Flu cases have surged dramatically across the United States as the nation faces its most severe influenza outbreak since 2018. Health officials report that millions of Americans have already fallen ill, resulting in increased pressure on hospitals as winter approaches its peak. The US Centers for Disease Control and Prevention (CDC) indicates that influenza activity has escalated unexpectedly early this season, leading to a sharp rise in both outpatient visits and emergency department admissions.
The CDC’s data reveals that flu cases are rising rapidly nationwide, prompting concerns about the capacity of healthcare systems if this trend continues into January and February, traditionally the peak months for flu activity. The current flu season mirrors troubling trends observed in Europe and parts of Asia, raising alarms among public health experts.
According to a report by The Guardian, it remains uncertain whether more Americans will contract the flu this season or if infections are simply occurring within a condensed timeframe. However, the public health impact is already significant, with over 3,100 deaths attributed to influenza in the year ending in August 2025, underscoring the virus’s ongoing threat.
The latest increase follows a particularly severe 2024–25 flu season, which the CDC classified as high-severity and the most intense since the 2017–18 season. That winter recorded 279 influenza-associated pediatric deaths, the highest number ever reported to the agency during a seasonal epidemic. During that season, tens of millions were infected, with hundreds of thousands requiring hospitalization.
Public health experts attribute the intensity of recent flu seasons to a combination of factors, including fluctuating vaccination rates, increased travel, and shifts in immunity due to disruptions in virus circulation during the Covid-19 pandemic.
Monitoring New Flu Strain H3N2 Subclade K
Health officials are closely monitoring a new strain of influenza A known as H3N2 subclade K, which has become the dominant virus circulating in the US. According to data from the CDC and international surveillance, this strain accounts for approximately 90 percent of flu cases across the nation. Emerging earlier this year, H3N2 subclade K has been linked to severe outbreaks in Japan and parts of Europe. Experts warn that this strain contains mutations that may enable it to evade immunity from previous infections and vaccinations, although vaccination remains effective in reducing severe illness, hospitalization, and death.
By mid-December, the CDC estimated there had already been 7.5 million flu cases and 81,000 hospitalisations in the US this season. At least 29 states are now reporting ‘high’ or ‘very high’ levels of influenza-like illness according to the CDC’s FluView surveillance report. Some hospitals, particularly in states like New York, have reported record weekly flu admissions.
As the flu season progresses, health officials caution that the most challenging weeks may still lie ahead, with peak flu activity typically occurring in January or February. Epidemiologist Jennifer Nuzzo from Brown University emphasized the strain on hospitals, stating, “A lot of people are getting the flu at the same time, which is always tough. That can be harder than a season where cases are spread out.”
Officials continue to encourage Americans who have not yet received a flu vaccine to do so, noting that even late vaccination can mitigate the impact of the season. Although the H3N2 subclade K strain was not included in this year’s vaccine, experts stress that the shot still provides critical protection against severe illness.
As of early December, approximately 130 million flu vaccine doses had been distributed, which is 13 million fewer than the same time last year. This decline in vaccination rates raises concerns that a lower uptake could exacerbate the impact of this flu season.
Experts assert, “It’s not too late to get the flu vaccine,” highlighting that even partial protection can make a significant difference, particularly for vulnerable populations such as young children, older adults, and individuals with underlying health conditions.
As winter unfolds, public health officials stress that heightened awareness, vaccination, and early treatment will be essential to prevent hospitals from becoming overwhelmed during what could be another challenging flu season.
