The CDC says people planning to travel from the United Kingdom to the US have to test negative for COVID-19 first

• Air travelers coming to the US from the UK must test negative for COVID-19 at least three days before their flight, the CDC said.
• The rule will go into effect on December 28.
• It comes after the UK discovered a new and potentially more transmissible strain of the novel coronavirus.

The Centers for Disease Control and Prevention announced that travelers flying to the US from the United Kingdom will have to test negative for COVID-19 within three days of their flight.

"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," the CDC said.

The measure applies to both US citizens and foreign nationals and airlines will be required to deny boarding to anyone who refuses to take a test.

The order will be signed by President Donald Trump on December 25 and go into effect on December 28.

The measure comes after the UK discovered a new and potentially more transmissible strain of the novel coronavirus.

The new strain could be as much a 70% more transmissible, Matt Hancock, the UK's health minister said.

Several countries have banned travel from the UK altogether. Earlier this week following the news of the new strain, New York Gov. Andrew Cuomo asked several airlines to require travelers heading to the airport from the United Kingdom to be tested.

Airlines like British Airways, Delta Airlines, and Virgin Atlantic already agreed to require a negative COVID-19 test for passengers from the UK that would arrive at New York's John F. Kennedy International Airport.

In March, Trump banned foreign nationals who had been to the UK in the past 14 days from entering the US. The CDC said that the order reduced travel from the UK to the US by 90%.

"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 said.

However, public health experts like Dr. Anthony Fauci have said it's likely that the new strain is already in the US.

"I would not be surprised if it's already here," Fauci said in an interview with PBS NewsHour. "When we start to look for it, we're going to find it."

Some experts have said there is no indication the new strain causes more severe disease.