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article imageEssential Science: Is SARS-CoV-2 becoming more infectious?

By Tim Sandle     Jul 13, 2020 in Science
Is the novel coronavirus mutating? The answer is yes, all viruses mutate. Is this of significance? The answer here is dividing scientific opinion. One new finding relating to a spike protein could raise concerns.
The issue concerns a newer variant of SARS-CoV-2 where a reported D614G change in the outer spike of the virus (the protruding that give the name ‘corona’). This variant appears to be out-competing the original strain. However, there is no evidence as yet that this alteration makes patients more ill.
The coronavirus has hit business in Japan hard
The coronavirus has hit business in Japan hard
The research comes from the Los Alamos National Laboratory, and it shows that an identified change in the SARS-CoV-2 coronavirus virus genome, which was earlier linked with increased viral transmission and the spread of COVID-19, has been shown to be more infectious in cell culture. The activity in cell culture, however, does not necessarily mean that the same elevated infectivity will occur in people.
Readers need not be too alarmed about the term ‘mutation’. All viruses mutate, especially RNA viruses (of the SARS-CoV-2 type). Mutations occur due to activities within the virus, such as replication enzymes. Such enzymes can create mistakes or ‘mutations’) when copying genetic material. A mutation is not necessarily more infectious or easier to contract.
New variant
The presence of the D614G variant was detected in April 2020, and several instances suggested a different, repetitive pattern. In then came to light that, globally, the D614G variant was appearing to surpass the original form and characteristic variant of SARS-CoV-2.
The new strain of coronavirus has so far killed 17 people
The new strain of coronavirus has so far killed 17 people
By harnessing geographic information from samples and using samples of the viruses deposited in the GISAID COVID-19 viral sequence database, this allowed scientists to look for instances of the recurrent pattern. The GISAID database contains tens of thousands of viral sequences, plus genetic sequence and related clinical and epidemiological data associated with human viruses, and geographical as well as species-specific data.
It was found that a shift in the viral population from the original form to the D614G variant was taking place around the world, in every country, county, and city.
What is of interest is parallel research that indicates how this D614G change increases the virus's infectivity, at least within the laboratory. However, it remains that additional studies are needed in order to determine the full implications of the change.
While the mutation has occurred, it stands that the SARS-CoV-2 virus has a low mutation rate overall (compared with those viruses which cause influenza and HIV). The origin of the D614G variant appears relates to four linked mutations that moved together around the world, appearing as a consistent set of viral variations.
Patient risk
The new variant has been coded ‘G’. The overall descriptor - D614G - refers to a change in the amino acid (from D to G) in position 614 on the viral genome. An alternative term for the virus is the G614 variant.
In terms of an additional risk to people, there is no evidence that the virus leads to worse symptoms. It may be, however, that the variant is easier to contract (in terms of being more readily transmitted). From patient samples, there are higher viral loads of the G variant isolated from within the upper respiratory tract.
Going forwards
The observed mutation may also offer clues as to the origins of the viruses and the way that it may alter in the future, this remains an important area of applied coronavirus research.
People walk past a graffito reading: "Covid(19) knows no borders  be like Covid" in Berlin
People walk past a graffito reading: "Covid(19) knows no borders, be like Covid" in Berlin
Research paper
The research has been published in the journal Cell. The research paper is titled “Tracking changes in SARS-CoV-2 Spike: evidence that D614G increases infectivity of the COVID-19 virus.”
Essential Science
This article forms part of Digital Journal’s long running Essential Science column, where a topical science subject is examined each week.
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