Media are reporting on a pre-print journal article (yet to be peer-reviewed) which proposes the existence of a potentially more transmissible (“contagious”) strain of the SARS-CoV-2 virus, due to a mutation to the spike region called ‘D614G’.
Two-thirds of the sequenced strains (or “isolates”) globally and half of the sequences in some countries (such as Australia and India) now have this D614G mutation , which is apparently increasing its representation among newer strains.
Does the D614G strain cause more severe disease?
Professor Seshadri Vasan, head of CSIRO’s Dangerous Pathogens Team testing COVID-19 vaccine candidates at the Australian Centre for Disease Preparedness in Geelong, said:
“Even if a particular strain may be more transmissible, it does not mean it will cause a more severe form of disease. In fact, the authors of this pre-print have themselves said ‘there was no significant correlation found between D614G status and hospitalisation status’.
“This virus is still adapting to its new human host. It is expected that, over time, different dominant strains will appear in different parts of the world. This is especially true where movement around the world is restricted.
“This should not cause undue alarm. While it is normal and anticipated for RNA viruses to mutate, the SARS-CoV-2 virus has a ‘proof-reading’ mechanism which limits the rate at which it can mutate.
“More research is required before we can separate out host and environmental factors to draw firm conclusions from this limited data.”
Will this mutation affect the vaccines or diagnostics being developed?
Professor Seshadri Vasan, CSIRO Dangerous Pathogens Team Leader, said:
“Based on what we know at this point, we do not believe that this poses serious concerns about vaccine development, unlike what we see in seasonal influenza where we need to tweak the vaccine each year for Northern and Southern Hemispheres. However, many vaccines for COVID-19 target the spike region so we will keep a close watch on this and other mutations.”
“CSIRO is planning experiments to confirm whether the D614G mutation will impact antibody responses to the CEPI-funded vaccines (Oxford and Inovio) under evaluation at CSIRO’s Australian Centre for Disease Preparedness.”
“CSIRO will continue to monitor the national and global situation regarding the genetic evolution of SARS CoV-2, as it is inevitable that other mutations will be identified and reported.”
Is this strain circulating in Australia?
Associate Professor Denis Bauer, Transformational Bioinformatics Team Leader at CSIRO’s Australian e-Health Research Centre, said:
“We have been monitoring whether Australia will be affected by the D614G change in the spike protein caused by a single base mutation A to G at location 23403.
“In Australia it currently seems to be less frequent than the world average, appearing in only 50 per cent of the surveyed sequences (in 717 high quality isolates out of the total 1300 Australian isolates, 3rd May).
“This mutation is present in roughly two third of all global strains but only represents half of all Australian strains. NSW and QLD show the lowest rate of the mutation (representing one-thirds of all strains) while VIC and WA more closely resemble the international distribution. NT is split down the middle, while there was no data for Tasmania or South Australia.”
“However, this ratio might change in the future as the D614G strain is only one of currently 10 strains circulating, with no clear evidence on clinical outcomes for any strain so far. Mutations are a normal part of a virus’ evolution and do not necessarily have an impact on the severity of disease.”