Visitors have been urged to stay away from a hospital to contain the spread of the winter vomiting bug, norovirus.
Cardiff and Vale University Health Board has asked members of the public not to attend University Hospital Llandough unless "absolutely necessary" for the next few weeks.
A number of patients across two wards are suffering from the bug, which spreads quickly from person to person and can make more acutely ill or vulnerable people extremely unwell.
Alice Casey, the UHB's chief operating officer, said that, while norovirus is extremely common in the community at this time of year, it can present problems when it spreads in hospitals.
"Many people will have the norovirus bug at this time of year - we see it every year and, for most people, it will be unpleasant but not serious.
"But when norovirus spreads in hospitals, where patients are already unwell and are in close proximity to each other on wards, the effects can be more serious.
"At this stage, we're asking people to be sensible and to stay away from the hospital if they possibly can, to avoid spreading the bug.
"In addition, it may be that you've had norovirus yourself and are feeling a bit better and think it's safe to come in and visit. The reality is that there needs to have been at least 48 hours since your symptoms cleared before you can be confident that you're not going to spread the bug to someone else.
"We know that it's difficult when people have friends and relatives in hospital and they naturally want to pop in and visit. Over the coming weeks, we're asking for the public's help in helping us to limit the spread of norovirus so that we can protect vulnerable patients from the effects of this nasty bug by staying away from the hospital."
She advised people with a sickness bug, or family members suffering from one, to visit the NHS Direct website or the NHS Choices website for information.