Health service leaders have warned of an 'unprecedented' winter flu surge, with hospitals across the UK recording a record number of patients. The wave, which began earlier than usual, is largely attributed to the spread of the influenza A/H3N2 strain, specifically its K subclade.
What is the H3N2 K Variant?
Influenza viruses are categorised into types A and B, with type A responsible for all seasonal flu, including the 2009 H1N1 pandemic. The H3N2 strain has been in circulation since 1968, undergoing constant genetic changes to evade human immune defences. Its latest iteration, known as the K variant, is believed to be behind the sharp rise in cases seen in several European and Asian nations this season.
While the K subclade has rapidly become dominant, medical experts stress there is no evidence it causes more severe illness. However, its impact may be heightened because recent UK flu seasons have been dominated by the A/H1N1 strain, potentially leaving the population with lower immunity against H3N2.
Vaccine Effectiveness and High-Risk Groups
This shift in circulating strain also has implications for vaccine efficacy. Annual flu jabs are developed based on the viruses prevalent the previous year, meaning protection against the currently dominant H3N2 K variant may be reduced. Despite this, health officials strongly emphasise that vaccination remains a crucial tool to prevent severe disease and hospitalisation, urging eligible people to get immunised ahead of the winter peak.
The strain is considered a particular threat to clinically vulnerable groups. Those at greatest risk include:
- People aged 65 and over
- Pregnant women
- Individuals with underlying health conditions
While all age groups are affected, children typically experience the highest infection rates, with around 20% of the population catching flu annually.
Global Spread and NHS Strain
The new variant is widespread, thought to account for around 90% of recent UK flu cases. It has also hit Asia hard; in China, authorities report it constitutes up to 95% of new positive flu tests. Dr Wang Dayan, head of China's National Influenza Centre, stated a national peak was highly likely in early to mid-December, with outbreak numbers significantly higher than the previous season.
In the UK, the surge is placing immense pressure on the NHS. Professor Julian Redhead, national medical director for urgent and emergency care, said cases were 'incredibly high' for this time of year. He warned that ballooning flu cases coinciding with upcoming industrial action could stretch staff 'close to breaking point'. Junior doctors are set to strike from December 17 to 22 in a dispute over pay and training.
NHS chief executive Sir Jim Mackey called the timing of the strikes 'cruel' and 'calculated to cause mayhem' while the service is under extreme pressure, though he acknowledged the 'anger and frustration' among doctors.
Recognising Flu Symptoms
Flu symptoms often appear suddenly and can include:
- A sudden high temperature
- An aching body and headache
- Extreme tiredness or exhaustion
- A dry cough and sore throat
- Loss of appetite, nausea, or stomach pain
- Difficulty sleeping (insomnia)
