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The UK variant may increase mortality rates

The UK variant of SARS-CoV-2 was discovered in the United Kingdom in September 2020. It carries numerous mutations, notably in the spike (S) surface protein, and seems much more infectious than other variants. Initial studies did not indicate changes in the illness’ severity. However, researchers at the London School of Hygiene and Tropical Medicine have evaluated the impact of the UK variant on mortality rates, and have shown that it is linked to rises in severe cases of COVID-19.

`The researchers studied more than 2 million positive cases of SARS-CoV-2 between the 1st of November 2020 and the 14th of February 2021 in the United Kingdom and estimated the number of individuals infected with the UK variant. The loss of 2 amino acids in the spike of the UK variant makes it possible to spot this variant through PCR tests. It is possible to estimate the number of individuals infected by the variant, and there is a clear increase in the second wave (94% of cases after the 24th of January 2021) as compared to the first wave (6% before the 24th of January 2021).

This can be represented as follows:

How many of these were serious cases? 19 615 people infected died, which is 0.87% of the 2 245 263 individuals studied. But if we consider only deaths occurring during the 28 days following the first positive COVID-19 (the standard UK measure), then the rate of mortality is 1,86% for people infected with the UK variant, and 1,42% for the others. The researchers used statistical models  to show that the risk of death in the 28 days following a positive test could be 55% higher for people infected by the UK variant after adjustment for different criteria (age, sex, ethnic origin, etc.). However the risk of dying from COVID-19 remains less than 1% in individuals younger than 70.

So the UK variant of SARS-CoV-2 is not only more infectious, but it is also more deadly. Even though a larger viral charge has been observed in patients infected by this variant, the mechanism causing increases in mortality has not been identified. More research will be necessary to be able to answer this question.

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