Why the U.K. Coronavirus Strain Just Got (Slightly) Deadlier, To Our Surprise
Wasn’t SARS-CoV-2 supposed to become less deadly as it evolves? After all, a dead host is a dead-end for viruses.
Author’s note: A few clarifications have been added at the end of this article.
About a week post-publication, about 250 news outlets have covered the new study showing that people infected with the B.1.1.7 coronavirus (SARS-CoV-2) strain — first discovered in the U.K. around Sept 2020 and has now spread to over 90 countries — are 64% more likely to die than those infected with prior strains or variants.
This probably comes as a surprise since many of us thought that SARS-CoV-2 would become milder over time. After all, as viruses couldn’t live without a host, a dead host is a dead-end for viruses. So, what’s the point of killing the host quicker? This article will explain why this assumption is not necessarily true and why SARS-CoV-2 just got deadlier.
Although there’s debate on the term usage between strains and variants, this article defines a strain as a viral variant that has evolved a different biological property.
The new study that confirms what we don’t want
The study, “Risk of mortality in patients infected with SARS-CoV-2 variant of concern 202012/1: matched cohort study,” published in the British Medical Journal (BMJ), is authored by researchers in renowned institutions in the U.K.
The study used PCR to differentiate between strains by the S (spike protein) gene. If the PCR detected other SARS-CoV-2 genes — such as the N or ORF1ab genes — except the S gene, it means that the person has been exposed to the B.1.1.7 strain whose spike protein is distinct from the older strains. Likewise, if the PCR detected the S gene, it means that it’s the prior SARS-CoV-2 strain with the older spike protein. A cycle threshold (Ct) value of <30 is considered as a positive result, a reasonable number.
The study then matched 54,906 persons with positive S gene (older strain) with 54,906 persons with negative S gene (B.1.1.7 strain) — ensuring that age, sex, ethnicity, income, and geographical distribution are…