Hundreds of patients have been contacted after a health care worker at a hospital in Sussex was found to have hepatitis C.
The employee worked in trauma and orthopaedics at the hospital
The employee at the Royal Sussex County Hospital, in Brighton, discovered they had the disease through a routine blood test.
Now 527 patients have received letters from the hospital warning them of the risk and inviting them for a blood test.
Special clinics for hepatitis C-testing are to be run at the hospital on Friday and over the weekend.
Brighton and Sussex University Hospitals NHS Trust said the member of staff worked in trauma and orthopaedics.
As soon as the worker found out about the disease the trust was informed and all procedures that could expose patients to the virus were stopped.
All GPs in the area have been also been contacted about the situation.
The trust said the period covered by the investigation is from January 2000.
Dr Charles Turton, medical director for the trust, said: "We are doing everything we can to make sure none of our patients suffer harm from being treated by this health care worker.
"Fortunately the risks for any patient of getting hepatitis C in this way are very small indeed - less than 1% -so people can be reassured by that.
"I would also like to acknowledge the wholly responsible conduct of the health care worker involved."