On Nov. 12, 2020, a study published in Science by a team of researchers in the U.S. and Japan showed that the mutant virus, called D614G, was more easily transmitted and grows better within hosts, likely aiding its dominance. It differs from the original virus by just one amino acid, or short string of genetic code, in the spike protein that helps the viruses enter cells to cause infection.

In late 2019, the SARS-CoV-2 virus emerged in China and quickly spread across the world, leading to the COVID-19 pandemic. In early 2020, that virus mutated, likely in Europe, and that mutation was the current dominant form of the virus across the globe.