CASES of flu rose by nearly 50 per cent last week putting NHS services under increasing pressure.
The Royal College of General Practitioners (RCGP) reported that cases of flu in England and Wales reached 124 per 100,000 of the population in the week ending December 26.
There were 86 per 100,000 cases in the previous week.
The increase occurred in all age groups except schoolchildren but there was a substantial increase in those aged 45-64.
Flu levels still fall short of an epidemic, which experts define as 200 cases per 100,000.
Health chiefs in Yorkshire yesterday said services were coming under strain and urged people to think twice before seeking help.
Demand for 999 ambulance services in the region on Monday and Tuesday was 20 per cent higher than normal, making them the busiest days this year so far.
Officials also renewed appeals for more people to get vaccinated against flu amid concerns over lower levels of protection than previous years. However, latest estimates suggest more people have been inoculated against the virus in recent weeks.
At least 27 people have so far died in England from flu this winter, including three from the Hull area.
A Department of Health spokesman said the rise in flu cases was "in keeping with what we would expect during a winter flu season" and claimed the NHS was coping.
"We are pleased to hear from RCGP that their estimates show vaccine coverage in over 65s has now caught up with last year and coverage is still going up in under-65s' in risk groups.
"Our latest data shows that the number of people with confirmed or suspected flu in critical care beds is 460. This represents less than one in seven of the total critical care beds available.
"The NHS is coping very well and only a small percentage of the intensive care capacity is being taken up with patients with flu.
"As a cautionary approach, local health trusts are looking at how they can increase capacity if necessary."
Yorkshire's director of public health Paul Johnstone urged more people in at-risk groups to get vaccinated.
"People in at-risk groups are more likely to develop complications if they catch flu, and the seasonal flu jab will not only protect them, it will also protect their families and the people around them," he said.
Geoffrey Barnes, acting director of public health in North East Lincolnshire, said: "The number of people who have received flu vaccinations in our over-65 population and among those under 65 who are at risk of complications from flu is much lower than we would want or expect this winter."
Yorkshire Ambulance Service said it was concerned high demand earlier this week could be repeated over New Year bank holiday.
In Hull, health chiefs said patients with colds and flu-like symptoms were one of the main reasons behind a significant increase out-of-hours calls to GPs.
An NHS Hull spokeswoman said: "At the current time, the local NHS is coming under significant pressure and we would appeal to anyone who is looking for medical help or advice at this time to consider their options first."