As Americans anxiously watch the spread of coronavirus variants that were first identified in Britain and South Africa, scientists are finding a number of new variants that seem to have originated in the United States — and many of them may pose the same kind of extra-contagious threat.
In a study posted on Sunday, a team of researchers reported seven growing lineages of the coronavirus, spotted in states across the country. All of them have evolved a mutation in the same genetic letter.
“There’s clearly something going on with this mutation,” said Jeremy Kamil, a virologist at Louisiana State University Health Sciences Center and a co-author of the new study.
It’s not clear yet whether this shared mutation makes the variants more contagious, but because it appears in a gene that influences how the virus enters human cells, the scientists are highly suspicious.
“I think there’s a clear signature of an evolutionary benefit,” Dr. Kamil said.
It’s not unusual for different genetic lineages to independently evolve in the same direction. Charles Darwin recognized convergent evolution in animals. Virologists have found that it happens with viruses, too. As the coronavirus branches into new variants, researchers are observing Darwin’s theory of evolution in action every day.
It’s difficult to answer even basic questions about how prevalent the new variants are in the United States because the country sequences genomes from less than 1 percent of coronavirus test samples. The researchers found examples scattered across much of the country, but they can’t tell where they first arose.
It’s also hard to say whether the variants are spreading now because they are more contagious, or for some other reason, like holiday travel or superspreader events.
Scientists say the mutation could plausibly affect how easily the virus gets into human cells. But Jason McLellan, a structural biologist at the University of Texas at Austin who was not involved in the study, cautioned that the way that the coronavirus unleashes its harpoons was still fairly mysterious.
“It’s tough to know what these substitutions are doing,” he said of the mutations. “It really needs to be followed up with some additional experimental data.”