Four people each day are being admitted to Leeds hospitals with swine flu symptoms.
But most do not turn out to have the H1N1 virus when tested, hospital bosses have been told. Only a few of have tested positive.
At one point 45 people each day were turning up at accident and emergency departments in the city with symptoms of the illness.
That number has dropped significantly since the introduction of the new National Pandemic Flu Service helpline, according to Leeds hospitals director of infection prevention and control Ruth Holt.
She was updating a meeting of Leeds Teaching Hospitals NHS Trust directors about the swine flu situation.
Ms Holt said: "We are admitting about four people per day.
"Once tested, we find it's not swine flu but they have been admitted for another reason."
She said the trust was measuring its "Flucon" status, showing the impact the pandemic was having on hospital services. Currently it is Flucon 0, which means preparatory work is being done.
Ms Holt added that current work included a new system to assess patients before they enter the main A&E areas.
She said they were also ready to start a vaccination programme for hospital staff as soon as a vaccine became available, likely to be the end of August.
"We will be targeting high-risk areas – A&E, critical care and paediatrics," she added.
Trust chief executive Maggie Boyle said if there were a large number of patients admitted as emergencies, that would impact on planned operations.
"If this escalates, we will have to make choices about what patients come into the hospital," she said.
Anyone with the symptoms of swine flu, which include a high temperature of 38F or above as well as a cough, sore throat, runny nose, tiredness, loss of appetite, muscle or joint aches and pains, headaches and possibly sickness or diarrhoea, should stay at home.
Unless in a high risk group, the advice is to take over-the-counter remedies. If symptoms don't improve after a day, call the National Pandemic Flu Service which will issue a special number in order to get anti-viral medication if appropriate.
A friend, relative or neighbour should then collect the medicine from their nearest distribution centre.
Those with underlying health problems or who are especially vulnerable should phone – not visit – their GP.
The swine flu symptom checker is at www.direct.gov.uk/pandemicflu or call 0800 1513100.