A growing number of hospitals were last week facing pressure on waiting time targets as they dealt with norovirus outbreaks.
Those affected include Addenbrooke's Hospital in Cambridge, Norfolk and Norwich Hospital, Worcestershire Royal Hospital and York Hospital.
Several trusts said the knock-on effect on capacity made it difficult to deal with or admit 98 per cent of accident and emergency patients within four hours, as required.
Hospitals are closing wards and stepping up infection control, with some visiting restrictions.
Worcestershire Royal Hospital was affected badly last winter by norovirus, which returned in September and again last week, closing several wards.
Worcestershire Acute Hospitals trust director of nursing and midwifery Helen Blanchard said: "What we have done differently this year is to stop visiting to all ward areas.
"It was not a problem to this scale last year and it has come earlier."
The trust had a year-to-date performance of 97.6 per cent at the end of October and it has varied from 93-99 per cent in recent weeks, she said.
A spokesperson for Norfolk and Norwich University Hospitals foundation trust said it was affected at the start of November and again last week, with 21 beds put out of use.
Its November A&E performance was 98.2 per cent but he said some patients had been facing 12-hour waits.
York Hospitals foundation trust chief nurse Libby McManus said its outbreak peaked early last week.
The trust has been giving the "clear message" not to visit affected wards. "It makes it very difficult to maintain things like the four-hour target," she said.