Health chiefs say a norovirus outbreak is leading to 'exceptional pressure' at hospitals across Cardiff and the Vale of Glamorgan.
For the second time this week, the Cardiff and Vale heath board has extended its ban on all visitors at most of its sites across the region.
Restrictions were imposed a week ago following a 'significant' increase in cases.
The ban affects both Barry and Llandough hospitals, including the mental health unit at Hafan y Coed, but it does not affect outpatient appointments.
The Noah's Ark Children's Hospital at UHW in Cardiff is still allowing visitors, with exemptions being made elsewhere for birthing partners and patients who are critically ill or receiving end of life care.
A CAVUHB spokesperson said on Friday: "The impact of the Norovirus outbreak continues to affect a number of wards which is causing exceptional pressure on the system."
"As a result of this challenging position, we have made the difficult decision to continue a No Visiting policy. Again, this is not a decision we have taken lightly, but one that is imperative to protect our patients, staff and visitors and reduce the spread of infection."
The health board says it will review restrictions again next week "if the situation has improved".

Plans are under consideration to build over 200 houses in a sleepy Welsh village
Sanitary disposal bins introduced in men's public toilets following "Bins for Boys" campaign
Officers called to Dinas Powys Woods after young person enters the river
Vale Council signs off placemaking plan for Barry
Plans filed to use Blackweir Fields for a series of live events this summer
Plans filled for controversial housing development in Cowbridge
Cardiff Council pledges to work with new Welsh Government to tackle trouble-plagued hospital
RNLI issues Sully Island safety advice after first call out of the year to the Island
Morio Lounge on course to open at Nell's Point in May
Vale Council appoints specialist contractors to carry out road improvements
Three men jailed for their roles running a drugs line which supplied cocaine in Barry
Police appeal for witnesses after fatal Penarth Road collision
New Beach and country park facilities opened following major investement
RNLI centre at Barry Island welcomes lifeguards back to Whitmore Bay
Severn tidal lagoons progress