A New, More Contagious COVID-19 Strain Has Been Reported in the U.K

Anew strain of COVID-19 reported in the United Kingdom has been blamed for a sharp uptick of cases—prompting new lockdowns in London and more than 40 countries to ban cross-border travel from the U.K.

Although scientists say there is no evidence that the new strain is more deadly, Prime Minister Boris Johnson said it could be up to 70% more transmissible than others, while the health secretary said it was “getting out of control.”

At least 40 countries including the entire European Union and Canada have temporarily banned incoming travel from the U.K. as of Monday.

And the new strain has been detected in Denmark, Australia and Gibraltar, according to the British government; and in Italy and the Netherlands, according to media reports.

But the U.S. has so far not stopped incoming travelers from the U.K. or Europe—sparking fears it may have already crossed the Atlantic Ocean.

“Today that variant is getting on a plane and landing at JFK,” said New York Gov. Andrew Cuomo on Dec. 20, referring to New York’s busiest airport. “How many times in life do you have to make the same mistake before you learn?”

Here’s what to know about the new strain of the virus.

What do we know about the new strain of COVID-19?

The strain was first detected by scientists in early December, according to the U.K. Health Secretary Matt Hancock. He first announced it on Dec. 14, saying that it was prominent in areas where the virus was spreading faster than expected.

Retrospective analysis found the strain was first present in the U.K. as early as September, according to the government.

By Dec. 19, scientific advisers to the U.K. government said they had “moderate confidence” that the variant was more transmissible than others, based on several factors including the exponential increase in infections despite lockdown measures. Genomic data suggests transmissibility that is some 71% “higher than other variants,” said a summary released by the U.K. government advisers.

Researchers now believe a mutation to the genes that code for COVID-19’s spike protein, the part of the virus that clings to human cells allowing for infection, likely causes its increased transmissibility, according to a study published Dec. 18.

However, what scientists know about mutation in SARS-CoV-2—the virus that causes COVID-19—is still evolving, as they collect more samples of the virus from cases around the world. The ongoing research means studies are leading to conflicting results about whether specific genetic changes are helping the virus to spread more easily, or cause more disease. In a Nov. 25 paper published in the journal Nature, for example, scientists studied more than 12,000 mutations of SARS-CoV-2 from viruses in 99 countries and concluded that none were more easily spreading from person to person .