Flu cases have surged dramatically across the United States this December, prompting concerns about the capacity of hospitals to manage the influx of patients. This surge follows what health officials have described as the worst influenza season since 2018, creating urgent challenges as winter intensifies. Many Americans are already reported to be ill, with emergency departments experiencing a significant rise in flu-related admissions.
According to the US Centers for Disease Control and Prevention (CDC), influenza activity has escalated nationwide, leading to increased outpatient visits and hospitalisations related to flu-like illnesses. Data indicates that the early surge mirrors patterns observed in Europe and parts of Asia, raising alarms that health systems may become overwhelmed if cases continue to rise into January and February, traditionally the peak period for flu activity.
A report by The Guardian highlights the uncertainty surrounding this flu season. While it is unclear whether more Americans will ultimately contract the flu or if infections are simply occurring within a compressed timeframe, the public health toll is already substantial. The CDC data reveals that more than 3,100 people died from influenza in the year ending August 2025, underscoring the severity of the virus.
The current spike follows the 2024–25 flu season, classified as a high-severity outbreak by the CDC, marking the most severe season since the 2017–18 period. That winter, the CDC recorded 279 influenza-associated paediatric deaths, the highest number ever documented during a seasonal epidemic. Tens of millions of Americans contracted the virus, leading to hundreds of thousands of hospitalisations.
Health experts attribute the intensity of recent flu seasons to several factors, including fluctuating vaccination rates, increased travel, and altered immunity following disrupted virus circulation due to the Covid-19 pandemic. Currently, officials are monitoring a new strain of influenza A known as H3N2 subclade K, which has become the dominant flu virus in the United States. This strain, which emerged earlier this year, accounts for an estimated 90 percent of flu cases nationwide, according to data from CDC and international surveillance.
The H3N2 subclade K has spread rapidly throughout the Northern Hemisphere, resulting in severe outbreaks in countries such as Japan and parts of Europe. Experts warn that this strain carries mutations that may allow it to partially evade immunity from previous infections and vaccinations. Despite this, vaccination remains a crucial tool in reducing severe illness, hospitalisation, and death.
By mid-December, the CDC estimated there had been 7.5 million flu cases and 81,000 hospitalisations in the US this season. At least 29 states report ‘high’ or ‘very high’ levels of influenza-like illness, as noted in the CDC’s FluView surveillance report. Hospitals in states like New York have recorded unprecedented weekly flu admissions.
Looking ahead, health officials caution that the peak flu activity may still be forthcoming, typically occurring in January or February. Jennifer Nuzzo, an epidemiologist at Brown University, emphasized the challenges posed by simultaneous illnesses. “A lot of people are getting the flu at the same time, which is always tough,” she stated, noting that this scenario can be more challenging than a season where cases are spaced out.
Officials are urging Americans who have not yet received a flu vaccination to do so, stressing that even late vaccination can mitigate the impact of the ongoing flu season. Although the H3N2 subclade K strain was not included in this year’s vaccine, experts maintain that the shot still provides essential protection against severe outcomes.
CDC figures indicate that approximately 130 million flu vaccine doses had been distributed by early December, which is 13 million fewer than at the same time last year. This reduction raises concerns that lower vaccine uptake could exacerbate the impact of the current flu season. Experts continue to stress that “it’s not too late to get the flu vaccine,” highlighting the significant difference it can make for vulnerable populations, including young children, older adults, and individuals with underlying health conditions.
As winter progresses, public health officials assert that increased awareness, vaccination, and early treatment will be vital in preventing hospitals from being overwhelmed by what could develop into another challenging flu season.
