The rate at which flu patients were admitted to intensive care shot up by 65 per cent in last week, Public Health England (PHE) has said.
And in Scotland, the rate of flu diagnoses in the first month of 2018 was more than four times higher than it was a year earlier, at 107 per 100,000. The figure is more than double last week's rate.
The statistics came as a woman paid tribute to her daughter who died after battling flu at home.
Bethany Walker, 18, contracted pneumonia and was airlifted to hospital in Inverness where she died on 5 January, the BBC reported.
Her mother, Heather Teale, said in a Facebook post: "I am broken, the bottom has fallen out of my world.
"Bethany, I love you to the moon and back, I always have and I always will, you were the best daughter I could have ever wished for and I will always be the proudest mum in the world."
Ms Teale praised Raigmore Hospital staff for giving her daughter "the best possible care".
In England the hospital admission rate rose by half over the first seven days of 2018 compared with the week earlier. The GP consultation rate also rose by nearly four-fifths.
Professor Paul Cosford, PHE's medical director, urged anyone who was eligible to have the flu jab.
PHE said 71.3 per cent of over-65s, 46.9 per cent of adults with long-term health conditions, 45.5 per cent of pregnant women, 40.8 per cent of 3-year-olds and 42 per cent of 2-year-olds had received the vaccine.
Additional reporting by agencies
