U.S. air travel hit its highest level on Saturday since mid-March, raising fears that the spike in holiday travel will result in another surge in Covid-19 cases and deaths in upcoming weeks.

Even as the coronavirus rages across the country, 1,192,881 people passed through security checkpoints in airports on Saturday, according to the Transportation Security Administration.

Air travel is still down significantly compared to previous years, but surged during the Thanksgiving and Christmas holidays despite warnings from health experts and elected officials to limit travel and family gatherings. 

Dr. Anthony Fauci said on Sunday that the pandemic could likely get worse in the next couple weeks as the U.S. experiences a delayed impact of post-Christmas holiday travel.

“This is what happens. It’s terrible, it’s unfortunate, but it was predictable,” Fauci, one of the nation’s top infectious disease experts, said during an interview on NBC’s “Meet the Press.” 

December was the most deadly and infectious month of the pandemic in the U.S. The country is averaging more than 2,600 deaths each day, according to data from Johns Hopkins University.

Three states have also now found cases of the new, more transmissible coronavirus strain in people with no travel history.

Surgeon General Dr. Jerome Adams urged on Sunday that Americans wear masks and social distance to help temper the projected surge in infections.

“What we do now matters,” Adams said during an interview on CNN. “If you gathered over the holidays outside of your household without a mask, there are still measures you can take right now.”

“You still can self-quarantine. You still can get tested, knowing that greater than 50% of the spread now is among people who are asymptomatic,” he added.