A new and distinct strain of influenza is circulating across the United Kingdom, prompting doctors to warn the public about a different set of often more severe symptoms. The variant, known as subclade K, is a mutation of the A(H3N2) subtype and is contributing to significant pressure on NHS services this winter.
Rising Hospitalisations and Service Strain
The impact of this flu wave is being felt sharply within the healthcare system. Up to 4 January 2026, an average of 2,924 people were being hospitalised daily with the virus. This surge has led four hospital trusts – three in Surrey and one in Kent – to declare critical incidents due to what they describe as "significant and sustained pressures".
Surrey Heartlands Trust specifically cited high winter demand that was 'exacerbated by increases in flu and norovirus cases'. Echoing the severity of the situation, 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."
Distinct and Concerning Symptoms
Medical professionals are reporting that this subclade K strain presents differently from typical seasonal flu. Key symptoms to watch for include:
- A higher, more persistent fever that can last between five to seven days.
- A severe, phlegmy cough that is difficult to shake.
- Increased instances of gastrointestinal problems like vomiting and diarrhoea in adults.
- Significant muscle and joint aches.
Dr Mark Loafman, speaking to NBC Chicago, noted that patients are experiencing 'more fever with the flu this year than people are accustomed to'. Alarmingly, doctors have observed that these high fevers are sometimes not being effectively reduced by standard over-the-counter treatments like paracetamol or ibuprofen.
Public Health Advice and Vaccination Call
Health authorities are urging the public to remain vigilant and to take protective steps. Professor Pandit 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.”
Health Secretary Wes Streeting reinforced the message, stating: “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."
For those who do fall ill, the NHS advises managing symptoms at home with rest, hydration, and pain relief where appropriate. However, it is crucial to seek medical advice by calling 111 or booking a GP appointment if you are over 65, pregnant, have a long-term condition, or if symptoms do not improve after seven days. Immediate emergency care should be sought for sudden chest pain, severe breathing difficulties, or coughing up blood.
