The US should prepare for a “surge upon a surge” in coronavirus cases as millions of travellers return home after the Thanksgiving holiday, top US scientist Anthony Fauci warned on November 29.

The US is the world’s worst-affected country, with 266,831 Covid-19 deaths, and President Donald Trump’s administration has issued conflicting messages on mask-wearing, travel and the danger posed by the virus.

“There almost certainly is going to be an uptick because of what has happened with the travel,” Fauci told CNN’s State of the Union.

Travel surrounding November 26’s Thanksgiving holiday made this the busiest week in US airports since the pandemic began.

“We may see a surge upon a surge” in two or three weeks, Fauci added. “We don’t want to frighten people, but that’s the reality.”

The trend is ominous, Fauci and other government scientists said, with the Christmas holidays sure to bring more travel and family gatherings.

Deborah Birx, White House coronavirus response coordinator, noted a surge in Covid-19 after a holiday weekend in May.

“Now we’re entering this post-Thanksgiving surge with three, four and 10 times as much disease across the country,’ she told CBS’s Face the Nation .

“We are deeply worried.”

The US surgeon general, Jerome Adams, was equally blunt.

“I want to be straight . . . it’s going to get worse over the next several weeks,” he told Fox News Sunday.

As of November 30, the US added 140,651 Covid-19 cases, taking its total to 13,373,673, according to Johns Hopkins University. There had been 822 additional deaths.