Masking up
A highly mutated ‘superflu’ strain is driving unprecedented flu hospitalisations across the UK, prompting renewed mask guidance and urgent NHS warnings. Pexels

Britain is facing a sharp return to mask-wearing guidance as an extra-mutated strain known as the 'superflu' drives record hospital admissions and prompts NHS warnings of a historic winter crisis.

The NHS has reported an unusually early start to the flu season, with officials stating that a drifted influenza A(H3N2) strain called 'subclade K' is now dominating cases across the country. This mutated form has proved more infectious than strains seen in previous years and is linked to more severe illness, higher hospital admissions and an increase in people contracting multiple seasonal viruses simultaneously.

NHS leaders have described the situation as heading towards the 'worst winter ever,' with concerns heightened by ongoing strikes and staffing pressures. Much of the rise is believed to have been driven by children aged five to 14, who currently account for a significant share of new infections. The number of patients hospitalised with flu is ten times higher than at the same point in 2023, marking a rapid acceleration that health officials say is unprecedented. Sir Jim Mackey, chief executive of NHS England, has said the pressures will, in a number of ways, resemble the Covid period.

Expert Warnings and Calls for Mask Use

Virology experts, including Professor Nicola Lewis of the Francis Crick Institute, have described the virus as unusual, noting that H3 strains tend to be more impactful on the population. She stated that 'we haven't seen a virus like this for a while,' adding that the current dynamics stand out from recent flu seasons. With infections continuing to rise, the UK Health Security Agency has restated that masks remain a useful measure in limiting the spread of respiratory viruses. Officials issued guidance that anyone feeling unwell should wear a mask, as coverings reduce the number of particles released from the mouth and nose. They noted that masks can also protect the wearer from contracting viruses such as Covid-19 and respiratory syncytial virus. Mandatory mask rules have already returned in parts of hospitals across London, Lincolnshire, Shropshire and Oxfordshire due to growing concern over rising infection numbers.

Hospitals Reintroducing Mask Policies

Trusts including United Lincolnshire Teaching Hospitals NHS Trust now require masks in high-risk areas across sites in Lincoln, Grantham, Boston and Louth to respond to cases of flu, Covid and RSV. The Shrewsbury and Telford Hospital NHS Trust has also requested mask use in emergency departments, cancer wards and neonatal units at its Royal Shrewsbury and Princess Royal hospitals.

Several other trusts have followed similar measures, including Whittington Health NHS Trust in North London, Salisbury District Hospital and Oxford University Hospitals NHS Foundation Trust. NHS Forth Valley in Scotland and the Cwm Taf Morgannwg University Health Board in Wales have also brought back mask rules in some clinical settings.

Record Hospital Admissions and Rising Concerns

Flu hospitalisations in England have reached the highest level ever recorded for this point in the year, with an average of 1,717 patients in beds daily last week, including 69 in critical care. This figure is 56 per cent higher than the equivalent week in 2024 and sits far above 2023, which recorded 160 hospitalised patients at the same stage. Last winter's peak hit 5,408 patients in early January, and the NHS warns that numbers could exceed these records as this year's season has not yet reached its height.

London Hospitalisations Triple as Vaccination Lags

London has seen one of the sharpest rises in infections, with hospitalisations tripling compared to the same time last year. An average of 259 patients in the capital required hospital beds for flu last week, compared with 89 in the equivalent period in 2024. NHS officials stress that vaccination uptake in London is significantly lower than elsewhere, with fewer than half of eligible residents having received their jab.

Over 1.8 million vaccinations were delivered between September and November, though many more people remain eligible. The London Ambulance Service has also recorded its three busiest days of 2025 so far, reporting a 20 per cent rise in calls linked to respiratory infections, including flu. Health leaders maintain that mask use, vaccination and caution in crowded areas remain central tools in slowing the spread of the 'superflu' as the country approaches winter.

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