A mutating virus

British Prime Minister Boris Johnson on Monday ordered England into its third lockdown, warning that the nation’s hospitals could become overwhelmed within 21 days. But it wasn’t just an increase in COVID-19 cases that prompted the move—the country is also facing a new, quick-spreading variant of the virus that causes the illness.

The United Kingdom isn’t the only country that has identified the new strain of the coronavirus. New York Gov. Andrew Cuomo on Monday announced a Saratoga Springs, N.Y., man who contracted the disease in December tested positive for the U.K. variant. The man, who is in his 60s, had no known travel history, suggesting the new strain might be established in the state, Cuomo said. Colorado, California, and Florida have also identified cases of the U.K. strain of the virus.

For public health officials, the news is worrying: The variant that surfaced in the United Kingdom in the fall does not seem to be more dangerous, but scientists say it could be much more contagious.

British scientists first observed the U.K. variant, called B117, on Sept. 20 in a patient from Kent, England. In the intervening weeks, the distinct variant has become prevalent in southeast England, according to a preliminary report published in December. The United Kingdom also suspended flights to South Africa after British scientists discovered a unique strain of the virus there.

The B117 variant of the SARS-CoV-2 virus contains at least 17 mutations from the more common variant responsible for the global pandemic, according to an Imperial College in London report. Mutations arise from errors made when the virus duplicates itself in infected human cells. The genetic mutations, common in viruses, can change the character of the disease.

While the Imperial College report said the B117 variant didn’t appear to make people any sicker, U.K. scientists say it is about 50 percent more transmissible from person to person. That means it could cause more deaths—not because it is more deadly, but because more people catch it.

Imperial College researchers have also found the B117 variant is more prevalent in children under the age of 19 than the original virus. That may mean the strain more successfully infects children. But the researchers say it could also reflect the fact that U.K. schools have remained open.

While the B117 variant differs genetically from the original SARS-CoV-2 virus, World Health Organization Chief Scientist Soumya Swaminathan told the BBC in December she expects the currently approved vaccines to protect against it.

But the variant has plenty of time to spread before governments can distribute the vaccines to most people. Speaking on Face the Nation, former U.S. Food and Drug Administration Commissioner Scott Gottlieb said he expects the variant to become the predominant strain of the coronavirus by this spring.

“There’s some estimates that the new variant probably represents about 1 percent of all new cases,” he told CBS. “By March, it’s going to be the majority of infections. It’s going to grow quickly.”