Infection specialists are working on the problem

Three other hospitals in south Wales have experienced difficulties because of the virus, but the step to postpone surgery has only been taken at the Royal Gwent.

The hospital has also asked visitors who have experienced stomach upsets or diarrhoea recently to stay at home.

The gastric virus has also struck at the nearby St Woolos Community Hospital in Newport.

Staff said it normamlly lasts for 48 hours; staff who have been affected by the virus are now beginning to return to work and are immune.

Over Christmas, it also affected the Prince Charles Hospital, more than 30 miles away in Merthyr Tydfil, although the situation there has now returned to normal.

The smaller Barry Community Hospital near Cardiff, was also affected. One ward closed but has since re-opened.

Airborne virus

The Gwent Healthcare NHS Trust decided on Thursday some routine operations at the Royal Gwent would have to be cancelled.

Trust spokesman Alan Davies said around 40 patients and a number of staff were suffering from the airborne virus.

The main problem for us is that to ensure other patients do not get it we are not discharging patients to residential homes of community hospitals

Alan Davies

"The main problem for us is that to ensure other patients do not get the bug we are not discharging patients to residential homes or community hospitals," he said.

Beds on unaffected wards are being freed up for priority patients needing medical and surgical treatment

"The frequent gathering of people at this time of year makes the virus particularly difficult to track," added Mr Davies.

It is hoped the situation will be back to normal within a week."

Staff are now confident they have controlled the bug - there were no new cases overnight.

The source of the virus is unclear, but it appears to have been active in the community before it was brought to the hospital in the Christmas and New Year period.

A spokesman confirmed that the Prince Charles Hospital at Merthyr Tydfil, was now over the worst of the problems experienced there because of the bug.

At one stage during the Christmas holidays, half the staff on one ward were absent because of sickness, and the accident and emergency department was inundated with patients suffering from stomach problems.