The United States has experienced a significant and sharp increase in influenza activity during December, according to the latest data from the Centers for Disease Control and Prevention (CDC). This worrying spike follows the most severe flu season since 2018, which concluded earlier this year.
A Concerning Spike in Winter Illness
By the 20th of December, the CDC had already estimated 7.5 million flu cases and 81,000 related hospitalisations across the nation. The data revealed a dramatic 25% surge in cases compared to the previous week. Health officials reported that thirty-two states were experiencing "high or very high" levels of influenza-like illness.
Epidemiologist Jennifer Nuzzo from Brown University highlighted the strain this concentrated wave places on healthcare systems. "A lot of people are getting the flu at the same time, which is always tough," Nuzzo stated. "It could be a worse season, in part because more people are going to need care than hospitals can easily deliver."
Context of a Severe Preceding Season and New Variants
This winter's rise in cases comes on the heels of a particularly brutal 2024-2025 flu season. The CDC confirmed it was the most severe in seven years, tragically including 279 paediatric deaths – the highest number reported to the agency during a seasonal flu epidemic. In the year ending August 2025, more than 3,100 people in the US died from the virus.
Complicating matters is the emergence of a new flu variant, known as subclade K. Furthermore, Europe has seen an earlier-than-usual start to its flu season, with high activity reported in December, often a precursor to trends in the US.
Vaccination Concerns and Public Health Advice
A major concern for experts is a potential drop in vaccination rates. The CDC, under Health Secretary Robert F Kennedy Jr, cancelled its campaign encouraging flu shots this season. By early December, approximately 130 million vaccine doses had been distributed in the US, which is 13 million fewer than at the same point last year.
"It’s completely incredulous to me that after experiencing the worst flu season for kids on record... we could head into this flu season... with anything but a robust plan to encourage people to get vaccinated," Nuzzo remarked.
Despite questions about the current vaccine's effectiveness against the latest variant, Nuzzo strongly advises people to get inoculated. "It may protect you less, but it’s likely still going to give you some important protection," she explained. Her bottom-line advice is clear: "If they haven’t gotten vaccinated against the flu, they should get vaccinated, particularly young kids and older adults."
Nuzzo also pointed out that the public should be aware of the availability of at-home flu tests from pharmacies, as antiviral medications are most effective when taken soon after symptoms begin.
