The N501Y mutation of the SARS-CoV-2 coronavirus was identified in mid-December in the United Kingdom. According to the British Prime Minister, it could be "up to 70% more contagious than the previous strain". Scientists call for caution.

London and the south-east of England will be spending the end of year celebrations under wraps. On Saturday December 19, British Prime Minister Boris Johnson decided to reconfigure part of the country, less than two weeks after the partial deconfinement of December 3. The UK faces an upsurge in the number of new Covid-19 cases.

The resumption of the epidemic would be fueled by "a new variant of the coronavirus" which "seems to spread more easily and could be up to 70% more contagious than the previous strain", indicated the head of the British government during a press conference.

Residents are instructed to stay at home, non-essential businesses are closed, and travel (to travel abroad or within UK) has been banned since December 20.

A strain identified in mid-December in the United Kingdom 

 The circulation of the N501Y strain of SARS-CoV-2 in the United Kingdom was revealed on Monday December 14 by the British Minister of Health, Matt Hancock. This mutation, which appeared in mid-September, in London, or in Kent, is on the way to becoming the "dominant" strain in the south of England. According to Patrick Vallance, scientific adviser to the British government, it would be the cause of 62% of the contaminations recorded in December in London and 43% of the contaminations recorded in the south-east (against 28% in mid-November). 

"N501Y was already circulating sporadically much earlier this year outside the United Kingdom, in Australia in June-July, in the United States in July and in Brazil in April", however noted Dr Julian Tang (University of Leicester), interviewed by AFP. It has been spotted by the British COG-UK consortium which is studying the coronavirus genome among positive test samples to identify its variants and their geographic distribution.

 Outside British territory, the World Health Organization lists nine cases in Denmark, one case in the Netherlands and one in Australia. In France, no case has yet been reported. "Across Europe, where transmission is high and widespread, countries must strengthen their control and prevention procedures," the UN organization said in a statement.

 Why and how has the SARS-CoV-2 coronavirus mutated?

  Coronaviruses mutate regularly: "after having infected our cells, they multiply by making copies of themselves. This process is not perfect and the copies can contain errors: the famous mutations [...] However, like other coronaviruses, SARS-CoV-2 is rather stable because it has an enzyme that corrects these errors (an exoribonuclease) ", indicates Inserm on its website. 

According to Patrick Vallance, the new variant of SARS-CoV-2 differs from the "model" virus in 17 points, an "unusually high" number. Most would be "associated with changes in the protein that the virus makes" and "the way the virus binds to or enters cells," he said. The main fear to date is that the disease will spread more quickly.

Note: several dozen SARS-CoV-2 mutations have been identified since the start of the Covid-19 pandemic, without alarming consequences.

Is the new variant of SARS-CoV-2 more dangerous?

  Scientists do not yet have sufficient data to know whether the N501Y mutation induces more serious or more contagious forms of Covid-19. On Saturday 19 December, the British Prime Minister also indicated that it was too early to measure the impact of this discovery on the effectiveness of vaccines.  

An article published in the British Medical Journal on Wednesday indicates that there is currently no way to establish a causal link between the increase in Covid-19 cases and the circulation of the N501Y strain. Containment is necessary as a precaution, but we cannot know whether the number of new contaminations has increased again due to the release of the population, or because of a potentially more contagious strain.  

 For its part, the World Health Organization (WHO) does not recognize "any evidence of a change in the severity of the disease" at this stage. In view of "preliminary" information, however, she is concerned that the UK variant may "affect the effectiveness of certain diagnostic methods". Asked by CNN, England's chief medical officer, Chris Witty, says work has been launched "urgently" to determine whether the mutation of the virus may or may not lead to a higher death rate, or whether it affects the effectiveness of treatments and vaccines.