All viruses mutate and SARS-CoV-2 is no exception. There have been over 4,000 mutations recorded to date, almost all are inconsequential. The English mutation, however, is of great clinical significance.
Although only making headlines towards the end of December 2020, the new coronavirus strain appears to have been around since November, especially in the southeast of England and within the London area. The point of origin, or at least where the first case was detected, appears to be the county of Kent. Within a few weeks the virus is responsible for around 60 percent of all recent infections in these impacted areas. This is the VOC 202012/01 variant. Here ‘VOC’ represents ‘Variant of Concern’ and the numbers indicate the date – December 2020.
The variant has arisen through a mutation. Specifically there is a mutation in the receptor binding domain of the spike protein. This occurs at position 501. The mutation is the product of where the amino acid asparagine has been replaced with tyrosine. For this reason, the mutation is coded N501Y. The variant has several other mutations, although the position 501 mutation is the most clinically significant. The mutation affects the part of the virus that connects to the ACE2 cells that line the human lung, and of which are the primary route of infection.
It is uncertain why the new variant has emerged. One possibility is that the virus is that the mutation is a logical adaptation to become a better fit to spread in humans. What is of interest, and consequentially concern, to scientists is the pace at which the rare strain has become a common strain.
By being more infectious, this is a product of increased viral load, tissue distribution of virus replication, and serial interval. Other factors include the age profile of the cases and the overall disease severity. Current estimates put the increased severity at 70 percent compared with the original strain. This promoted the UK government to impose severe restrictions across the four nations.
The two main mechanisms of infection remain airborne, in the form of larger droplets, which can fall out of the air rapidly within seconds to minutes; and with smaller droplets and particles. The droplets can remain suspended for many minutes to hours and travel large distances, depending on the direction and velocity of air currents. Importantly the preventative measure to avoid infection remain the same: Physical distancing, hand washing, surface disinfection, and mask wearing.
The important questions that scientists need to grapple with are understanding how easily the new strain of virus is transmitted (and why it is easier to transmit than the original strain) and assessing whether the newly approved vaccines will protect people against the strain. This requires deciphering the virologic, epidemiologic, and clinical characteristics of the virus.
In related news, a South African variant has been detected and this also has the N501Y mutation. Of interest, and concern, is the fact that this variant emerged completely independently of the UK strain and it is not related to it.
