A version of the coronavirus known as D614G has hit headlines in recent days, after a Malaysian official said it was linked to two outbreaks and claimed it may affect vaccine development. This was followed by a disease expert claiming D614G may be more infectious but less deadly, potentially explaining falling COVID-19 fatality rates around the world.
Paul Tambyah, senior consultant at the National University of Singapore and president-elect of the International Society of Infectious Diseases told Reuters on Tuesday evidence suggests the proliferation of D614G in some parts of the world has been accompanied by a drop in death rates. This indicates it may be less deadly than other forms of the virus, he said.
“Maybe that’s a good thing to have a virus that is more infectious but less deadly,” said Tambyah.
He made the comment after the Malaysian director-general of health said the mutation had been linked to two outbreaks, Reuters reported. Noor Hisham Abdullah claimed D614G was ten times more infectious than other mutations, and vaccines under development may not be able to tackle it.
In the past few days, Google searches for D614G in the U.S. have spiked amid reports suggesting a “new strain” of the coronavirus had emerged.
But experts said D614G isn’t a new strain, but rather a mutation, and has previously been tied to outbreaks in Europe and the U.S.. It is also unlikely to affect vaccine development, and drops in deaths can’t be pinned to one factor alone.
What is the D614G mutation?
Mutations may sound alarming, but they are a normal part of the life-cycle of viruses. The germs are made up of genetic material, called RNA, encased in protein. When a virus infects a host, it make new copies of its genetic data so it can replicate. This process leads to small changes in the virus’ genetic information, called mutations.
According to Oscar MacLean, a bioinformatician at the Centre for Virus Research at the University of Glasgow, there have been more than 20,000 mutations to the coronavirus in the pandemic so far. D614G is the most well-known example,” he told Newsweek.
The D614G mutation affects one amino acid on the spike protein that the virus uses to invade our cells. He said it “almost always co-exists” with another mutation which affects how the virus replicates its genetic material.
D614G “has been the dominant form of SARS-CoV-2 in Europe and the USA for a while now,” he said.
Echoing MacLean, Dr Julian Tang, honorary associate professor in respiratory sciences at the University of Leicester, said in a statement “it is likely now the predominant SARS-CoV-2 genotype in most parts of the world now.”
MacLean previously told Newsweek caution must be taken before calling a mutation a new “strain”.
“By the definition of possessing unique mutations, we would have thousands of ‘strains’ of SARS-CoV-2 [the coronavirus], however these viruses are all expected to be functionally very similar, and so it’s somewhat meaningless to use this definition,” he said.
Is D614G more infectious?
Ian Jones, professor of virology at the U.K.’s University of Reading, told Newsweek: “That D614G continues to spread confirms that it has a Darwinian advantage in the virus world which is in keeping with the biochemical data which show that it appears to be a little more efficient [at] infecting cells in the lab. And generally viruses do tend to get more infectious and less pathogenic over time.”
At this stage in the pandemic, it seems “very likely” the combination of two mutation he previously described increases its ability to spread, said MacLean, adding: “however there’s uncertainty around how large this effect is.”
Is D614G less deadly?
MacLean described the link between D614G and lower death rates as “weak” and said rigorous analyses have failed to find any effect on mortality rates.
The combination of the amount of data coming out of the pandemic and the “constantly shifting situation” of the pandemic make it easy to compare things and find correlations “just by chance,” he said.
Jones said it is “very premature” to conclude from anecdotal reports that the virus is getting weaker in patients.
“Knowledge of how to treat patients also increases with time so there could be lots of reasons why the death rate falls, including that treatments are improving,” he said.
Paul Hunter, professor in medicine at The Norwich School of Medicine, University of East Anglia, said in a statement that while it is “certainly plausible” that D614G would become more infectious and less deadly, “it is not clear what real evidence is behind this statement or whether it is simply a suggestion.”
More research is needed to prove that the declining death rate is because of the new strain and not because of other factors, he said. These include that more young people are catching the virus than were in March, April and May; that doctors are becoming better at treating the virus; and because testing has expanded so people who are less sick are included in the numbers used to calculate the death rate, bringing it down.
Another factor that may be at play is that some of the most susceptible have died, leaving behind a “more robust human population” with a lower risk of dying.
It’s not possible to say the mutation causes a less severe disease without completing a comparative analysis with the parent strain, he said.
Will it affect vaccine development?
Tambyah and Sebastian Maurer–Stroh of Singapore’s agency for science, technology and research told Reuters it was unlikely the mutation would affect efforts to create a vaccine, as the changes in D614G aren’t to areas that the immune system typically recognizes.
Similarly, MacLean said: “the impact of D614G on current vaccines being developed is negligible.”
Tang said: “vaccines based on the previous form of the virus should still be effective – though further mutations may well occur by the time these vaccines are licensed for general use.”
Looking ahead, MacLean said: “it will be important to continue to monitor for mutations which might provide immunity evasion over the coming years, but there’s no evidence for that in any mutations observed at notable frequencies so far, and not for D614G in particular.”