PHILADELPHIA (CNN) — More than a million passengers have traveled through US airports daily for at least 11 days in a row, according to data from the Transportation Security Administration — at a time that experts say cases of a dangerous variant are climbing across the country.

The TSA says it screened 1,543,115 people at airports nationwide on Sunday, a pandemic-era record that topped a record set only two days earlier.

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“What we’re doing is essentially spreading the B.1.1.7 variant across the nation,” Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine, told CNN.

The spread of variants, in combination with the still small percentage of fully vaccinated Americans, is why experts have stressed state leaders should not be lifting Covid-19 measures just yet — and Americans should be doubling down on safety measures, to avoid another surge of the virus.

But while at least a dozen governors have eased restrictions this month and cases across the US are no longer seeing the steep declines recorded earlier this year, one expert says it’s unlikely the US will see another Covid-19 surge.

That’s because the number of prior infections and now vaccinations in the US have begun to form “enough of a backstop” to prevent another spike, Dr. Scott Gottlieb, the former Food and Drug Administration commissioner, told CBS’s “Face the Nation.”

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“I think what you could see is a plateauing for a period of time before we continue on a downward decline — in large part because B.1.1.7 is becoming more prevalent, in large part because we’re pulling back too quickly, with respect to taking off our masks and lifting the mitigation,” he said.

Other experts have said that plateauing of cases the US is reporting could serve as a predictor for another surge. Emergency physician Dr. Leana Wen told CNN last week she believes the US could be on the cusp of another surge.

Others say it’s difficult to predict what will happen.

“It’s very hard to say,” Hotez told CNN. “We’re in a race, that’s what it comes down to. We’ve gotten a single dose (of Covid-19 vaccine) into about a quarter of the US population … and it could go either way right now.

“This is why it’s really important for the governors to stay the course and to implement masks and social distancing.”

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