Cwm Taf Health Board says patients who may have been treated by a healthcare worker infected with Hepatitis C at the old East Glamorgan Hospital in Pontypridd will be asked to ring a dedicated helpline to arrange an appointment in a specialist nurse clinic.
Nicola John, director of public health at Cwm Taf Health Board, said: "We know this will be a very worrying time for patients who may have received obstetric and gynaecology treatment at East Glamorgan General Hospital between May and July 1984."
"However, we want to stress the risk of transmission to patients is small. But it is important that we get in touch with patients who may have been in contact with this worker during their treatment, which is why we are writing to some former patients, to ask them to contact the helpline."
The appointments helpline is open from today, from 8am to 8pm, seven days a week. Specialist clinics will start taking place from 13th September 2013 and patients who have tests will get their results in approximately two weeks.
More top news
40,000 people are expected at the motorbike event in the capital this weekend.
The comedian visited the area in 1964 after apparently upsetting people with one of his routines.
The daughter of former Ospreys player Jerry Collins has been pictured recovering in hospital in France after a fatal crash last month.