The UK is in the grip of its worst flu season for seven years, figures show.
In England the numbers going to their GP with suspected flu rose by 40% over the past week, while Wales, Scotland and Northern Ireland have also seen increases.
The last time there was more flu circulating than this was in 2010-11 when swine flu, responsible for the pandemic of the year before, came back.
Hospitals are also seeing “very high” rates of admissions, officials said.
However, it appears the strain known as “Aussie flu” is not causing the most serious illnesses, according to the weekly report up to last Sunday from Public Health England.
Instead – of the four strains circulating – a B strain, which does not normally cause high rates of severe illness, is responsible for about half the hospital cases.
Prof Paul Cosford, of PHE, said while there was a lot of flu circulating it was not at epidemic levels – and there were signs the flu season maybe beginning to peak as the rate of increase was slowing down.
“The best form of protection against flu is to get the vaccine, if you are eligible, and to practice good hand hygiene.”
He also said that mortality rates seemed to be lower than they were in two of the last three winters.
What is flu?
Flu symptoms can come on very quickly and can last for a week or more.
Symptoms include a fever – temperature above 38C – aches, headache, tiredness, a chesty cough, tummy pain and loss of appetite.
Children can also get pain in their ears and appear lacking in energy.
Flu can be particularly unpleasant for certain people, such as the over-65s, pregnant women and those with other serious health conditions.
NHS pressures beginning to ease
Despite the the rising levels of flu the NHS has begun to get on top of the pressures being seen in A&E units.
The weekly data showed the number of times ambulances have been delayed waiting outside A&E fell by nearly a quarter compared to the previous week to 12,500.
Bed closures due to the vomiting bug norovirus have also fallen.
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However, NHS England warned the cold snap expected to hit the north of England over the next few days could lead to an increase in illnesses.
The North East, North West and Yorkshire and Humber have been put on the second highest level of alert with icy conditions and heavy snow forecast up to Sunday.The warning comes as hospitals remain incredibly busy despite the slight easing in pressures.
Bed occupancy levels remain well above the safe level of 85%. Last week an average of 95% was seen.
But the fall in ambulance delays and norovirus at least offers some hope to hospitals that the worst of winter may be behind them.
An NHS England spokesman said: “Today’s figures show pressures abating somewhat compared to the prior week and with hospitals generally continuing to cope.”