Dec. 30 (UPI) -- COVID-19 hospitalizations are on the rise across the United States, as a new variant emerges.

Hospitalizations have increased 4.2% from two weeks ago, with daily intensive care unit admissions rising more than 9% from two weeks ago, NBC News reported. COVID-19 hospitalizations are not expected to reach the level they did last winter, when the original Omicron variant began to spread.

However, according to the Centers for Disease Control and Prevention, a new variant called XBB.1.5, now makes up 40.5% of new infections across the country.

"We're projecting that it's going to be the dominant variant in the Northeast region of the country and that it's going to increase in all regions of the country," said Dr. Barbara Mahon, director of the CDC's proposed Coronavirus and Other Respiratory Viruses Division, in an interview with CBS News.

The agency's 40.5% figure is only a projection, Mahon stressed, with a probability interval ranging right now from 22.7% to 61.0%.

Before evolving into XBB.1.5, XBB had already ranked among the strains with the largest immune-evasion relative to earlier major Omicron strains. Scientists in Japan reported this week that XBB appeared to be "the most profoundly resistant variant" to antibodies from breakthrough infections of any lineage they had tested.

Flu activity has fallen in most areas, according to the CDC. For the week ending Dec. 24, around 18,800 people were hospitalized with flu, down from around 20,700 hospitalizations the week prior.

RSV hospitalization rates have fallen significantly since their peak in mid-November of 5.1 hospitalizations per 100,000 people. For the week ending Dec. 24, the rate was 0.8 per 100,000.