A mutated strain of the flu that spreads particularly quickly could overwhelm hospitals and cause record deaths this winter, experts have warned. 

A potentially dangerous new strain of the virus has emerged and started spreading much earlier than usual in the UK. 

It appears to be easier to catch and pass on and is a 'hotter' and 'nastier' virus that could impact more of the population, specialists say. 

And it could trigger the worst flu season in a decade – surpassing previous years which saw nearly 16,000 people die. 

'We haven't seen a virus like this for a while,' Professor Nicola Lewis, director of the World Influenza Centre at the Francis Crick Institute, told the BBC. 

'These dynamics are unusual. I'm not panicking, but I am worried.' 

The flu virus evolves constantly but in June this year there was a substantial shift, with seven mutations in a strain of H3N2. 

Experts say the form of flu the UK is facing this year is more severe than usual, particularly for older people. 

'H3 is always a hotter virus, it's a nastier virus, it's more impactful on the population,' Professor Lewis added. 

Hospital admissions for flu have already surged by 60 per cent in England over the past week, from 251 to 422, with the rate already at a level not usually seen until the start of December. 

It follows the biggest flu season ever in Australia – with more than 410,000 cases – which is often seen as a guide to what happens in the UK. 

Sir Jim Mackey, chief executive of NHS England, has warned a particularly bad flu season is likely to hit just as the NHS emerges from a five-day doctors' strike. 

Thousands of medics – previously known as junior doctors – are set to walk out from November 14 to November 19 amid a row over pay and conditions. 

The combination of a strike and rampant flu could set hospitals 'at capacity' from December to March, Sir Jim said. 

Health officials have also warned that many people at risk of flu may be unaware they are eligible for a vaccine. 

Only 28.9 per cent of those with a long-term health condition have received this year's jab. Meanwhile, data shows that flu deaths more than doubled in England last year with 7,757 fatalities – up from 3,555 on 2023. 

Duncan Burton, chief nursing officer for England, said: 'We are issuing an urgent SOS to the eligible people who have yet to get jabbed.'