Health authorities across the United Kingdom have issued a stark warning as a concerning new strain of influenza, identified as subclade K, fuels a significant rise in infections and hospital admissions. The variant, part of the A(H3N2) subtype, is presenting with more severe and persistent symptoms than typical seasonal flu.
Hospital Services Under Pressure
The impact on the NHS is already severe. Data shows that daily hospital admissions for flu patients reached 2,924 per day up to January 4, 2026. The strain on services has forced at least four hospital trusts to declare critical incidents due to "significant and sustained pressures".
Three of the affected trusts are in Surrey: Royal Surrey NHS Foundation Trust, Epsom and St Helier University Hospitals NHS Trust, and Surrey and Sussex Healthcare NHS Trust. Additionally, East Kent Hospitals University NHS Foundation Trust declared a critical incident, citing sustained pressure at the Queen Elizabeth The Queen Mother Hospital in Margate.
Unusual and Severe Symptoms of Subclade K
Medical professionals report that this new flu strain is bringing a different set of challenging symptoms. A key hallmark is a high fever that can persist for up to seven days and, worryingly, may not respond to standard over-the-counter treatments like paracetamol or ibuprofen.
Lung specialist Dr Juanita Mora described the symptoms, stating the variant causes "really high fevers" and a "really bad cough that won't go away, very phlegmy". She also noted the presence of vomiting, diarrhoea, and significant joint and muscle aches.
This increase in gastrointestinal issues is being observed anecdotally among adult patients. Dr Mark Loafman confirmed, "We are seeing... more signs of some GI [gastrointestinal] illness for the adults who have the subclade K strain of flu."
Recognising Flu and Managing Symptoms at Home
The core symptoms of influenza, which often appear suddenly, include:
- A sudden high temperature of 38C or above.
- Aching muscles and joints.
- Extreme tiredness or exhaustion.
- A dry cough, sore throat, and headache.
- Difficulty sleeping, loss of appetite, and potential nausea or diarrhoea.
For most people, managing flu involves self-care at home. The NHS recommends:
- Getting plenty of rest and sleep.
- Keeping warm.
- Drinking lots of water to stay hydrated.
- Taking painkillers like paracetamol or ibuprofen to lower temperature and ease aches.
- Gargling with salt water or drinking hot lemon with honey for a sore throat.
The rapid spread of the subclade K flu strain and its impact on hospital capacity underscores the importance of vigilance. Anyone experiencing severe or prolonged symptoms, particularly a high fever that does not break, is advised to seek medical guidance.
