- In September 2020, scientists identified a more contagious variant of SARS-CoV-2, the virus that causes COVID-19, in southern England.
- An analysis now suggests that the risk of dying for people who contract the new variant is around 35% higher compared with those who acquired preexisting variants.
- Other researchers caution that the results are preliminary and that the new variant may simply be passing on to a greater number of vulnerable people.
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In the United Kingdom, there have been more COVID-19 deaths per 100,000 population than in any other country. The U.K. also has the highest daily mortality rate in the world.
One of many factors contributing to the country’s exceptionally high death rate may be the emergence of a new, more contagious variant of the virus, first identified in September 2020 in Kent, southeast England.
The variant, officially known as B.1.1.7, has become the dominant variant of the virus in the U.K. and has spread to many other countries.
Several studies have found B.1.1.7 to be more transmissible than older variants of SARS-CoV-2. However, scientists remain unsure whether it causes more severe disease.
An unpublished analysis by epidemiologists at the London School of Hygiene and Tropical Medicine now suggests that, regardless of age, gender, or ethnicity, B.1.1.7 is more likely to cause death than preexisting variants.
Overall, the analysis by lead researcher Dr. Nicholas Davies and his colleagues found that people in the community with a suspected B.1.1.7 infection are 35% more likely to die compared with those who had an older variant.
In absolute terms, this would mean that for males aged 70–84 years with a SARS-CoV-2 infection, their risk of dying from the illness within 28 days increases from 4.7% for infections with an older variant to more than 6% for B.1.1.7.
For males aged 85 or older with COVID-19, their risk of dying increases from about 17% to nearly 22% with the new variant.
The study, which has not yet gone through the peer-review process, has been uploaded to the MedRxiv preprint server.
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To gauge mortality rates for the new variant, the team investigated the outcomes of 858,181 people who tested positive for the virus in the community between November 1, 2020 and January 11, 2021.
By chance, the scientists were able to determine which of these individuals had B.1.1.7 thanks to a glitch in the standard, lab-based polymerase chain reaction (PCR) test for the virus.
The test identifies the virus by amplifying the sequences of three of its genes. But the new variant has a mutation in one of these three — a gene that encodes its spike proteins.
This means the PCR test can amplify only two out of the three genes in B.1.1.7, which allowed the researchers to deduce who had contracted this variant.
They found that out of all the positive tests over this period, 48% appeared to be the new variant.
In total, 2,091 of the patients died within 28 days of their first positive test.
After adjusting the figures to account for other factors that could increase the severity of illness, including age, sex, and ethnicity, the mortality rate appeared to be 35% higher among those who have the new variant.
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The study focused exclusively on patients who tested positive for the virus in the community. It covered only 7% of COVID-19 deaths in England, while the effect could therefore disappear if people who tested positive in hospitals are included, according to Dr. Muge Cevik, a public health researcher at the University of St Andrews.
Preliminary work by other groups has not found an increased risk of death in people admitted to hospitals with the new variant.
The possibility also remains that because B.1.1.7 is more contagious, it is more likely to overwhelm limited hospital resources and therefore reduce the quality of care than older variants.
However, Dr. Davies told Nature that his team ruled out this possibility by comparing the mortality rates associated with the new and older variants for people who received a test at the same time and geographical location.
The idea is that, overall, the quality of care provided by a local hospital at a particular point in time should be the same.
The researchers speculate that people with B.1.1.7 may develop higher concentrations of the virus, or “viral loads,” in their bodies compared with older variants.
This may lead to more severe disease and reduce the effectiveness of standard hospital treatments.
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