GPs are being advised to prescribe antiviral drugs for flu after large increases in the number of people reporting symptoms of the virus.
The advice, from the Department of Health and the Health Protection Agency, is a precautionary measure, with experts saying that an epidemic is unlikely.
Doctors are being asked to prescribe the drugs for people most at risk of developing complications from the flu infection, such as the elderly, small children and those with long-term illnesses.
Dr Richard Pebody, of the Health Protection Agency, said it was important that high-risk patients have a 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," he said.
"However, it is difficult to avoid infection if there is a lot of flu circulating."
The Royal College of GPs said that its members had reported a rise in the number of consultations about flu-like symptoms from 16.5 per 100,000 in the last week of November to 27.6 per 100,000 in the first week of December.
NHS Direct has also reported a large increase in the number of calls about colds, flu, fevers and sore throats, which have more than doubled in the past three months.