We are approaching the time of year when coughs and colds are rampant and everyone seems to be getting sick.
But health experts are warning that this winter could see the worst flu outbreak in decades as a new strain threatens to wreak havoc on the NHS.
The H3N2 strain has been labeled “unpleasant” by health chiefs, who have warned that hospital admissions are already on the rise with flu.
While it has not yet peaked, uptake is increasing at a rate not usually seen until December, and experts worry that many of the most vulnerable may not yet have received their vaccine.
As cases increase, Independent He spoke to Dr. Giuseppe Aragona, general practitioner and medical consultant about how worried we should be about H3N2 and how to prevent it.
What is the H3N2 strain?
H3N2 is a strain of the flu virus that is known to be one of the two most widely circulating strains. According to the UK Health Safety Agency (UKHSA), this strain, also known as subtype K, is currently the most dominant strain in the UK.
Dr. Aragona explained that the letters and numbers refer to the surface proteins of the virus, hemagglutinin (H) and neuraminidase (N).
That particular combination can sometimes cause more severe illness, especially in older people or those with underlying medical conditions, he said.
He added: H3N2 changes regularly, so the version of the virus circulating this year may be different from previous years or from the version in the seasonal vaccine, which could make people more susceptible.
What is the current flu rate?
The latest figures show that the rate of hospital admissions for flu in England rose to 3.8 per 100,000 people last week, up from 2.4 the previous week, according to data released by the UKHSA.
While that’s well below the highs reached in recent years, adoption levels don’t usually start until next month. Experts say this is evidence that the current flu season has started “unusually early” and we could be bracing for a tough winter.
It also follows the biggest flu season in Australian history, which is often seen as an accurate prediction of what the UK can expect.
Why is H3N2 so bad this winter?
Dr. Aragona said there are several different reasons why the flu is so bad this winter.
He first explained that the flu season has started earlier than usual, giving the virus more time to spread.
It has also “evolved” from last year’s strain, he added, meaning that previous immunity or even the vaccine may be less protective than usual.
“In recent years, fewer people have been exposed to the flu, especially children, which makes more people vulnerable,” he said. Additionally, colder weather, indoor mingling, and social habits all contribute to faster transmission, creating a perfect storm for higher flu rates.
Earlier this week, experts warned that the strain developed seven new mutations over the summer, meaning it is completely different from the previous strain included in this year’s vaccine.
The UK is bracing for a wave of flu deaths this winter, with NHS leaders urging people to protect themselves by issuing a ‘flu SOS’.
How can you prevent getting the flu?
Dr. Aragona said the “most effective” way to protect yourself against H3N2 is to get a flu shot — especially if you’re in a “high-risk group” like over 65, pregnant, very young or living a long-term health condition.
He said: “This vaccine may not prevent every infection, but it significantly reduces the risk of severe illness and hospitalization.”
Dr. Aragona added that protection can be improved by practicing hand hygiene, covering the mouth and nose when coughing or sneezing, avoiding close contact with sick people, and properly ventilating the home.
New data published by the UKHSA this week shows that the 2025-2026 vaccine is currently 70-75% effective in preventing hospital admissions in children aged two to 17 years and 30-40% in adults.
Dr Jamie Lopez Bernal, consultant immunization epidemiologist at the UKHSA, said the results provide “reassuring evidence” that seasonal flu vaccines can provide important protection despite concerns about the new substrain.
He “strongly” encouraged everyone eligible to get the flu shot “as soon as possible,” calling it the “best defense” against serious illness.
“Influenza can be an unpleasant infection for many and a life-threatening infection for some,” said Dr. Thomas Waite, vice chief of medicine. Vaccination is the best form of defense.
“Preliminary data from the UKHSA shows that this year’s vaccine continues to provide good protection against common flu strains this year. The flu season has started early this year. Now is the time to get vaccinated if you’re eligible.”
How worried should we really be about H3N2?
Dr Aragona said while the flu can be “unpleasant” for most healthy adults and children, he cautioned against panic because it is usually “manageable”.
“However, for the elderly, people with chronic illnesses and other vulnerable groups, H3N2 can be serious and this season may put more pressure on health services due to the early onset and characteristics of the strain,” he said.
The important thing is to be vigilant: get vaccinated, take reasonable precautions, and seek help early if symptoms become severe. With these steps, risk can be effectively managed, even in a flu year.
