Health bosses in Leeds are urging vulnerable residents to protect themselves against flu as cases continue to rise.
Only 40 per cent of under-65s in the city who are at extra risk from the virus have had the vaccination.
Latest figures show 38 people have died with flu across the UK, an increase of 12 in the past week, while the Government is to relaunch a hygiene campaign to combat its spread.
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Most recent figures for Leeds show there were 71 to 100 GP consultations per 100,000 people for flu-like illnesses in Leeds a week and up to 130 in Wakefield.
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In Leeds, experts are warning those eligible to get the vaccine, which protects against seasonal flu and the H1N1 swine flu virus.
In the city 73.4 per cent of people aged over 65 have had the injection but only 40.4 per cent of under-65s in at-risk groups, such as people with an underlying health condition, have.
Figures for pregnant women - all of whom are being recommended to have the jab - are even lower with only 18.9 per cent of those without additional health problems and 35.7 per cent of those at extra risk having had the jab.
NHS Leeds' Public Health consultant Dr Simon Balmer said: "Anyone who is eligible for a flu jab but not yet had it should make an appointment with their GP as the flu jab gives excellent protection against this nasty virus."
Karen Rodger from Chapel Allerton, who became seriously ill after having flu in 1992, is also backing the advice.
She said: "I was in bed for three weeks and could barely stand up.
Because viruses attack your muscles the flu attacked my heart and I ended up spending a week on the coronary care unit in hospital. It took me another four months before I was fully recovered and back to my old self.
"It was one of the worst experiences of my life. I now have my flu jab every year and I'd say to anyone who is eligible for the flu jab to have it so they don't have to go through what I went through."
Doctors in the city have been seeing an increasing number of patients with flu-like symptoms and the advice is for sufferers to stay at home, rest, drink plenty of fluids and take over-the-counter remedies.
Flu cannot be treated with antibiotics and Dr Balmer said patients were not routinely being prescribed antiviral medicines.
"These are only prescribed by a GP to those people who need them to help reduce the ill-effects of the flu. Mostly, these will be patients with other, long-term health conditions like heart problems, respiratory illnesses and diabetes."
He said these were not being given out from hospitals or walk-in centres and anyone with flu should stay away to reduce the spread of the virus.
To arrange a flu vaccination, contact your GP, or if symptoms are worsening, ring NHS Direct on 0845 46 47.