The Centers for Disease Control and Prevention will require all airline passengers on flights from the U.K. to the U.S. to produce a negative Covid-19 test result before boarding, the agency said late Thursday.
The U.K. has been grappling with a new strain of the coronavirus believed to be more contagious, leading to many countries imposing restrictions on travel from there in an effort to stem its spread.
Whether—and to what extent—the new strain has spread among Americans is unclear, virus experts said, because the U.S. has been slow to analyze the genetic sequence of samples of the virus collected from patients.
Samples of the virus have been sequenced from only about 51,000 of the 17 million confirmed cases of Covid-19 in the U.S. so far, or about 0.03% of cases, the CDC reported this week. In the U.K., by contrast, 125,000 samples have been sequenced, or about 5.6% of the country’s cases. The practice of sequencing the genome of virus samples, known to researchers as virus surveillance, is important because it lets doctors and scientists better determine why outbreaks are happening and helps them more accurately predict how quickly a strain will spread and change. It also helps researchers design more effective vaccines and other treatments, said Neville Sanjana, a researcher at the New York Genome Center who has studied mutant strains of the coronavirus.
“In a pandemic, sequencing is really important because it allows you to know what to focus on,” Mr. Sanjana said. “If a variant is truly more infectious, having that better surveillance allows us to make better guesses as to why, and as we keep rolling out these vaccines, we have to keep tabs on all the variants that come up.”
Under the new rule, which the CDC said would be applied beginning Monday, U.S.-bound air passengers will have to show they tested negative for the coronavirus within the 72 hours before boarding a flight in the U.K., using either a PCR or antigen test. Airlines must deny boarding to passengers who don’t take a test, the CDC said.
Scientists don’t know whether the new coronavirus strain has yet made its way to the U.S. This week, New York health officials began asking hospitals around the state to test for it. “If it’s here we want to know it—we want to isolate it immediately,” Gov. Andrew Cuomo said Tuesday. “Chances are, if it’s been moving globally, it came here.” Historically, pathogen surveillance in the U.S. has been underfunded compared with the U.K., which has made several advances in genomic sequencing in recent decades, said William Hanage, an epidemiologist and evolutionary biologist at Harvard University who specializes in infectious diseases. “What happened with testing in the spring is exactly the same as what’s happening with sequencing now,” Dr. Hanage said. “Genomic sequencing is what would enable us to understand how the virus is mutating, but once again, we’re playing catch-up.” A CDC spokesman didn’t respond to requests for comment Friday. In its Monday statement on the U.K. variant, the agency said that it had launched a national SARS-CoV-2 surveillance program to try to track the various strains of the disease, but the program won’t be fully implemented until January. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, said earlier this week he expected the new variant to circulate in the U.S. if it isn’t doing so already. Dr. Fauci brought up the prospect of requiring a recent negative Covid-19 test for passengers from the U.K. “I would not be surprised if it was already in the United States,” he said in an interview. “Whether or not it’s going to become the dominant isolate, we don’t know.”
Dr. Fauci said he doesn’t believe the variant, if it is in the U.S. already, is a factor in a recent surge of Covid-19 cases. “I think if it was the dominant strain, we would know about it by now,” he said.
He added that his institute plans studies on the variant and that the Centers for Disease Control and Prevention has a SARS-CoV-2 surveillance program that looks for changes in circulating viruses, much as the U.K. does.
“They do surveillance, and so do we,” Dr. Fauci said.
Members of the White House coronavirus task force discussed the possible testing mandate at a meeting in the White House situation room earlier this week, according to people familiar with the matter. CDC Director Robert Redfield raised the issue. Members of the task force recommended the move, while some in the White House expressed concerns about putting a mandate on the airlines, signaling their support for voluntary testing instead, the people said.
But concerns about the new strain of the virus ultimately convinced the administration to impose the testing mandate, especially since airlines were already moving forward on their own to require tests.
Mr. Cuomo on Monday asked airlines to implement testing requirements for all travelers from the U.K. to New York. Delta Air Lines Inc., British Airways and Virgin Atlantic—the three carriers that operate flights from London to John F. Kennedy International Airport—quickly acquiesced.
Delta started requiring tests of all passengers on its flights from the U.K. to Atlanta as well as New York on Thursday. United Airlines Holdings Inc. announced earlier Thursday that it would implement a similar testing requirement beginning Monday.
Before news of the new strain emerged, the Trump administration had been debating for weeks whether it should lift coronavirus-related travel restrictions on the UK and Ireland. The administration was moving toward doing so, but is now expected to delay that decision as a result of the new strain, people familiar with the discussion said.
Virus samples tested so far haven’t detected the new strain, said Trevor Bedford, a genomic epidemiologist at the Fred Hutchinson Cancer Research Center in Seattle, earlier this week, adding “it could well be here at low frequency and just not detected yet.” Epidemiologists and virologists advising the British government say initial evidence indicates the new strain is more contagious than older variants but so far there are no signs it causes more severe cases of Covid-19.
The U.K. strain, while possibly more contagious, is unlikely to be resistant to the antibodies produced by vaccines and the body’s natural immune responses, said Vineet Menachery, a professor of immunology and microbiology at the University of Texas. He added, however, that neither the British strain nor another mutation that appeared in South Africa, has been sufficiently studied in labs to know for sure.
Dozens of countries around the world have moved to curb travel from the U.K.
Earlier this week, the French and British governments reopened their border to trucksfrom the U.K. after shutting it for 48 hours in an effort to limit the spread of the new strain. The closure had led to lines of thousands of trucks, some carrying fresh produce that was spoiling, on roads leading to English Channel ports.
Since Wednesday, all people traveling to France from the U.K. by any means of transport are required to show proof of a negative coronavirus test taken within the previous 72 hours, French and U.K. officials have said.
This article originally appeared on Wall Street Journal