Need to knowDoctors say the H3N2 subclade K flu variant has different symptoms to typical flu, including prolonged high fevers lasting up to seven days
11:09, 13 Jan 2026Updated 11:17, 13 Jan 2026
Woman with flu(Image: Getty)
Doctors have warned of a new flu variant causing infections across the UK, with unique symptoms to be aware of. The start of this year saw an increase in hospitalisations due to the flu, with daily admissions reaching 2,924 up until 4 January.
Four hospital trusts have declared critical incidents owing to “significant and sustained pressures” on their services. Three trusts in Surrey and one in Kent are currently under critical incident status.
Surrey Heartlands Trust attributed the high winter pressure to a surge in flu and norovirus cases. NHS national medical director, Professor Meghana Pandit, stated: “It’s clear that the worst is far from over for the NHS this winter, with hospitals again experiencing a rise in patients admitted with flu and other respiratory virus cases last week.”
He further emphasised: “It remains important that people come forward for care as usual and there are still plenty of opportunities to get vaccinated and get protected against flu.”
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The UK Health Secretary Wes Streeting echoed this sentiment: “Flu can be serious, particularly for older people, young children and those with underlying conditions, and vaccination remains the best protection. I urge everyone who is eligible to get their flu jab as soon as possible.”
Doctors have reported different symptoms associated with this new strain of flu. The new virus strain, known as subclade K, is a variant of the A H3N2 subtype of flu.
In the USA, where the strain is also causing problems, Dr Mark Loafman told NBC Chicago that patients are experiencing “more fever with the flu this year than people are accustomed to. And the fever can last up to seven days, so five to seven days. And that’s worrisome”.
Medical professionals say standard treatments such as paracetamol or ibuprofen are sometimes failing to reduce temperatures. Respiratory specialist Dr Juanita Mora explained: “This new strain has symptoms of really high fevers. It has a really bad cough that won’t go away, very phlegmy, and also vomiting and diarrhoea and lots of joint aches as well as muscle aches.”
GPs have noted an increase in patients presenting with gastrointestinal issues including nausea and vomiting. Dr Loafman added: “We are seeing anecdotally more signs of some GI illness for the adults who have the subclade K strain of flu.”
The NHS states that influenza symptoms typically develop rapidly and tend to be more serious than those of an ordinary cold. Whilst most individuals recover within a week, the illness can prove extremely debilitating.
Main Flu SymptomsA sudden high temperature (38C or above).An aching body (muscles and joints).Feeling tired or exhausted.A dry cough.A sore throat.A headache.Difficulty sleeping.Loss of appetite.Nausea, vomiting, or diarrhoea (more common in children).Managing Flu at Home
Most individuals can handle flu symptoms at home without needing to consult a doctor. The NHS suggests the following self-care measures:.
Rest and Sleep: Allow your body the energy required to combat the infection.Stay Warm: Utilise blankets or additional layers to maintain a stable core temperature.Hydrate: Consume ample water to prevent dehydration (your urine should be light yellow or clear).Pain Relief: Use paracetamol or ibuprofen to reduce your temperature and alleviate aches. Avoid taking “all-in-one” flu remedies in conjunction with paracetamol tablets, as you could inadvertently exceed the safe dosage.Soothe a Sore Throat: Adults can gargle with salt water, or drink hot lemon and honey.When to Seek Help
The NHS recommends calling 111 or arranging an urgent GP appointment if
You’re concerned about your baby’s or child’s symptoms.You’re aged 65 or over.You’re pregnant.You have a long-term medical condition (e.g., diabetes, heart/lung disease) or a weakened immune system.Your symptoms don’t improve after 7 days.
Dial 999 or visit A&E immediately if you experience sudden chest pain, severe difficulty breathing, or start coughing up blood.
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