A new strain of the SARS-CoV-2 coronavirus, technically called B.1.17, has spread rapidly in England since September, prompting several European countries yesterday to suspend flights with the United Kingdom.
This is what we know so far:
What is it?
It is a strain of the virus that has numerous genetic mutations compared to previously circulating strains. Most of these mutations focus on protein S, which the virus uses to bind to and infect cells in the human body. Some of these mutations have the potential to increase the contagiousness of the virus. Several of them had been previously identified in other strains of the virus. They had never been found together in the same strain.
When has it appeared?
The first samples of the B.1.1.7 strain of the coronavirus were identified on September 20 in the county of Kent, in the southeast of England, and on September 21 in the London metropolitan area. The fact that it was found in two patients independently suggests that the virus’s new variant had emerged a few weeks earlier.
The strain evolved in the body of a patient who was infected for weeks.
How did it appear?
The fact that many mutations coincide in the same strain suggests that it evolved in the body of a patient who was infected for weeks, which gave the virus enough time to adapt and accumulate genetic changes. The scientific team that has identified it proposes, as a hypothesis, that this could have occurred in an immunosuppressed patient.
Is it more virulent?
There is nothing to suggest that the new strain of the virus causes a more serious form of Covid than previous strains. An increase in hospitalizations or serious cases has not been detected in the areas of England most affected by the B.1.1.7 strain, beyond the increase due to the greater number of cases.
Is it more contagious?
Yes. According to a first estimate based on mathematical models, the new strain raises the virus’s reproduction R number by 0.4. This means that in Catalonia, where the R number is currently around 1.5, this figure would rise to 1.9 if the new strain were dominant at this time.
Why is it more worrying?
The control of the epidemic depends on the virus’s contagiousness and the opportunities given to it to spread. If contagiousness increases, to maintain the same level of control, it is necessary to reduce the opportunities you will have of causing infections. This means that it will be necessary to introduce stricter control measures to maintain the same control level. In Catalonia’s example, the measures introduced to control the second wave in mid-October, which included the total closure of the restoration, reduced the R number to around 0.7. If the new virus strain raises the R by 0.4, those measures would have been insufficient to control the second wave since they would not have reduced the R below 1.
Where has it come from?
The new strain has already spread to all of Great Britain, including Wales and Scotland within the UK. Its highest transmission occurs in the southeast of England, in the London region, responsible for 28% of Covid cases in early November and 62% in early December. It has already been detected outside the UK in Denmark, Iceland, the Netherlands, and Australia.
It is possible. In no country is the coronavirus genome of each patient sequenced to see which strain of SARS-CoV-2 they have exactly. Therefore, just because it was not detected does not mean that it has not arrived. British researchers who have identified the new strain indicate that it is imperative to “strengthen genomic surveillance on a global scale” to determine where the B.1.1.7 strain has already spread.
Will it affect the effectiveness of the vaccines?
Probably not, but it’s too early to tell. The vaccines stimulate immunity against the coronavirus protein S, which has the most mutations in the new viral strain. Since vaccines elicit a complex immune response that neutralizes protein S on several fronts, a small number of specific genetic mutations are unlikely to render them ineffective. Studies are already underway to assess the potential impact of the new strain on the efficacy of vaccines.