NEW YORK (AP) — U.S. flu infections surged over the holidays, and health officials are calling it a severe season that is likely to get worse. New government data posted Monday— for flu activity through the week of Christmas— showed that by some measures this season is already surpassing last winter's flu epidemic. COVID-19 infections have also risen, although they remain less common than flu. The extent of the spread was concerning, as 45 states reported high or very high flu activity, up from 30 states just a week prior.

Public health experts suggest that the strain of flu attracting attention is the A H3N2 virus, which is historically known for causing high rates of hospitalization and death among older adults. The troubling aspect of this season is that over 90% of the detected H3N2 infections are linked to a new version known as the subclade K variant, which differs from the strain included in this year's flu vaccinations.

Flu seasons traditionally peak in January or February, making it difficult to assess the full impact of this year’s vaccine mismatch. Last flu season recorded the highest hospitalization rate since the H1N1 pandemic, with child flu deaths at a record 288. So far this season, nine pediatric flu deaths have been reported. For children, emergency department visits for flu-like illness have already surpassed last year's peak levels. According to the CDC, this season has seen at least 11 million illnesses, 120,000 hospitalizations, and 5,000 deaths attributed to flu, making wise vaccination choices critical.

The CDC advises that everyone aged six months and older who has not received their flu vaccine should do so promptly.