The CDC has no plans to stop flights coming from the UK despite the rise of a new Delta-related variant

• About 6% of Delta cases in England are now of a variant called AY.4.2 - and the figure is rising.
• But the CDC has no plans to stop flights from the UK, its director Dr. Rochelle Walensky said.

The US has no immediate plans to ban flights from the UK or Europe to stop a new Delta-related variant from spreading, the Centers for Disease Control and Prevention (CDC) has said.

"We are not anticipating that now," CDC Director Dr. Rochelle Walensky told NBC's Meet the Press on Sunday, adding that the CDC was "following the science very, very carefully."

Scientists worldwide are carefully examining AY4.2, a descendent of Delta, to see if it is more infectious than Delta, or able to avoid the immune response.

Walensky said that there were a "handful" of AY4.2 cases in the US. It hadn't "taken off" in the US like it had in the UK, she said.

In England, the number of AY4.2 cases has gradually increased in recent weeks, according to a Public Health England report published Friday.

Dr. Jeffrey Barrett, a medical genomics group leader at the Wellcome Trust Sanger Institute, tweeted on October 19 that AY.4.2 was the only Delta descendant that was steadily increasing in the UK, which suggested a "consistent advantage" over Delta.

In the US, the new AY.4.2 variant was in less than 0.05% of sequenced tests. Meanwhile, AY.4, its parent lineage, "represents around 11% of the Delta viruses in the United States," the CDC told Insider Wednesday.

The figure could be higher because the US doesn't sequence every person that catches COVID-19.

The rise of AY.4.2 hasn't yet been seen in other countries. It's not yet clear whether the new variant's rise in the UK is due to the virus' mutations giving it a biological advantage against other variants, or if it is spreading in populations with already high levels of transmission for other reasons.

Dr. Scott Gottlieb, a former commissioner of the Food and Drug Administration, told Face the Nation on Sunday that it could be more contagious than Delta, but not by enough to change the trajectory of the pandemic in the US.