Flu cases could be heading towards rates not seen for eight years
The number of cases identified by GPs is now also 73 per cent higher than at the same time last year.
The virus is also hitting greater numbers of elderly people, increasing the risk of fatalities, the Royal College of GPs warns.
Experts advised everyone over the age of 65 to ensure that they were vaccinated against the illness.
Around a quarter of elderly people are estimated to be unprotected from the bug, which can cause potentially deadly secondary infections, including pneumonia.
Cases of flu have risen significantly in recent weeks, placing the health service under increasing strain.
The latest figures from surveillance by the RCGP show that there were 69 GP consultations for flu per 100,000 people last week, up from 39.5 per 100,000 on December 14.
Experts have blamed the unseasonably cold start to the winter for encouraging the flu virus to take hold.
Dr Douglas Fleming, director of the RCGP research unit in Birmingham, described the rise in cases as “significant”.
“In the past ten years, the only substantial outbreak was in 1999/2000,” he said. “I think we could be looking at something that approaches that this year.”
Professor David Salisbury, the Government’s director of immunisation, advised anyone eligible for the flu vaccine to ask for it from their doctor.
Professor Steve Field, chairman of the RCGP, said that the increasing instance of the illness among the elderly was “worrying”.
“Older people are more at risk of suffering dangerous complications, including pneumonia and serious chest infections and, of course, we know that influenza can kill the elderly,” he added.
Dr Lorna Layward, from Research into Ageing, the research arm of Help the Aged, said that influenza killed between 3,000 and 4,000 older people every winter but that that figure could reach 30,000 to 40,000 during an epidemic.
A flu outbreak officially becomes an epidemic when there are 200 cases per 100,000 people.
Andrew Lansley, the shadow health secretary, said: “In recent years the Government has rather complacently assumed that winter crises don’t happen anymore, but it has not been since 1999 that we have seen a serious flu outbreak over the winter.
“I know the NHS will respond well, but I continue to regret that ministers have allowed bed numbers to fall sharply and have talked of centralising accident and emergency capacity without paying proper regard to the risks of times of extreme pressure.”