Overview: A Season of Unprecedented Velocity
As we review the CDC’s Week 52 FluView data (ending December 27, 2025), the trend is unmistakable: we are facing a “moderately severe” season that is moving with significantly more velocity than the previous two years.
The most alarming feature of the current 2025–26 season is its geographic synchronization. Unlike the 2024–25 season, where regional peaks were staggered, we are currently seeing “High” to “Very High” ILI (Influenza-Like Illness) activity in nearly every HHS region simultaneously.
Comparison through Week 52 (Year-over-Year)
To understand the current clinical burden, we have to look at where we stood at this exact point in late December over the last three seasons:
| Metric (Through Week 52) | 2025–26 (Current) | 2024–25 | 2023–24 |
|---|---|---|---|
| Estimated Illnesses | 11,000,000 | 5,300,000 | 7,100,000 |
| Hospitalizations | 120,000 | 63,000 | 73,000 |
| Total Deaths | 5,000 | 2,700 | 4,500 |
| Clinical Positivity | 32.9% | 18.7% | 17.5% |
| Pediatric Deaths | 9 | 11 | 20 |
The “Synchronized” Surge: Why This Matters
In a typical flu season, the virus moves in a “traveling wave”—peaking in the Southeast before migrating North and West. This year, we are observing geographic synchrony.
- National Ignition: Data shows influenza is “growing or likely growing” in 47 states simultaneously. This is not a traveling wave; it is a nationwide surge.
- The Subclade K Driver: This synchrony is likely driven by the emergence of H3N2 subclade K. Because this variant shows significant antigenic drift from the current vaccine, it has found a broadly susceptible population across all regions at once.
- Systemic Strain: Synchronized surges are more dangerous to the healthcare infrastructure. In staggered seasons, resources (staffing, ventilators, antivirals) can be shifted between regions. In a synchronized surge, every major metropolitan area hits peak capacity at the same time, removing the “relief valve” of inter-regional support.
Three Critical Clinical Observations
1. The H3N2 Drifting Variant: Approximately 91% of subtyped samples are A(H3N2). With ~90% of these belonging to subclade K, clinicians should anticipate a higher volume of “breakthrough” infections in vaccinated patients, though the vaccine remains our best tool for reducing the severity of those breakthroughs.
2. The Hospitalization Burden: The hospitalization rate is nearly double that of Week 52 last year. Region 8 (Mountain states) is currently reporting a staggering 45.5% positivity rate, a leading indicator for the rest of the country.
3. Pediatric Vigilance: While reported pediatric deaths (9) appear lower than the 20 reported in 2023, pediatric ER visits for ILI have hit a 15-year high for December. Given the standard 2-week reporting lag for pediatric mortality, we must prepare for a sharp rise in these figures throughout January.
Clinical Recommendations
- Empiric Antivirals: Given the 32.9% positivity rate, do not wait for lab confirmation to start antivirals in high-risk patients or those with severe symptoms.
- Capacity Planning: Review internal protocols for surge capacity, as the synchronized nature of this peak means local and regional transfer options may be limited.
- Patient Education: Reiterate that while the vaccine may have lower efficacy against infection this year due to the H3N2 drift, it is still significantly reducing the risk of ICU admission and death.
For further reading on the evaluation and treatment of influenza-like illness:
Influenza in the Emergency Department: 2020 Update
Pediatric Influenza in the Emergency Department: Diagnosis and Management
Influenza in Urgent Care: 2024-2025 Season Update (Pharmacology CME and Infectious Disease CME)
Sam Ashoo, MD, FACEP, is board certified in emergency medicine and clinical informatics. He serves as EB Medicine’s editor-in-chief of interactive clinical pathways and FOAMEd blog, and host of EB Medicine’s EMplify podcast. Follow him below for more…
