(NEXSTAR) – Centers for Disease Control and Prevention Director Rochelle Walensky said Monday that she continues to be worried about the trajectory of COVID-19 in the U.S., despite increasing progress in vaccinating the country.

“The apparent leveling off of cases and hospital admissions after the consistent declines we saw in these outcomes in early January through the end of February, I consider to be very concerning,” she said during a COVID-19 briefing.

“In addition, while deaths continue to drop, they remain at elevated levels … with some states and regions of the country, such as the northeast and upper midwest, beginning to see a significant rise in cases.”

WATCH NOW: Dr. Fauci and Dr. Walensky are joined by Andy Slavitt for this morning’s COVID-19 briefing. https://t.co/mvjAs2iWsH

— White House COVID-19 Response Team (@WHCOVIDResponse) March 22, 2021

Walensky called the statistics “a warning sign for the American people.”

“As I’ve stated before, the continued relaxation of prevention measures while cases are still high and concerning variants are spreading rapidly throughout the U.S. is a serious threat to the progress we’ve made as a country.”

Walensky cited specifically the so-called “West Coast variants,” B1427 and B1429, which she said account for 52 percent of cases in California and 41 percent of cases in Nevada.

The B117 variant, which originated in the U.K., is now responsible for nine percent of cases in New Jersey and eight percent of cases in Florida, she added.

“Believe me, I get it, we all want to return to our everyday activities and spend time with our family, friends and loved ones,” she said. “But we must find the fortitude to hang in there for just a little bit longer.”

Walensky said “we are at a critical point in this pandemic, a fork in the road, where we as a country must decide which path we are going to take.”

“We must act now, and I am worried that if we don’t take the right actions now, we will have another avoidable surge, just as we are seeing in Europe right now.”

Looking to Europe, Walensky said “we just don’t want to be at this rapid uptick of cases again. And that is very possible that that could happen.”

She closed by encouraging people to continue observing public health measures — such as masking and social distancing — and reminded people that “now is not the time to travel.”

The current seven-day moving average of new COVID cases is 53,200 — a 78.7 percent decrease compared with the highest peak on January 11, 2021, the CDC said.