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".

Vale Councillor blasts school funding in the county
Bear Field Skate Park set for major upgrade as part of new Placemaking Plans
New apprenticeship courses in construction to be introduced in Wales
Former Penarth Bank could become a cafe
New poll shows majority of Welsh voters lack voting confidence ahead of Senedd Election
Construction hub secured for rail upgrades
Prolific thief banned from Holton Road
Cowbridge: plans for more holiday lodges
Man dies suddenly in Romilly Park
Cash boost for Sully Primary School
Speed limits reduced despite objections
Concern over imported chicken in school meals
A48 closed after three-vehicle collision
Rhys unveils red bench 'in living memory'
Barry: plans lodged for 70-home development
Plans to revamp Heritage Coast centre
Carnival drummers join pirate opera encore