Dr. Anthony Fauci, director of the National Institute of Allergy...

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, speaks during a White House Coronavirus Task Force press briefing in the James Brady Press Briefing Room at the White House on Nov. 19 in Washington, DC. Credit: Getty Images/Tasos Katopodis

Top U.S. health officials on Sunday warned that the country could see a coronavirus "surge upon a surge" in the next few weeks after millions traveled and gathered to celebrate Thanksgiving.

Dr. Anthony Fauci, the nation’s top infectious disease expect, said he was pleading with people who traveled this weekend to take all precautions when they return home, including quarantining and getting tested.

"We have to be careful now because there almost certainly is going to be an uptick because of what has happened with the travel," Fauci, director of the National Institute of Allergy and Infectious Diseases, told ABC News’ "This Week." "We understand the importance of families getting together, and it's just something that we have to deal with, that we likely will have an increase in cases as we get into the colder weeks of the winter and as we approach the Christmas season."

Fauci said he expects restrictions — including federal recommendations to avoid celebrating holidays with non-household members and local mask mandates and social distancing guidelines — to be in place through Christmas.

Within the next few weeks, Fauci told host Martha Raddatz, "we may see a surge upon surge of coronavirus infections."

Following public health guidelines could help "blunt these surges" to avoid lockdowns and school closures, Fauci said.

"We don't want to lock down completely but we might have to" in areas with high hospitalization rates, Fauci told NBC’s "Meet The Press."

White House coronavirus task force coordinator Dr. Deborah Birx speaks...

White House coronavirus task force coordinator Dr. Deborah Birx speaks during a White House Coronavirus Task Force press briefing in the James Brady Press Briefing Room at the White House on Nov. 19 in Washington, DC.  Credit: Getty Images/Tasos Katopodis

Fauci’s warnings came as the United States was expected to have its biggest travel day of the pandemic Sunday, with millions expected to return home from family visits. More than 1 million people traveled through American airports the day before Thanksgiving, according to the U.S. Transportation Security Administration.

The country is already in its biggest surge yet, data shows. New daily COVID-19 cases reached a record of 200,000 for the first time Friday. 4 million new cases have been reported since the start of November, double the number recorded in all of October, according to data compiled by Johns Hopkins University. More than 13 million people have been infected and more than 265,000 have died.

Other federal officials echoed Fauci’s remarks Sunday and urged Americans to wear masks, social distance, avoid gatherings and wash their hands.

"It’s going to get worse over the next several weeks, but the actions that we take in the next several days will determine how bad it is," U.S. Surgeon General Jerome Adams told "Fox News Sunday."

Dr. Deborah Birx, the White House’s coronavirus response coordinator, said the task force is "deeply concerned" about the spike in cases after Thanksgiving, especially because there was already "three, four and 10 times as much disease" around the country.

"We know people may have made a mistake over the Thanksgiving time period," Birx told CBS’ "Face The Nation."

"To every American, this is the moment to protect yourself and your family."

Birx said young people who traveled should consider themselves infected and get tested 5 to 10 days after gatherings — the time frame it often takes for the virus to be detected in tests — and avoid seeing others without a mask on.

But the promise of vaccines is a "light at the end of the tunnel," Fauci said. People considered high priority, which could include health care workers, could start getting vaccinated in December, with more Americans getting immunizations in January, February and March.

"So if we can hang together as a country and do these kinds of things to blunt these surges until we get a substantial proportion of the population vaccinated, we can get through this," Fauci told "Meet the Press."

The U.S. Food and Drug Administration is expected to review emergency authorization for two new vaccines next month. A Centers for Disease Control committee will then issue recommendations for how states should distribute the vaccines, including who should get priority.

Adams said he expects "vulnerable, older people in long-term care facilities" to be at the top of the priority list.

Some groups, such as hospitals, schools and employers, could mandate that employees get immunized before they can return to work, Fauci said.

As the transition has begun to President-elect Joe Biden’s administration, Biden should focus on increasing testing capacity for asymptomatic people, who are a major cause of virus spread, Fauci said, adding he wants to see rapid tests that can be done at home without a prescription.

Fauci also said officials should focus on keeping schools open, especially because spread in them is low.

"Close the bars and keep the schools open, is what we say," Fauci told ABC's "This Week."

Fauci's comments came after New York City Mayor Bill de Blasio was criticized for closing city schools. De Blasio announced Sunday he planned to reopen them.

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