Health experts are worried that the busy holiday weekend will cause another surge in coronavirus cases.

Sunday was the busiest air travel day of the pandemic with nearly 1.1 million people flying in the United States.

Now that Thanksgiving is over, Director of the National Institute for Allergies and Infectious Disease Dr. Anthony Fauci says he does not foresee public health restrictions and recommendations being relaxed by the end of 2020.

Fauci is warning American residents of a double surge of coronavirus cases in the country in the weeks following Thanksgiving and leading up to the Christmas holiday.

He says people need to be careful because there is almost certainly going to be an uptick due to the travel.

Many CityMD and ProHealth offices are already seeing an increase in people coming in to get tested for the coronavirus.

Lines wrapped around buildings, and urgent care center locations are having to close early due to the long lines.

Dr. Adam Fiterstein, chief of Urgent Care ProHealth, says doctors and nurses are giving up their own safety and health to help patients.

"All of our staff have been coming in early and staying later in order for us to help flatten the curve," Fiterstein says.

Teresa Cunney, an X-ray technician at ProHealth in Little Neck, says they are seeing about 100 to 200 people a day.

One patient waiting at the urgent care center says she has to get tested monthly for work and that the Monday after Thanksgiving was busier than usual.

"I guess after the holiday with the weather, everybody stops here," says Xinrong Ga. "But otherwise pretty quick."

Gov. Andrew Cuomo says coronavirus is the "Grinch" of this holiday season.

"The COVID Grinch is an opportunist, and the COVID Grinch sees this as the seasonal viral transmission," Cuomo says.

Fauci says the good news is that the vaccine will begin to be distributed to a portion of American citizens by the end of December.