She toured the lab at Princeton University where more than 700,000 COVID-19 tests have been processed since the start of the pandemic.
She says they're seeing a higher concentration of cases of the omicron sub-variant BA.2 here in the northeast region of the country.
"We have started to see an uptick in some cases in some areas, as well as an uptick in some of our wastewater surveillance. So these are areas that we're watching very, very carefully. We've seen some very small increases in hospitalizations in some areas, but not in severe disease, not in ICU stays," said Walensky.
"We've seen about 35% of BA.2 across the country. But in the Northeast region, we've seen it at about 50%. It is one of the reasons we're watching so carefully," she continued.
She says while BA-2 is more transmissible, the disease itself doesn't appear to be more severe or vaccine-resistant than the original omicron strain.
She also echoed urgent calls by White House officials for Congress to approve $22 billion in emergency COVID-19 funding.
"We have the tests, we have the vaccines, we have the boosts, and we have the therapeutics. But we need to be able to buy them and we need to be able to deliver them and administer them to the American people. And that is what is at risk if we don't have this funding," said Walensky.
Some Republican lawmakers have said all this should be paid for using the trillions that Congress has already provided in previous pandemic packages.
This is all happening as second booster shots are on the horizon.
"FDA is currently evaluating the data from both Pfizer and Moderna on this fourth shot. And they will - early in April - actually be looking at what boosting might look like for the fall," said Walensky.
She said fall boosters could be a bivalent vaccine that protects against two strains.
She also urged people to get boosted now if they haven't already.
Walensky says without a booster - just the primary series - a person has 50% protection from hospitalization. With a booster that protection goes up to 90%.
Walensky said the U.S. is in a "quieter period" of the pandemic now, but stressed it's not over as the U.S. still tallies around 900 COVID-19 related deaths each day.
"Now is the time to specifically be vigilant," she said. "To watch our wastewater, to watch our case count, to watch how our hospitals are doing, and to make sure we are ready and prepared should we have a new variant or a new fluctuation or uptick of cases arise."