Has the flu peaked? What the numbers tell us

The NHS remains on high alert over flu, health officials say, but there are clear signs the virus’s rise has ended, at least for now.

Community spread appears to have stabilized, according to the UK Health Security Agency.

Meanwhile, the rise in hospitalized cases has slowed. And with just over 3,000 patients in hospital in England with the virus, NHS chief executive Sir Jim Mackay’s gloomy prediction of “between 5,000 and 8,000” cases has failed to materialise.

So how serious is this flu season so far, and how does it actually compare to previous outbreaks of the virus?

The main difference between the 2025 flu season and the past three years is that the virus began spreading a few weeks earlier than normal.

When a person goes to their GP or hospital with flu-like symptoms, they can be swabbed and tested for flu, Covid, RSV and other viruses.

The UKHSA then records the percentage of these tests that come back positive for flu.

The numbers had increased rapidly during the fall and early winter.

But in the past week, the spread of the virus appears to have stabilized at an average level, according to the UKHSA.

It’s too early to tell if this marks the start of the peak. The flu is unpredictable; a lull can be followed by another flare-up.

The situation in all four UK countries is similar.

Some virologists have linked the earlier flu season this year to the type of virus that is circulating, known as H3N2.

Historically, seasons dominated by this strain tend to be more severe, with greater numbers of hospitalizations among older adults, in particular.

H3N2 has not been the main form of flu detected in the UK for three years, which could mean population immunity is lower.

Scientists also spotted a new change in the genetic makeup of the virus over the summer.

This could have given the virus a head start in the fall.

The name “super flu” has been used by the NHS to describe this latest outbreak.

But it’s not a medical term and it doesn’t mean that the virus itself has suddenly become more dangerous or more difficult to treat.

“It’s misleading and a bit scary to call this a super flu; it’s just a variant of flu that is clearly a little more contagious than normal,” says Professor Lawrence Young, professor of molecular oncology at the University of Warwick.

“What we’re seeing is a flu season that’s coming maybe two to three weeks earlier than normal.”

Separately, the NHS also records the number of sickest flu patients in hospital over the winter. Trends in hospital data tend to lag community spread because it takes some time before people become sick enough to seek hospital care.

Figures from last week show the number reached 3,140 in England, an 18% increase on the previous week. But that was after a 55% rise the previous week.

Although the national figure masks what is happening in different regions, some areas are seeing numbers decline and others are still experiencing large increases.

People over 85 are five times more likely to be hospitalized than the general population.

It’s difficult to compare outbreaks over decades because testing has improved in recent years, so an increase in hospitalizations over time could also reflect better detection.

But estimated flu death figures show that some winters have been particularly harsh over the past 20 years.

In 2017-18, for example, an estimated 25,000 people died from the virus in England, with care homes and the elderly worst affected.

That year, an unusual form of the influenza B virus began circulating and the “Beast from the East” brought freezing temperatures to the UK, creating the perfect environment for the disease to spread.

Three years previously, in 2014-15, modeling by UKHSA scientists estimated that 35,000 people had died, making it one of the deadliest flu seasons in decades.

Again, this was blamed on an outbreak of the H3N2 form of the virus and a seasonal vaccine that was not well suited to the exact form of the disease circulating.

So far, nothing in the data suggests anything comparable in 2025, but we won’t know for sure until the first estimates of flu deaths for this season are released in the new year.

The message from doctors and the NHS is that millions of people continue to demand a flu vaccine.

Even though the genetic makeup of the virus has changed, the main vaccine is still believed to provide an effective level of protection, particularly against hospitalization for severe illness.

The flu vaccine is free in the NHS for people over 65, young children, pregnant women, people with certain health conditions, carers and frontline health and social workers.

All other adults can receive the same vaccine for between £15 and £25 from high street pharmacists.

The latest data shows that as of December 14, more than 70% of elderly and care home residents had taken up the offer of a free vaccine.

But vaccination rates in some other groups are much lower.

So far this year, only 45% of all frontline NHS workers in England have been vaccinated.