Dec. 27 (UPI) — Dr. Anthony Fauci on Sunday warned of a “post-seasonal surge” of COVID-19 cases following holiday gatherings as the United States nears 19 million cases.

When asked during an appearance on CNN’s State of the Union if he believes the “worst is still yet to come” in the pandemic Fauci, the director of the National Institute of Allergy and Infectious Diseases, said “I do” citing high levels of holiday travel.

“We very well might see a post-seasonal — in the sense of Christmas, New Years — surge,” Fauci said. “We’re really at a very critical point. If you put more pressure on the system by what might be a post-seasonal surge because of the traveling and the likely congregating of people for, you know the good warm purposes of being together for the holidays, it’s very tough for people to not do that.”

The United States added 226,274 new positive COVID-19 cases and 1,663 new deaths on Saturday, with a total 19,093,241 infections and 332,723 fatalities so far Sunday since the start of the pandemic, according to data gathered by Johns Hopkins University. Cases passed 18 million on Monday.

Despite the world-leading totals of cases and deaths, the Transportation Security Administration said it screened 1,128,773 people at airports throughout the nation on Saturday, after a record 1.2 million people were screened on Wednesday.

International travel also remains a concern as federal regulators in the United States ordered on Friday that all air travelers from Britain must test negative for COVID-19 no more than 72 hours before their flight, following the discovery of a new strain of the virus in the country.

Fauci on Sunday said it was a “prudent” move to place some form of restriction on travel from Britain after many countries have banned travel from the country but said that both British and American officials have found the new strain “doesn’t appear” to make people more ill.

“Obviously, this is something we always take seriously and it’s concerning whenever you get a mutation but I think the American public needs to remember and realize that these are RNA viruses and continually mutating all the time. Most of the time the mutations don’t have a functional significance,” he said.

California leads the nation with 2,122,806 cases, adding 50,141 new cases reported Sunday. The state also reported 237 more deaths, bringing its total to 24,220 since the start of the pandemic — third in the nation.

Texas is second in cases and deaths after reporting 6,105 new cases for a total of 1,476,674 and 51 new deaths totaling 26,472.

On Sunday, Texas House Speaker Dennis Bonnen announced on Facebook that he and his wife, Kim, had tested positive for coronavirus. Bonnen said his symptoms were mild, while his wife’s were “difficult but manageable,” adding they could not pinpoint their initial exposure as they held Christmas celebrations within their own household and have followed health protocols since March.

“This disease is no joke in its unpredictability and severity, so please continue to keep your guard up and your loved ones protected,” he wrote. “Mask up social distance, avoid large gatherings and take care of one another.”

Third-place Florida reported 7,391 new cases, its fewest total since Nov. 30, for a total of 1,271,979 as well as 77 new resident deaths for a total of 21,212.

The state’s positive test rate, however, rose to 9.69% on 65,939 tests on Saturday, the highest since Dec. 14, while hospitalizations rose to 6,367 as of 11 a.m. Sunday, an increase of 731 over 24 hours.

Illinois recorded the nation’s fourth-highest case total at after reporting 3,767 new cases totaling 937,909 and 104 new deaths for a total of 15,969

New York ranks fifth in cases as Gov. Andrew Cuomo announced the state reported 7,623 new confirmed cases for a total of 922,145 while holding the nation’s highest death toll at 29,511 including 115 new deaths.