The CDC estimated that there have been 7.5 million illnesses, 81,000 hospitalizations, and 3,100 deaths related to influenza so far during the 2025-2026 flu season, according to a report released Dec. 20.
In addition, five more pediatric deaths were reported to the CDC in the week ending in Dec. 20, increasing the number of pediatric influenza deaths to eight children.
The increase in cases is partially attributed to a new variant, according to experts. However, providers should be confident in knowing how to treat their patients.
Flu on the Rise Across the Country
Flu activity is high and very high in 32 jurisdictions. Colorado, Louisiana, New York, and South Carolina are at the highest activity levels. Connecticut, Idaho, Massachusetts, Michigan, and New Mexico are at the second-highest activity level (second tier of very high), and Arkansas, Georgia, Maryland, Minnesota, Missouri, New Hampshire, North Carolina, Ohio, Puerto Rico, Rhode Island, and Tennessee are at the third highest level (third tier of very high).
There has been a 25.6% increase in positive cases. That correlates with increases in hospitalization rates—the weekly rate now sits at 22.9 per 100,000 residents and the cumulative hospitalization rate at 18.2 per 100,000 residents—and in the mortality rate, now at 0.5%.
“Seasonal influenza activity is elevated and continues to increase across the country,” the CDC said in the report. “Sustained elevated activity is observed across multiple key activity indicators in all areas of the country.”
However, severity indicators are low at this time, according to the report, although that may change in the coming weeks.
Mostly Flu A
The most commonly circulating strain currently is influenza A. In the week ending in Dec. 20, 22,364 people tested positive for influenza A at clinical laboratories, and 1,249 people tested positive for influenza B.
In the week ending in Dec. 20, public laboratories reported 2,086 cases, the majority of which were influenza A (2,029). Of those influenza A viruses that were subtyped, the most prominent was H3N2 (91.8%). A small percentage (8.2%) were influenza A(H1N1)pdm09.
In addition, a sample of 275 H3N2 viruses collected since Sept. 28 have undergone additional genetic characterization at the CDC. The majority (89.5%) were subclade K.
No avian influenza A(H5) infections were reported to the CDC in the week ending in Dec. 20.
Why Such an Increase
It is respiratory season, so increases in flu cases are to be expected. But why is there such a large increase? H3N2 subclade K is to blame, according to experts. “This flu is something that most of us have not seen, this variant,” said Sharon Nachman, MD, the division chief of pediatric infectious diseases at Stony Brook Children’s Hospital, in New York. “That means your antibodies that you had in the past aren’t going to help protect you so much.”
The current vaccine is also a little bit of a mismatch, she said. “So the extra protection we would have liked to get from the vaccine is not as good as we would like it to be.”
The third reason could be missed vaccinations. “If you have a circulating variant that you’ve never seen before, that you don’t have a whole lot of protection to, and you didn’t get a vaccine either, well, then, of course, you’re going to get it, and you will be sick,” Dr. Nachman said.
Vaccination and Antivirals
The CDC continues to recommend flu vaccination for all people 6 months of age and older. They estimate that 130 million doses of flu vaccine have been administered this year.
The CDC also reminds providers to prescribe antiviral treatments judiciously to treat the flu. “Those should be started as early as possible and are especially important for patients at higher risk for flu-related complications,” it said in the Dec. 20 report.
Dr. Nachman encouraged providers to keep reminding patients to get vaccinated, and to prescribe antivirals when indicated. She gave an example of a toddler in daycare bringing home an illness to a family with a newborn brother or sister. “We want those kids tested because we’re going to give Tamiflu [oseltamivir, Roche] to the infant at home,” she said. “Nobody wants an 8-week-old coming down with the flu. So even if the mom has gotten flu vaccinated, we really want to cocoon that baby.”
Although the numbers are upsetting, Dr. Nachman reminded that clinicians should be confident in their knowledge. The flu is not a mystery, she said. “We know what the virus is. We know how to diagnose it. We know how to treat it. And we know somewhat how to prevent it,” she said. “We know what to do. That’s why we do science.”
Dr. Nachman reported no relevant financial disclosures.