Children under five are the main victims of the flu latest outbreak, say new figures.
The number of cases of the illness in children aged one to four has soared by 48 per cent in just one week, bringing it to epidemic levels.
In children under five, the rate reached 184 per 100,000, according to figures from GP practices taken by the Royal College of General Practitioners.
And experts fear the number of schoolchildren catching flu could rise when they return to lessons next week.
Hospitals will soon have to start denying critically ill people treatment in intensive care units as they have been swamped with flu patients.
Many are now 'desperately' short of beds and nurses, an NHS pressure group warned last night.
Speaking in the Daily Mail, Geoff Martin, of Health Emergency, said: 'Cuts in recent years to bed and staff numbers have left the NHS dangerously exposed and there is no doubt that many intensive care units will soon have to close to new admissions, putting hundreds of lives at risk.'
The figures have renewed calls for routine flu vaccination of under-fives on the NHS.
Although many children were given the swine flu jab during the pandemic as a one-off measure, independent experts ruled out inclusion of the under-fives in the seasonal programme.
They are due to review the decision again next year.
Health Emergency warned that the flu outbreak could expose a 'desperate' shortage in intensive care capacity.
It claimed that there is currently a lack of intensive care unit beds and specialist nurses which, it said, could put lives at risk if the flu outbreak gathered momentum in the new year.
Mr Martin added: 'We are getting reports of intensive care units in London where up to a quarter of the beds are filled with swine flu cases and the crisis is getting worse by the day.
The Department of Health responded by insisting the NHS was 'coping very well' with the flu outbreak.
A spokesman said: 'Our latest data shows that the number of people with confirmed or suspected flu in critical care beds is 460.
'This represents fewer than one in seven of the total critical care beds available.'
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