Beds have been closed at Mid Yorkshire Hospitals Trust by the winter vomiting bug norovirus.
Latest figures show 20 beds were closed at Pinderfields, Pontefract and Dewsbury hospitals over the weekend of December 12 after patients displayed symptoms of the highly contagious bug.
The trust has been struggling to cope with demand after a 15 per cent increase in the number of patients going to A&E departments.
Operations have been cancelled and rising numbers of people have been waiting for more than four hours to be seen in A&E.
NHS England figures show that 187 patients waited for between four and 12 hours in A&E in the week ending December 14, up from 113 the previous week.
Between December 12 and 14, 20 beds were closed due to patients having norovirus symptoms, which include vomiting and diarrhoea.
Over the same weekend 47 ambulances were also delayed for more than 30 minutes when handing over patients for treatment at A&E departments, NHS England figures show.
Helen Hey, deputy chief nurse at The Mid Yorkshire Hospitals NHS Trust, said: “We had up to five beds closed across all sites for a maximum of one day over the last weekend.
“All patients with either non-confirmed or confirmed infections were contained and managed in single side rooms, meaning that our available bed base was unaffected due to infection.”
Mid Yorkshire has appealed for people only to go to A&E in a genuine emergency, and to seek help from GPs, pharmacists or NHS walk-in centres if they have non-urgent problems.
Help is also available from the non-emergency helpline NHS 111.
People are also advised not to visit relatives in hospital if they have symptoms like vomiting and diarrhoea.
For advice on norovirus log on to www.nhs.uk/conditions/Norovirus