WASHINGTON (AP) — The head of the Centers for Disease Control and Prevention made an impassioned plea to Americans Monday not to let their guard down in the fight against COVID-19, warning of a potential fourth wave of the virus and saying she has a recurring feeling “of impending doom.”

Speaking during a virtual White House briefing, Dr. Rochelle Walensky grew emotional as she reflected on her experience treating COVID-19 patients who are alone at the end of their lives.

“We have so much to look forward to, so much promise and potential of where we are and so much reason for hope,” she said. “But right now, I’m scared.”

“I’m going to lose the script, and I’m going to reflect on the recurring feeling I have of impending doom,” she said.

Cases of the virus are up about 10% over the past week from the previous week, to about 60,000 cases per day, with both hospitalizations and deaths ticking up as well, Walensky said. She warned that without immediate action the U.S. could follow European countries into another spike in cases and suffer needless deaths.

“I have to share the truth, and I have to hope and trust you will listen,” she added.

Walensky’s comments came hours before President Joe Biden was to address the nation Monday afternoon with an update on the vaccination effort.

“The president has not held back in calling for governors, leaders, the American people to continue to abide by the public health guidelines,” said White House press secretary Jen Psaki. “He will continue to do that through all of his engagements.”

Walensky and Dr. Anthony Fauci, the nation’s top infectious disease expert, appealed to elected officials, community leaders, and everyday Americans to maintain social distancing measures and mask-wearing.

“We are doing things prematurely,” Fauci said, referring to moves to ease up on restrictions. Walensky appealed to Americans, “Just please hold on a little while longer.”

She added: “We are not powerless, we can change this trajectory of the pandemic.”

Walensky pointed to an uptick in travel and loosening virus restrictions for the increase in cases. “People want to be done with this. I, too, want to be done with this,” Walensky said.

“We’ve seen surges after every single holiday,” she reiterated: “Please limit travel to essential travel for the time being.”

The White House meanwhile is ruling out the creation of a national “vaccine passport” for Americans to verify their immunization status, saying it is leaving it to the private sector to develop a system for people show they’ve been vaccinated. Some other countries are establishing national databases to allow vaccinated people to resume normal activities.

“We do know that there is a segment of the population that is concerned that the government will play too heavy-handed of a role in monitoring their vaccinations,” said White House COVID-19 adviser Andy Slavitt. He said officials are worried that “it would discourage people” from getting vaccinated if the federal government was involved.

The administration, instead, is developing guidelines for such passports, touching on privacy, accuracy and equity, but the White House has not said when those guidelines will be ready.

UCSF Dr. George Rutherford says the uptick in cases is happening more in New England and mid-Atlantic but says the flocking of spring breakers to Florida is concerning.

“Florida by the way has the greatest of the UK variant of any state in the country and what happens when all those kids disperse against across college campuses all of the east and south, what’s gonna happen with all that. But it does have the potential for spreading stuff around and feeding the fourth surge,” Dr. Rutherford said.

He expects the increase in vaccinations and naturally occurring immunity will keep a potential fourth surge from being as big as previous surges and so far we are not seeing any signs of this in California or much of the west.

“But just understand travel is problematic and there are parts of the country where there is ongoing transmission and there are ongoing transmissions with variance and I think people need to be careful and really think twice around here as we enter the spring holidays,” Dr. Rutherford said.

Of course, wear masks, continue with social distance, avoid large poorly ventilated indoor areas, and get vaccinated when it’s your turn.