Anearly mutation likely made virus worse

As the coronavirus swept across theworld, it picked up random alterations to its genetic sequence. Like meaningless typos in a script, most of those mutations made no difference in how the virus behaved.

But 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 andmaking 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.

For months, scientists have been fiercely debating why. Researchers at Los Alamos National Laboratory argued in May that the variant had probably evolved the ability to infect people more efficiently. Many were skeptical, arguing that the variant may have been simply lucky, appearing more often by chance in large epidemics, like northern Italy’s, that seeded outbreaks elsewhere.

But a host of newresearch — including close genetic analysis of outbreaks and labwork with hamsters and human lung tissue — has supported the view that the mutated virus did in fact have a distinct advantage, infecting people more easily than the original variant detected in Wuhan, China.

There is no evidence that a coronavirus with the 614G mutation causes more severe symptoms, kills more people or complicates the development of vaccines. Nor do the findings change the reality that places that quickly and aggressively enacted lockdowns and encouraged measures like social distancing and masks have fared far better than the those that did not.

But the subtle change in the virus’s genome appears to have had a big ripple effect, said David Engel thaler, 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 first outbreaks of the virus would have spread around the world even without the mutation, believe most researchers, including Engel thaler. The original variant spotted in Wuhan in late 2019 was already highly contagious, he said. But the mutation appears to have made the pandemic spread farther and faster than it would have without it.

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.

Kristian Andersen, a geneticist at Scripps Research, La Jolla, said the research did show that the variant is more transmissible, but he believes the difference is subtle.

Even so, Andersen said that the variant’s higher transmissibility could help explain why some countries that were initially successful in containing the virus became susceptible to it later. The virus may have been “harder to contain than the first time around,” he said.

“What you used to do may not be quite enough to control it,” Andersen said. “Don’t necessarily expect that the enemy of two months ago is thee nemy you have the next time.”