(CNN) Only about 1.7 million people in the United States -- less than 1% of the total population -- live in counties where the US Centers for Disease Control and Prevention still recommends universal indoor masking, according to the latest Covid-19 community level data, updated by the CDC on Thursday.
This is about 5 million fewer people than last week, when about 2% of the US population lived in counties considered to have "high" community levels. Two weeks ago, about 7% of the population lived in counties considered to have high community levels. And when the CDC first released the new metrics three weeks ago, it was about 28% of the US population.
According to Thursday's update, nearly 94% of the US population now lives in counties considered to have "low" community levels, where there is no recommendation for masking. The remaining 6% live in counties considered to have "medium" community levels, where the CDC recommends that immunocompromised people and those at high risk for severe disease consider taking extra precautions against Covid-19.
More than a third of the people who live in counties with high community levels are in Kentucky.
The CDC's Covid-19 community levels incorporate new Covid-19 hospitalizations and hospital capacity along with new Covid-19 cases.
However, CDC measures of Covid-19 transmission, based on new cases per capita and test positivity rates -- which previously guided masking recommendations -- show that more than half of US counties still have "high" or "substantial" rates of transmission.
Dr. Anthony Fauci, President Biden's chief medical adviser, said Thursday that he's spoken with scientists in Europe multiple times this week as Covid-19 cases in Europe and Asia trend upward.
Scientists in the UK say that the BA.2 Omicron subvariant is spreading 80% faster than the original Omicron variant and has become the dominant one. It also accounts for nearly a quarter of all new cases in the US.
"We generally follow what goes on in the UK by about two to three weeks. So we've been paying close attention to what's going on there," Fauci, who's also director of the National Institute on Allergy and Infectious Diseases, told CNN's Jake Tapper.
"What they're seeing is an uptick in cases that are related both to the increased transmissibility of the virus, the waning of immunity, but also the fact that they're opening up the way we are here and the way other countries in Europe and other parts of the world we're pulling back on mask mandates and things like that."
CDC Director Dr. Rochelle Walensky also said Thursday that the spread of BA.2 overseas indicates that the US may see an increase in Covid-19 cases and hospitalizations as mitigation measures lift nationwide.
"We're following this very carefully. We might expect as we open up, as well as we relax many of our mitigation strategies, that we may have some increase in cases related to BA.2," she said.
Still, Fauci said it wasn't necessarily too soon for the CDC to have changed the metrics that mask mandates are based on.
"It's not too soon if you observe the caveat that's associated with that. And the caveat is, we need to be flexible, and if in fact we do see a turnaround and a resurgence, we have to be able to pivot and go back to any degree of mitigation that is commensurate with what the situation is," Fauci said.
"We can't just say that 'we are done now; we're going to move on.' We've got to be able to be flexible, because we are dealing with a dynamic situation."
In Europe, Fauci said, even though Covid-19 cases are on the rise, there hasn't been an increase in severe illness. But those are numbers scientists will want to watch.