NEW YORK – As the holiday season came to a close, the United States experienced a significant spike in influenza cases, prompting health officials to label this flu season as severe with expectations of further deterioration.

According to new data released by the government on Monday, which includes flu activity up to the week of Christmas, the current season is already outpacing last winter’s flu epidemic, which was among the most severe in recent memory.

Alongside the flu, COVID-19 cases have also seen an uptick, as reported by other federal data. However, COVID-19 infections remain less prevalent compared to the flu.

During the Christmas week, 45 states reported high or very high levels of flu activity, a sharp increase from 30 states just the previous week.

Experts in public health suggest that the type of flu virus circulating may be contributing to the increased numbers.

The focus is on one particular flu virus, A H3N2, which has historically led to the highest rates of hospitalization and fatalities among the elderly. Alarmingly, this season, over 90% of the H3N2 cases examined are linked to a new variant known as the subclade K, which is different from the strain targeted by this year’s flu vaccines.

Flu seasons often don’t peak until January or February, so it’s too early to know how big a problem that mismatch will be.

Last flu season was bad, with the overall flu hospitalization rate the highest since the H1N1 flu pandemic 15 years ago. Child flu deaths reached 288, the worst recorded for regular U.S. flu season.

Nine pediatric flu deaths have been reported so far this season. For children, the percentage of emergency department visits due to flu has already surpassed the highest mark seen during the 2024-2025 season.

The percentage of doctor’s office and medical clinic visits that were due to flu-like illness also was higher late last month than at any point during the previous flu season.

The U.S. Centers for Disease Control and Prevention estimates at least 11 million illnesses, 120,000 hospitalizations and 5,000 deaths from flu have already occurred this season.

The agency recommends that everyone 6 months and older who has not yet been vaccinated this season get an annual influenza vaccine.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education and the Robert Wood Johnson Foundation. The AP is solely responsible for all content.