The director of the Centres for Disease Control and Prevention suggested testing people for the coronavirus before US domestic flights could help to reduce transmission.
Requiring travellers to receive a negative coronavirus test before boarding domestic flights could be “another mitigation measure”, CDC director Dr Rochelle Walensky said on Monday.
Dr Walensky did not say whether the CDC would move forward with the policy, which the Biden administration is actively considering.
Transport Secretary Pete Buttigieg told Axios the discussion is continuing and the decision would be “guided by data, by science, by medicine and by the input of the people who are actually going to have to carry this out”.
Federal health officials have been watching for more evidence that a variant of the coronavirus now widespread in the UK will become the dominant strain in the US.
Dr Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases, said that could happen by the end of March.
So far, 699 variant cases have been identified, 690 of which are the strain discovered in Britain.
Dr Walensky said the US expected to at least triple its sequencing in the next weeks, giving it a better snapshot of how widely the variants might have already spread in the US.
“Once we have more sequencing that’s happening, we’ll have a better idea as to how many variants there are and what proportion are out there,” she said.
Dr Walensky advised state and local officials against loosening restrictions despite a decline in Covid cases.
Iowa Governor Kim Reynolds at the weekend lifted the law making masks mandatory and other guidelines implemented amid a surge of cases in the autumn.
“I’m asking everyone to please keep your guard up," Dr Walensky said. "The continued proliferation of variants remains a great concern."
The administration plans to release guidance on reopening schools in coming days, she said.
Officials also urged patience as Covid-19 vaccines are distributed.
More than 17 million vaccine doses have been administered to people 65 and older, said Andy Slavitt, senior adviser to the Biden administration’s coronavirus response team.
A federal initiative to vaccinate residents and employees of long-term care homes has delivered 4.8 million doses to 3.7 million people so far, Mr Slavitt said.
Dozens of states are redistributing doses that were meant for the programme and are going unused. Mr Slavitt did not say how many total doses were set aside for it.
Dr Fauci opposed the idea of administering only one of two required vaccine doses to expand capacity.
Trial data indicates the immune response is far greater after someone receives both doses, and cutting it to one could inadvertently create new mutant strains, he said.