An early mutation may have helped the coronavirus spread more rapidly

Back in May, a pre-print study (meaning not peer reviewed) suggested that a mutated strain of the coronavirus may be spreading more quickly than the original strain. But as I noted at the time, several virologists were quick to cast doubt on those conclusions, noting that you couldn’t rule out the possibility that the more common variant had simply gotten “lucky” in the sense that Italy hadn’t done as good a job as China in cracking down on the virus.

Today the NY Times has a follow up on that which looks at fresh data on this topic. There is now some evidence that the mutant strain can spread more rapidly in humans than the original strain.

One mutation near the beginning of the pandemic did make a difference, multiple new findings suggest, helping the virus spread more easily from person to person and making the pandemic harder to stop.

The mutation, known as 614G, was first spotted in eastern China in January and then spread quickly throughout Europe and New York City. Within months, the variant took over much of the world, displacing other variants…

The subtle change in the virus’ genome appears to have had a big ripple effect, said David Engelthaler, a geneticist at the Translational Genomics Research Institute in Arizona. “When all is said and done, it could be that this mutation is what made the pandemic,” he said.

The piece is not saying this mutant strain made anyone sicker. And it’s likely that the original strain was contagious enough that it still would have circled the globe, albeit at a less rapid pace. But the Times cites three recent studies which all suggest the mutation spreads more quickly:

One study found that outbreaks in communities in the United Kingdom grew faster when seeded by the 614G variant than when seeded by its Wuhan ancestor. Another reported that hamsters infected each other more quickly when exposed to the variant. And in a third, the variant infected human bronchial and nasal tissue in a cell-culture dish far more efficiently than its ancestor.

Looking specifically at the abstract for that first study, what it found was that people infected with the 614G variant had a higher viral load, suggesting the virus was spreading to more tissue and potentially making the infected person shed more of the virus to others. That study also relied on the largest database of coronavirus genomes in the world. The lead author says that 614G was definitely spreading about 20 percent faster:

“When we look at clusters, the G variant grows more quickly,” said Erik M. Volz, a researcher at the Medical Research Council Center for Global Infectious Disease Analysis at Imperial College London and the leader of the study…

The 614G variant clearly won the race, the analysis found. The precise rate remains uncertain, but the most likely value gives 614G roughly a 20 percent advantage in its exponential rate of growth.

I don’t want to go beyond what the research says but this does raise some interesting questions. Remember that the first areas of the U.S. that were seeded with the virus were on the west coast. But the strain there was the earlier strain, known as 614D, which came over directly from China. It appears that a few people got sick in January and February on the west coast but the virus mostly died out and didn’t spread rapidly the way it later did in New York. New York by contrast mostly got the 614G variant of the virus coming over from Europe. And that strain then spread from New York to the whole country as people fled the city.

Again, it’s too early to draw firm conclusions but it’s interesting and certainly an avenue for future research.

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