One in four working-age adults in England suffering winter bugs have the flu, as the NHS braces for a 'quad-demic' driven by a tidal wave of winter illnesses. 

Surveillance data from the UK Health Security Agency (UKHSA) show one in five tests on Brits of all ages with coughs and colds carried out at the end of last week came back positive for the influenza virus.

This is up from about one in 10 positive tests the previous week, and another sign the virus is spreading among the population.

It comes as health leaders urged those eligible for free flu jabs to take up the offer, with the current uptake well below that experts say is needed to protect the health service from being overwhelmed. 

The latest flu positivity test results, for December 8th, are nearly three times higher than the level recorded at same time last year.

But not all Brits are being hit equally. Flu positivity was 25.7 per cent among tested British adults aged 25 to 54, a rate of about one in four.

This was narrowly beaten by Brits aged 15 to 24 with positivity rate of 26 per cent and children aged five to 14 who had a rate of 30 per cent, the highest of any group.

Flu rates among Brits over the age of 65, who are eligible for a jab on the NHS, hovered at around one in six. 

It comes as separate figures, from NHS England, show the number of people hospitalised with the flu has jumped 70 per cent in just a week. 

NHS data shows almost 1,900 patients were hospitalised with flu every day last week in England on average. 

This is up from an average of 1,100 in the previous week and is 3.5 times more patients than the same time last year. 

To add to the NHS's woes, serious cases of both norovirus and RSV are also on the rise.

With Covid cases also potentially in the mix, Professor Sir Stephen Powis, medical director for NHS England said health chiefs are worried. 

The tidal wave of flu cases and other seasonal viruses hitting hospitals is really concerning for patients and for the NHS — the figures are adding to our "quad-demic" worries,' he said. 

Susan Hopkins, chief medical advisor at UKHSA, said data suggests the threat of an early flu season 'is materialising' and she encouraged those eligible to come forward and get a jab. 

'With winter vaccine uptake not yet reaching the high levels we aim for in some eligible groups — including healthcare workers, our forecasts for infection rates are not getting any brighter,' she said. 

'Taking up the vaccine will prevent putting your seasonal plans in jeopardy – and more importantly, prevent the risk of severe illness and hospitalisation.'

She added: 'The elderly and those with weakened immune systems are most at risk of suffering more serious illness from flu or norovirus, so if you have flu-like symptoms or diarrhoea or vomiting, avoid visiting people in hospital and care homes to prevent passing on the infection in these settings.'

Professor Chris Whitty, chief medical officer for England, said: 'The latest data is clear that flu is rising rapidly, and we are approaching a serious flu wave.'

'Now is the time to get vaccinated if you are eligible.'

People who are aged over 65, those with long term health conditions, pregnant women, care home residents and carers are eligible for a free jab.

There are signs that calls for eligible Brits to roll up their sleeves and get jabbed have been heard.

NHS England said the number of booked flu and Covid vaccinations appointments has more than doubled from 9,452 on Wednesday to 21,144 on Thursday – a 124 per cent increase. 

Fears of a bad flu year come just days after experts warned this year's flu vaccine could be 30 per cent less effective than hoped.

The flu vaccine is changed each year based on data from countries in the southern hemisphere, like Australia and New Zealand ,who have their winter season six months before Britain.

This is because the same types of flu that struck those countries usually goes on to cause the majority of cases in the UK. 

However, sometimes this forecasting is wrong. In 2017, a mismatched flu vaccine was responsible for 50,000 extra deaths in the UK, according to the Office of National Statistics.

Data suggests the flu jab used in the southern hemisphere, which the one being rolled out in the UK is based on, could be up to 30 per cent less effective than normal. 

Experts consider a successful flu jab to be one that prevents people from needing hospital care for the virus in about 7 in 10 cases.

However, data from countries like Australia and New Zealand, suggests the latest jab only stopped 4 in 10 hospitalisations. 

Flu, also called influenza, is responsible for about 40,000 hospitalisations and more than 10,000 deaths in the UK every year, though this can be higher in bad years. 

The symptoms typically include fever, sore throat, muscle aches and a cough.