Flu levels are starting to surge
Doctors are being advised to prescribe antiviral drugs for flu in response to increasing numbers of people falling ill with the virus.
Both NHS Direct and the Royal College of GPs have reported large increases in the number of people with influenza symptoms.
The Health Protection Agency have also reported 23 outbreaks in hospitals, schools and care homes.
But experts said the levels of flu were not unexpected for the time of year.
GP surveillance showed a 60% increase in influenza-like illness from 16.5 per 100,00 consultation to 27.6.
NHS Direct has also seen a big rise in calls about flu - with figures more than doubling in the past three months.
In the past week, the proportion of calls about colds or flu increased from 0.9% of the total to 1.2%.
There is currently no significant influenza activity in Scotland or Wales. Figures in Northern Ireland although low, have begun to rise.
The Health Protection Agency said the figures had tipped the threshold when they ask GPs to prescribe anti-retroviral drugs oseltamivir and zanamivir in people at risk of developing serious complications from flu infection, such as the elderly or those with underlying conditions like asthma or heart disease.
The drugs are only recommended when flu is known to be circulating
Dr Richard Pebody, a flu expert from the Health Protection Agency, said: "For most people, flu is miserable, lasting a week or so, but not life threatening.
"For those in at-risk groups, however, such as the elderly and patients with heart problems, diabetes or lung, liver or renal diseases, or those who have weak immune systems, it can be far more dangerous and can lead to more serious illnesses."
Symptoms of seasonal flu include sudden onset of headache, fever, and symptoms such as cough, sore throat, aching muscles and joints.
Dr Pebody said: "If you do get flu this year, our advice is to stay at home, rest, drink plenty of fluids and use over-the-counter remedies if they make you feel more comfortable.
He also advised the elderly and those with chronic illnesses, such as heart disease and diabetes to make sure they have had their flu vaccination.
"Antiviral drugs are only effective if taken within 48 hours of the onset of symptoms and may help limit the impact of some symptoms and reduce the potential for serious complications.
"However, it is difficult to avoid infection if there is a lot of flu circulating."
Flu expert Professor John Oxford, said rates of colds and flu had certainly started to go up but it was not unexpected for the time of year.
"It is not good news but these levels are normal around Christmas time.
"This is an advance warning for anyone who had not been vaccinated - there's a good vaccine supply this year so they should book an appointment with their GP."