As the coronavirus swept across the world, 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 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.