WASHINGTON, D.C.: Influenza activity across the United States remains low as winter approaches, but health experts say early data is raising red flags: a newly emerged version of the virus is circulating, and vaccination rates may once again fall short of what's needed to prevent another severe season.

CDC data shows that most early infections involve a new form of the type A H3N2 virus, a strain historically linked to the highest hospitalizations and deaths among older adults. Last winter's flu season was one of the deadliest this century, and some specialists fear the country may be heading for a repeat if vaccination coverage remains uneven.

"I think we're going to see a really severe season," said Asefeh Faraz Covelli of the George Washington University School of Nursing.

Early analysis suggests current vaccines may still offer at least partial protection against the new subclade K variant, despite it being different from the strain used to design this year's shots. Experts say even partial protection can reduce illness severity and lower hospitalization rates.

Last winter, the U.S. recorded its highest flu hospitalization rate since the H1N1 pandemic 15 years ago. Flu contributed to more than 18,000 deaths, including a week in which more than 1,800 people died, the largest one-week spike in at least a decade. Childhood flu deaths were also unusually high.

CDC surveillance so far shows only one state, Louisiana, with moderate flu activity. Most early cases have been identified in children, according to CDC flu tracker Alicia Budd.

With travel and family gatherings expected to increase around Thanksgiving, Covelli warned that infections could accelerate quickly. "I think it's going to start picking up here," she said. "This is the ideal time to get vaccinated."

Tracking respiratory infections has been more challenging this year due to a recent government shutdown that paused CDC data reporting during a critical early-season period of viral activity.

At the same time, federal messaging around vaccines has shifted. Public health campaigns have been more limited since the U.S. Health Secretary Robert F. Kennedy Jr., a prominent vaccine skeptic, took charge of federal health agencies. His past claims about vaccine safety, including concerns about the preservative thimerosal, have fueled confusion at a time when steady guidance is needed.

COVID-19 vaccination data underscores the trend: only about six percent of children and 14 percent of adults are up to date with their shots, each figure down roughly three percentage points from last fall.

Flu vaccination patterns are more complex to interpret. IQVIA data suggests that pharmacies administered more than two million fewer flu shots through late October than last year. But CDC survey data shows children's flu vaccination rates are holding steady at 34 percent, and adult rates have climbed slightly to about 37 percent.

CDC officials cautioned that it's still early in the season, making it difficult to predict whether these trends will continue.

As of early November, the nation's flu hospitalization rate is roughly the same as this time last year, while hospitalizations for COVID-19 and RSV remain lower, according to another CDC dataset.