Twenty-four cases of coronavirus have been confirmed across two hospitals in Swansea.
Ten patients and five members of staff at Morriston Hospital tested positive for the virus in an outbreak over the last few days.
Health chiefs said most of the cases are within cardiac services and described the outbreak as 'localised'.
Routine heart surgery has been suspended at the hospital as a result, with affected patients to be contacted directly.
At Singleton Hospital, nine members of maternity staff have tested positive for Covid-19 and are isolating.
Swansea Bay University Health Board said there have been no confirmed or suspected cases reported at Singleton in the last 24 hours. No patients have tested positive, and wards and beds are all open as normal.
Professor Richard Evans, executive medical director at Swansea Bay University Health Board, said: “The safety of our patients and staff is paramount and we are doing all we can to contain the spread of the virus while minimising the impact on our services.
“However, as a precaution, elective cardiac procedures at Morriston Hospital are being rescheduled. We will continue to closely monitor and manage the situation.”
The health board said strict infection control measures are in place, including contact tracing, testing and the closure of four wards.
Staff who have tested positive - and their contacts - are isolating at home, and patients who have tested positive are being carefully managed, a spokesperson added.
This is the latest in a number of outbreaks at major Welsh hospitals.
ITV Wales' health correspondent James Crichton Smith explains more: