Hundreds of patients have been put on alert after it emerged a hospital worker is carrying the potentially fatal hepatitis C virus.

Almost 600 letters have been issued to at-risk patients across Sussex treated in the past three years requesting them to undergo tests.

Extra staff are being drafted in to run the emergency blood screening sessions, which start on Friday.

The worker, employed by Brighton and Sussex University Hospitals NHS Trust, is based at the trauma and orthopaedics department of the Royal Sussex County Hospital in Brighton and has also worked at the Sussex Nuffield Hospital in Woodingdean.

The trust is not naming the person involved, who is now back at work but not dealing with patients.

The alarm was raised when the worker took a routine blood test and immediately informed bosses of the hepatitis C diagnosis.

Trust medical director Charles Turton said: "We are doing everything we can to make sure none of our patients suffer harm from being treated by this worker.

"Fortunately, the risk is very small indeed. It is less than one per cent so people can be reassured by that.

"I would also like to acknowledge the wholly responsible conduct of the healthcare worker involved."

Brighton and Sussex hospitals have sent out 527 letters and the Sussex Nuffield sent out 66.

The records of some 800 patients seen at the Royal Sussex between January 2000 and January 2003 have been checked.

One patient, who received a letter this morning, from the Sussex Nuffield underwent surgery at the private hospital two years ago.

The woman, who does not want to be identified, said: "I'm really shocked. This letter just turned up this morning and has really worried me."

The letter, accompanied with information about the hepatitis C virus, offered the woman a blood test and reassurance that she was at a low risk of contracting the disease.

A mother from Brighton received one of the letters after her son underwent an operation at the Royal Sussex County Hospital two years ago.

The woman said: "This is scary, this is my baby. I phoned the helpline straight away."

About 400,000 people in the UK are diagnosed with hepatitis C but many more may unknowingly carry the virus.

Symptoms include tiredness and sickness, resulting from inflammation of the liver, which can lead to cirrhosis or cancer if it is not treated.

The virus is transmitted by blood-to-blood contact, particularly sharing needles, body piercing, unprotected sex and unscreened blood transfusions.

Local GPs have been informed and other patients with general concerns can call the NHS Direct helpline on 0845 4647 for more information.