Initial tests have confirmed the presence of the Winter Vomiting Virus at Waterford Regional Hospital.
The South Eastern Health Board (SEHB) has appealed to the public to stay away from the hospital. It said there were two new suspected cases of the virus among patients and five new suspected cases among staff.
Thirty-two patients and 32 staff have reported symptoms consistent with the virus. "Of these, nine patients are still in isolation and 11 members of staff are still off work," the SEHB said.
The SEHB cancelled all non-urgent admissions up until last week in a bid to halt the spread of the virus.
The hospital has been closed to visitors, apart from exceptional circumstances, and security staff are in place at the entrances to the hospital.