are rushing to limit its spread. Swathes of Britain where VUI 202012/01 is most prevalent, including London, went into lockdown in the early hours of December 20th. By the evening, Belgium, France, Germany, the Netherlands and Italy had banned flights from Britain. Other countries are sure to follow suit. The port of Dover was closed to outbound lorries and ferry passengers after France closed its border for 48 hours on the evening of the 20th.
VUI 202012/01 was first found in Britain in September. By mid-December, genomic sequencing had detected more than 1,500
infections involving it in the country (about 10% of those in Britain who test positive have their viruses so sequenced). A few cases of the variant have been reported by Belgium, Denmark and the Netherlands. But most European countries sequence a much smaller proportion of their samples than Britain does, so more widespread circulation of this variant outside Britain cannot be ruled out, says Pasi Penttinen of the European Centre for Disease Prevention and Control.
It is not yet clear whether VUI 202012/01 causes symptoms that are different or of different severity from those induced by its cousins. Studies to answer that question are under way in Britain. Researchers are also looking for additional evidence that this variant is more contagious-and what biological mechanisms may be at play. Two factors suggest greater contagiousness. First, it has spread much faster than other variants in parts of Britain where infections have been rising unusually rapidly. It accounted for 62% of new infections in London in the week ending December 9th, up from 28% in early November. The second red flag is the particular combination of mutations and other tweaks in its genome-23, which experts say is an unusually large number given how the virus has changed so far. More worrying, laboratory and animal studies have found that several of these changes make the virus better at infecting cells, at making more copies of itself once it enters those cells, and at evading antibodies made by the immune system during infection with other variants.
Several of the changes in VUI 202012/01 are in “spike”, a protein found on its surface, and which it uses to enter cells. Spike protein is the target of the first covid-19 vaccines. But these vaccines stimulate immune reaction to parts of the protein not affected by those mutations. And if further mutations should change that state of affairs, then some of the vaccines are of a type that is much easier to adjust to get around the problem than are conventional medicines.
The big worry for now is whether VUI 202012/01 is, indeed, a lot more contagious than other variants. If the current estimates from Britain’s preliminary data are confirmed, it can increase by 0.4 or more the virus’s reproductive number (known as R), which is the average number of people who catch the virus from an infected individual. This will mean that far stricter measures would be needed to slow down the spread of covid-19 wherever this variant lands. The urgent attempts to contain its spread are therefore warranted. How much it can be slowed down until vaccines start to make a difference is an open question.
Source: The Economist
