The number of cases of flu recorded in England and Wales increased by more than 40% in the last week of December, doctors have revealed.
In the week ending 26 December, the ratio was 124.4 cases per 100,000 people. The previous week's ratio was 85.8 per 100,000.
The figures were published by the Royal College of General Practitioners, which said the only age group in which no increase was recorded was school children. A substantial increase was noted in the 45-64 age group.
A spokesman for the Department of Health said: "These figures are in keeping with what we would expect during a winter flu season. But everyone can do their bit to help keep well. Simple measures like washing your hands help stop flu spreading.
"The Chief Medical Officer has issued clear advice to get the seasonal flu jab if you are in a vulnerable group, particularly pregnant women and people with an underlying health condition, as well as those aged 65 and over.
"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 at-risk groups."