A transmission electron microscope image of SARS-CoV-2 virus particles emerging from the surface of cells cultured in the lab, with visible coronae. Image: NIAID-RML.
Scientists in the UK recently uploaded a preprint paper reporting a new strain of the novel coronavirus, dubbed B.1.1.7, that is 56% more contagious and genetically diverse from other known variants. Four days later, the British government announced the strain may in fact be up to 70% more contagious. What does this mean, and will it overthrow our vaccination efforts?
Most viruses, including SARS-CoV-2, mutate over time owing to a fundamental feature of their biology. Every time a viral particle replicates to make more copies of itself within a host, there’s a chance it might make a mistake and produce an inexact copy of its genetic material. This mistake is called a mutation.
The novel coronavirus’s general material is in the form of RNA, which in turn is a string of four compounds called nucleobases: adenine, uracil, guanine and cytosine. A mutation can be a deletion, insertion or a replacement of one nucleobase with another. Think of it like typos in a long piece of text – only that some mistakes make the words more meaningful while others weaken or garble the message.
In this context, B.1.1.7 corresponds to a mutation in the novel coronavirus’s RNA that renders the virus more contagious.
We can get a sense of the virus’s evolution by studying how its RNA has changed over time. Scientists are even able to profile these changes and determine if different variants arise together in a population, because of migration patterns, etc. And like with any scientific study, the amount and quality of data determines if the results are significant.
In the last few months, the UK has produced the highest number of gene sequences of the novel coronavirus. Why, just since December 1, the UK has produced sequences of viruses obtained from 3,700 people with COVID-19 – while the US, with a five-times larger population, has only 40 sequences.
The UK’s prodigious output means that as the novel coronavirus keeps mutating, there is a very good chance that important new mutations are going to be detected in this country first.
Second, the UK possessing a more thorough dataset implies that the B.1.1.7 variant might already be circulating in various other countries – with the only difference that those countries may not know that yet. The fact that the earliest sample in the UK’s dataset is from September makes this quite plausible: two months is enough time for the mutation to have arisen and spread in those places.
This said, it’s notable that the UK study is based on a mathematical model and hasn’t been confirmed in lab experiments, so its conclusions are more predictive than assertive.
The B.1.1.7 variant’s RNA differs from the oldest sequences by 23 mutations, with at least eight lying in the part of the RNA corresponding to the spike protein. Researchers also observed two deletions that scientists have previously reported, which appear to decrease human antibodies’ sensitivity to the virus. This is cause for concern – although we must also remember that the human body makes a myriad antibodies, and the combination varies from one individual to the next.
This in turn could be some comfort. The mRNA vaccine candidates for COVID-19, made by Pfizer/BioNTech and Moderna, are expected to be able to generate antibodies within the human body in sufficient form and quantity as to be effective against future infections. It is also notable that the novel coronavirus will need to mutate for many years before becoming able to completely overpower the vaccine as well as the human immune system.
In addition, a more contagious virus may not necessarily mean a more deadly virus. Contagiousness refers to how easily a virus can cause an infection in a body whereas deadliness refers to the infection’s severity. Like all other life-forms on Earth, viruses have an evolutionary motive to survive – which means it’s in their best interests to not kill their hosts too quickly. In these terms, there’s a good chance that B.1.1.7 is just another strategy for the novel coronavirus to prolong its existence.
And even as it figures out more ways to exist for longer periods, humans must continue to wait for further research and for governments to procure more vaccines – and continue masking and practice physical-distancing. In fact, these measures will always be able to protect us (to varying degrees) against different strains of the virus.
Shravanti Suresh is a graduate student pursuing a PhD in biochemistry at Iowa State University.