A CDC report reveals that 30 states have reached the highest flu activity tier, raising concerns about the pandemic-level severity of this flu season.
Story Highlights
- 30 states are now in the “very high” flu activity tier, up from 45 the previous week.
- The dominant A(H3N2) subclade K variant drives the surge, mismatched with current vaccines.
- 11 million illnesses, 120,000 hospitalizations, and 5,000 deaths have been reported so far.
- CDC urges vaccination despite the vaccine mismatch.
Flu Season Reaches Pandemic-Level Severity
As of the week ending December 25, 2025, 30 states have been classified in the “very high” flu activity tier according to the CDC. This surge follows a week where 45 states reported high or very high activity.
The flu’s rapid spread is attributed to the A(H3N2) subclade K variant, which is not well-matched by this season’s vaccines. With 11 million illnesses and 120,000 hospitalizations already reported, the numbers have surpassed last season’s peak.
30 states are in CDC’s worst tier for flu as ‘super’ variant spreadshttps://t.co/sGPyFl2RMs
— The Hill (@thehill) January 6, 2026
The CDC’s data highlights a particularly sharp increase in pediatric emergency visits, which now exceed the peaks of the 2024-2025 season. The subclade K variant’s dominance—accounting for approximately 90% of characterized A(H3N2) viruses—poses significant challenges, especially since it differs antigenically from the vaccine strains.
This mismatch raises concerns of increased hospitalizations among vulnerable groups, particularly older adults and children.
CDC’s Response and Public Health Concerns
The CDC has been actively tracking the genetic characterization of flu samples since late September 2025, when subclade K emerged as the predominant strain. Despite the vaccine mismatch, the CDC continues to urge vaccination, emphasizing that some protection is better than none.
The vaccines for the 2025-2026 season, targeting A(H1N1), A(H3N2), and B/Victoria, may still offer partial protection against severe outcomes.
Public health experts warn of a potentially severe flu season if subclade K continues to evade immunity. The CDC’s low-confidence prediction of moderate severity reflects uncertainties in the variant’s full impact.
Given the strain on healthcare systems, the CDC has emphasized the importance of flu vaccinations and antiviral treatments to mitigate the burden on hospitals and clinics.
Impact on Communities and Healthcare Systems
The surge in flu cases has led to overloaded emergency departments and clinics, with significant economic and social impacts.
As the flu spreads across 47 states, healthcare systems face unprecedented strain, and absenteeism due to illness disrupts various sectors. The political implications are also significant, with increased pressure on public health funding and vaccine access.
Experts stress the importance of monitoring flu activity and ensuring that healthcare providers are prepared to manage the rising number of cases. The demand for vaccines and antivirals is expected to increase, putting further pressure on pharmaceutical industries to meet the healthcare needs of affected communities.
Sources:
30 states now in worst tier for CDC flu designation as cases spike across the nation
Florida joins CDC’s highest flu activity tier as cases surge nationwide
ABC News: Flu activity continues to climb in the US
