Norovirus is an extremely common bug, which is not normally dangerous.
Cardiff and Vale University Health Board has warned that "the effects can be more serious" for ill and vulnerable patients.
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.
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. 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.
– Alice Casey, Chief Operating Officer, Cardiff and Vale University Health Board