Patients in two wards at the hospital became ill last month and tests later confirmed the presence of the potential killer bug.

A spokeswoman for NHS Tayside was unable to say today whether the affected patients were still being treated or had made a full recovery, stating that no personal details would be issued due to confidentiality issues.

However, it was confirmed there are now no cases of E.coli 0157 on the wards, a statement which does not preclude patients continuing to be treated at home by their GP.

Now all patients admitted to Wards 5 and 9 during August are being contacted and advised what to do if they are experiencing symptoms.

All staff who worked on the wards over the period are also being issued with advice.

Former patients and staff are also being offered screening for the bug if they have symptoms of the germ, which can cause diarrhoea (sometimes with blood) sickness, vomiting, stomach pain and fever.

Scotland’s worst case of E.coli 0157 infection happened in 1996 when 21 people died after eating meat contaminated with the germ from a Lanarkshire butcher.

NHS Tayside actively tracks down and monitors infections and was keen to reassure patients today, particularly hoping to avoid alarming those due to be admitted to Ninewells.

A statement advised that the NHS Tayside Health Protection Team is investigating the outbreak and trying to trace recent patients and staff.

It said, “The patients became ill during August 2008. The incubation period is usually around 1 to 14 days.

“As a result of this investigation and as a precautionary measure, Dr Christopher McGuigan, NHS Tayside Consultant in Public Health Medicine, has written to people who were patients in Wards 5 and 9 while affected patients were there.

“The letter advises them that if they have had symptoms within 14 days of leaving either ward they should go to see their own GP who will arrange for a stool sample to be tested.”

Hospital staff and local GPs have also been informed of the situation.

Dr McGuigan said, “If you receive a letter, please do not worry.

“While E. coli O157 can cause a serious infection, we believe the risk of you catching it is very small.

“We are writing to former patients and staff with advice on E. coli O157 infection and we are offering screening for it as a precautionary measure. E. coli O157 can spread easily.

“By taking some simple steps people can help reduce the risk of catching the infection.

“Careful hand washing, especially before eating, after using the toilet and before and after handling food, is one of the most effective ways people can avoid the infection."

Professor Stewart Forsyth, Medical Director of NHS Tayside’s Delivery Unit, also reassured patients and visitors who are due to come to Ninewells.

He said, “We have written to a number of former patients who have spent time in two wards as a precautionary measure.

“If anyone has experienced stomach cramps, loose bowel movements or diarrhoea, sometimes with blood in it, within 14 days of when they left hospital, they should go to see their own GP.”

Anyone who has any questions or concerns can call free on 08000 282 816.