Super flu VERDICT from Britain’s top scientists – everything you need to know

Doctors are warning that a fast spreading strain of flu, known as H3N2, is driving an unusually severe influenza season and could prove deadly in rare cases, including among otherwise healthy children.
Health experts say the virus has mutated in a way that makes it more aggressive and easier to spread, with concerns that infections could rise further as people mix indoors with family and friends in the run up to Christmas. While vaccines continue to offer strong protection and significantly reduce the risk of serious illness, case numbers are already far higher than in recent years.
The Royal College of Paediatrics and Child Health has warned that the strain can, in very rare cases, lead to serious complications such as sepsis in children.
Virologists explain that influenza viruses constantly change, which means immunity from previous years can become less effective. Professor Ed Hutchinson, from the University of Glasgow’s Centre for Virus Research, said the H3N2 strain circulating this winter picked up an unusually high number of mutations towards the end of the southern hemisphere flu season.
As a result, the UK entered winter with lower population immunity to H3N2 than normal, allowing the virus to spread earlier and more quickly. While there is no evidence the strain is inherently more dangerous than previous versions, the sheer number of infections means more people are becoming seriously unwell.
Dr Leon Peto, a consultant in infectious diseases at Oxford Population Health, said current figures suggest this could be the worst flu season in over a decade. He stressed the need for better evidence on how to treat patients hospitalised with flu, similar to the rapid research advances made during the Covid 19 pandemic.
Professor Nicola Lewis, director of the World Influenza Centre at the Francis Crick Institute, said it is too early to know whether the flu season will last longer than usual or burn out early. However, she urged people not to delay vaccination, warning that the circulating H3N2 subclade is different enough from previous strains to increase the risk of infection and severe illness in those who are unvaccinated.
Experts also highlighted the impact on vulnerable groups. Professor Shereen Hussein, from the London School of Hygiene and Tropical Medicine, encouraged families to take simple precautions such as checking in on older relatives, ensuring vaccinations are up to date, improving ventilation indoors and avoiding visits when unwell.
She stressed that while people should avoid unnecessary hospital visits, no one should delay seeking urgent medical care if they experience severe breathlessness, chest pain, sudden confusion or rapid deterioration.
Dr Vanessa Tobert, an infectious diseases registrar and researcher at the University of Oxford, said hospital admissions for flu have nearly doubled in a week. Despite differences between the vaccine and the dominant strain, she said vaccination is still providing good protection and preventing serious outcomes at rates seen in typical flu seasons.
Dr Lindsay Broadbent, a virologist at the University of Surrey, added that waning immunity in the community may be contributing to the surge, as H3N2 has not been the dominant strain in recent years. An early start to the season has also meant some of the most vulnerable people may not yet have been vaccinated.
Paediatric infectious disease specialist Professor Elizabeth Whittaker, from Imperial College London, said hospitals are already extremely busy and warned that children have been particularly affected. She urged parents to ensure eligible children and pregnant women receive the free flu vaccine as soon as possible.
She added that parents should seek medical advice if a child’s fever lasts more than five days, or returns after initially settling.
Health officials continue to stress that vaccination, staying home when unwell, good hand and respiratory hygiene, ventilation and mask use in crowded or high risk settings remain the most effective ways to limit the spread of flu this winter.