Hospitals Under Pressure as US Flu Cases Explode After Worst Outbreak Since 2018

Flu cases have surged across the United States in December following the country's worst influenza season since 2018, sparking fears that hospitals could face renewed strain just as winter reaches its peak.

Health officials warn that influenza activity has accelerated earlier than expected, with millions of Americans already estimated to have fallen ill and emergency departments reporting sharp rises in flu-related admissions.

According to data from the US Centers for Disease Control and Prevention (CDC), flu activity has risen rapidly nationwide, driving increased outpatient visits, emergency room demand and hospitalisations linked to flu-like illness.

The early surge mirrors trends seen in Europe and parts of Asia and has raised concerns that health systems could struggle if cases continue to climb into January and February, when flu activity traditionally peaks.

A report by The Guardian, citing CDC figures, said it remains unclear whether more Americans will ultimately contract the flu this season or whether infections are simply occurring in a tighter time frame. But the public health toll is already significant.

More than 3,100 people died from influenza in the year ending August 2025, according to CDC data, underscoring the virus's continued lethality.

Worst Flu Season Since 2018 Still Looms Large

The latest spike comes on the heels of the 2024–25 flu season, which the CDC classified as a high-severity outbreak and the most severe since the 2017–18 season.

That winter saw 279 influenza-associated paediatric deaths, the highest number ever reported to the agency during a seasonal epidemic, according to CDC surveillance cited by The Guardian. Tens of millions of Americans were infected, with hundreds of thousands hospitalised.

Public health experts say the intensity of recent seasons has been shaped by a combination of fluctuating vaccination rates, increased travel and shifting immunity following years of disrupted virus circulation during the Covid-19 pandemic.

New Mutated Flu Strain Fuels Rapid Spread

Health officials are now closely monitoring the spread of a new influenza A strain known as H3N2 subclade K, which has become the dominant flu virus circulating in the United States.

According to TODAY, citing CDC and international surveillance data, the strain is now estimated to account for around 90 per cent of flu cases nationwide.

Subclade K emerged earlier this year and spread rapidly across the Northern Hemisphere, driving unusually severe outbreaks in Japan and parts of Europe.

Experts say the strain carries mutations that may allow it to partially evade immunity from prior infections and vaccines, though vaccination remains effective at reducing severe illness, hospitalisation and death.

Hospitals Under Pressure as Peak Approaches

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.

Hospitals in several states, including New York, have recorded record weekly flu admissions, according to TODAY. Health officials warn that the worst may still be ahead, with peak flu activity typically occurring in January or February.

Jennifer Nuzzo, an epidemiologist at Brown University, told The Guardian that large numbers of people falling ill at the same time pose a particular challenge for hospitals.

'A lot of people are getting the flu at the same time, which is always tough,' she said. 'That can be harder than a season where cases are spread out.'

Americans Urged to Get Vaccinated Despite Late Start

Health officials continue to urge Americans who have not yet received a flu jab to do so, warning that even late vaccination can help blunt the impact of the season.

Although the H3N2 subclade K strain was not included in this year's vaccine, experts say the shot still offers important protection against severe illness.

CDC figures show that around 130 million flu vaccine doses had been distributed by early December, 13 million fewer than at the same point last year, raising concerns that reduced uptake could worsen the season's impact.

'It's not too late to get the flu vaccine,' experts told TODAY, stressing that even partial protection can make a significant difference, particularly for young children, older adults and those with underlying health conditions.

As winter continues, public health officials say heightened awareness, vaccination and early treatment will be critical in preventing hospitals from being overwhelmed by what could become another punishing flu season.