Has flu peaked? UK data show signs of stabilization in 2025 season

UK health officials say the winter flu surge appears to have peaked for now, with community transmission stabilising and hospital admissions slowing as the season progresses. Officials estimate just over 3,000 patients in England are in hospital with flu, a figure that falls short of NHS chief executive Sir Jim Mackay’s earlier forecast of between 5,000 and 8,000.

UK Health Security Agency data show the percentage of swabs testing positive for flu has plateaued at a medium level in recent days, though health chiefs emphasise that it is too early to declare a peak. The pattern is broadly similar across the four nations of the UK, and while the uptick in cases has slowed, experts caution that flu remains unpredictable and a lull can be followed by another surge.

The season’s timing has been unusual, with the virus starting to spread several weeks earlier than normal. Some virologists say the early spread may be linked to the dominant strain this season, known as H3N2, which historically can produce more hospitalisations among older people. H3N2 has not been the main form of flu detected in the UK for three years, which could mean lower background immunity in parts of the population. Over the summer, scientists also noted shifts in the virus’s genetic makeup, a factor that could have helped the autumn surge gain a head start.

Can we call it super-flu? The NHS has used the term informally to describe this outbreak, but experts caution it is not a medical label and does not mean the virus is more dangerous or harder to treat. "It is misleading and a bit frightening to call it super flu; it's just a flu variant that is clearly a little bit more infectious than normal," says Prof Lawrence Young, a molecular oncology expert at the University of Warwick. "What we're seeing is a flu season that's perhaps two to three weeks earlier than normal."

Separately, NHS data show hospital admissions for flu remain a key lagging indicator. Last week, the number of people in hospital with flu rose to 3,140 in England, an 18% increase on the previous week after a 55% jump the week before. The national figure masks regional variation, with some areas seeing declines and others still climbing. Those aged 85 and older are five times more likely to be hospitalised than the general population. While testing and reporting have improved over time, this year’s patterns make direct comparisons with earlier decades difficult; early death estimates for flu seasons can vary widely based on the mix of circulating strains and vaccine effectiveness.

Looking back at historic winters, experts point to years when flu deaths were much higher. In 2017-18, estimates suggest about 25,000 people died in England from flu, with care homes and older adults especially affected, aided by a form of influenza B and cold conditions that enabled spread. In 2014-15, modelling by UKHSA estimated around 35,000 deaths, linked to the H3N2 strain and a vaccine that did not closely match the circulating form. There is nothing in the current data to suggest a similar scale for 2025, but first formal estimates of influenza deaths for this season will not be published until the new year.

Health officials emphasize that vaccination remains the best protection against severe illness. The flu vaccine is free on the NHS for people aged 65 and over, young children, pregnant women, those with certain health conditions, carers, and frontline health and social care workers. All other adults can obtain the same vaccine from high-street pharmacists for about £15–£25. The latest data show that more than 70% of older people and care home residents had received the free jab by 14 December, while vaccination coverage among frontline NHS workers stands at about 45% so far this year.

Public health officials urge millions to stay current with vaccination and to seek medical advice if flu-like symptoms worsen or fail to improve after a few days. While the virus’s genetic makeup has shifted, health authorities say the main jab continues to offer protection against severe disease, particularly for those at higher risk, and vaccination boosters remain an important part of the response as the season evolves.

As the calendar turns, UK health officials say data will continue to be monitored closely. While there is an early sense that the worst of the surge may have passed, they stress that the trajectory of flu remains uncertain and continued vigilance is essential through the coming weeks and into the new year.