Dec. 25 (UPI) -- Federal regulators have ordered that all air travelers to the United States from Britain must now test negative for COVID-19 no more than 72 hours before the flight.
The new edict, which takes effect on Monday, comes as Britain struggles to control a new coronavirus variant, forcing fresh shutdowns around the country, including London.
The Centers for Disease Control and Prevention ordered the rule change late Thursday.
"Viruses constantly change through mutation, and preliminary analysis in [Britain] suggests that this new variant may be up to 70% more transmissible than previously circulating variants," the CDC said in a statement.
"This new order is consistent with the measures that have been taken so far to increase our ability to detect and contain COVID-19 proactively and aggressively."
Passengers headed for the United States from Britain must show a negative result from either a polymerase chain reaction (PCR) or antigen test within three days before they board the flight.
Airlines must also confirm the negative test results for all passengers before they are allowed to travel. Those who refuse to test will be denied access to the flight.
"This additional testing requirement will fortify our protection of the American public to improve their health and safety and ensure responsible international travel," the CDC added.
According to the European Center for Disease Prevention and Control, the new variant that's appeared in Britain appears to be "significantly more transmissible," but infections are no more severe.
Canada and other nations have also imposed new restrictions on travelers departing from Britain.
Some health experts, like former FDA Commissioner Dr. Stephen Gottlieb and BioNTech CEO Ugur Sahin, have expressed confidence that the coronavirus vaccines approved for use in the United States will also be effective in blocking the new variant.