A mutation may have made COVID-19 more contagious
Written by James Kingsland on November 6, 2020 — Fact checked by Alexandra Sanfins, Ph.D.
Between March and July 2020, a particular mutation became almost ubiquitous in SARS-CoV-2 infections in Houston, TX. This strongly suggests that it makes the virus more infectious. However, there is no evidence to suggest that it makes the virus any more deadly.
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Metropolitan Houston reported its first case of COVID-19, which is the illness that develops due to SARS-CoV-2, on March 5, 2020. A week later, the virus was spreading within the community.
A previous study found that strains of the virus containing a particular mutation, called G614, caused 71% of cases in Houston in the early phase of this first wave of infections.
A follow-up study by the same team now reveals that by summer, during the second wave, this variant accounted for 99.9% of all COVID-19 infections in the area.
The new research, which a team from the Houston Methodist Hospital in Texas led, now appears in the journal mBio.
The mutation, which has spread worldwide, results in the substitution of one amino acid for another at a particular position in the virus’s spike protein.
Amino acids are the building blocks of proteins. They are assembled in a particular sequence depending on the genetic blueprint of the virus.
The mutation replaced an amino acid called aspartate with another called glycine in the spikes, which allows the virus to break into its host cells. The substitution appears to make it easier for the virus to invade the cells.
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A study from earlier this year showed that viruses carrying this mutation are more infectious in cell cultures growing in the laboratory.
The same team found clinical evidence to suggest that people with this variant had more virus particles in their upper respiratory tracts than people with other variants. That said, despite this extra “viral load,” their illness appeared to be no more severe.
Another analysis of more than 25,000 viral sequences in the U.K. suggests that viruses with this mutation transmitted slightly faster and caused larger clusters of infections.
The latest study sequenced the genomes of 5,085 strains of the virus from the two COVID-19 waves in Houston.
At the time of diagnosis, people with the G614 variant had significantly more virus particles in their noses and throats, possibly as a result of its increased infectivity. However, there was no evidence to suggest that these people experienced more severe disease as a result.