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New variants of SARS-CoV2 (the virus that causes COVID-19) have been in the news. You may have heard them called mutants, but this is a very inappropriate use of the term mutation. Viruses are always mutating. A mutation is simply a change in the sequence of nucleic acid building blocks. These building blocks are chemicals that act as letters in the words and sentences of molecular biology, just as the letters that you are reading on this page convey information based on how they are sequenced and punctuated. Different types of viruses differ in how quickly their sequences of genetic building blocks —known as genomes— undergo mutations, but all of them mutate. Often, a mutation has no consequences, which is why it is not correct to equate getting a mutation with the emergence of a problem. Other times, the consequences of a mutation can be beneficial, when a mutation in the genetic sequence of a virus makes the virus less lethal. In some cases, though, one or more mutations in a virus can have negative consequences, such as making the virus more transmissible, or possibly more lethal.
Whatever the change in the viral genome, the evolution of the virus depends on external factors. A virus is not alive in the sense of a bacterium, or a multicellular life form, because it cannot reproduce on its own; it must infect a living thing in order to reproduce by hijacking the cell’s protein assembling machinery. But a virus shares with true life forms the fact that it evolves according to selective pressure. When a mutation renders a virus better suited to reproduce, that mutation is passed on to the little baby virus particles that are created when a virus infects a host. In the case of a disease-causing virus like SARS-CoV2, this means that any mutations that make the virus more transmissible should be expected to thrive, resulting in variants of the virus that spread more easily between people. It does not mean that mutations causing increased lethality will thrive, however, since only spreading to more people, not killing more people, leads to more virus being produced. Indeed, often it helps a virus to evolve to be less lethal; that way they can spread to more hosts, like a common cold (many common colds are caused by coronaviruses, other than the more lethal coronaviruses that cause COVID-19, SARS, and MERS).
That’s how you need to think about the issue of variants of SARS-CoV2, along with the question of whether any new variant that is detected in human populations will be less vulnerable to the new vaccines, or the disease that the new variants cause will be less treatable with the therapies that are being used in those suffering from COVID-19 caused by older versions of SARS-CoV2. The news moves quickly, due to the high incidence of the virus in the human population and this can be stressful, particularly when you are pregnant and eager to know what your risk profile will be when you are admitted to the hospital to deliver. With these concepts in mind, let’s take a look at the three new variants of SARS-CoV2 that have been in the news.
The United Kingdom (UK) variant: Known officially as B.1.1.7, this variant, which was identified this past September is notable in that its genome contains a high number of mutations, changes in the sequence of genetic building blocks compared with the sequence of the “standard” SARS-CoV2 virus that we have come to know and hate over the past year. So you see that we are using the term “mutation” to refer to particular changes in the viral genome, whereas we are using the term “variant” to refer to the particular virus that is different from the more common form as a result of the various mutations within its genome. Compared with the more familiar SARS-CoV2, the UK variant spreads more quickly and more easily between people. On the other hand, researchers do not have evidence that this variant produces worse illness or worse mortality than the standard strain. It is potentially more deadly, only because it is more contagious. While the UK variant is more common in southeast England and London, where it was first identified, it has spread to various countries, including the United States. As of late January, 2021, the COVID-19 vaccines that are being administered (the Pfizer-BioNTech and Moderna mRNA vaccines) and that are on the verge of being administered (the AstraZeneca/Oxford and Johnson and Johnson DNA vaccines) appear to be just as, or nearly as, effective against the UK variant as they are against the standard strain of SARS-CoV2).
The South African variant: Known as variant 1.351, this variant has some mutations in common with the UK variant. It is of concern because, as of January 28, it has been identified in the United States, specifically in South Carolina. Additionally, researchers have found that the approved vaccines are slightly less effective in protecting against the South African strain, although Moderna has announced that its COVID-19 vaccine appears to be fairly effective and that it will be relatively easy to tweak the vaccine to cover this variant. That’s one of the beauties of the mRNA vaccine strategy; the sequence of building blocks for the genetic material can be adjusted quickly, although some amount of clinical testing would be needed regardless.
You also may have heard about the Brazilian variant. Known as the P.1 variant, it was identified in four travelers at an airport in Japan who had arrived from Brazil. As of the writing of this article in late January, 2021, it has not been reported in the US and we are awaiting news of how effective the vaccines are against it.
