The Mater hospital in Dublin has restricted visits due to an outbreak of norovirus, also known as the winter vomiting virus.
Visitors are asked not to visit patients unless absolutely necessary.
All children and anyone who has suffered nausea, vomiting or diarrhea or been in contact with anyone experiencing these symptoms over the past 72 hours are asked to stay away from the hospital.
People who believe they may have the winter vomiting virus are asked to attend their GP rather than the hospital's A&E department.
In recent weeks, a number of hospitals have placed similar restrictions on visitors due to outbreaks of the winter vomiting virus.
They included St Vincent's, Beaumont, Tallaght hospital, Naas General Hospital, the Mid-Western Regional Hospital in Ennis and the Midlands Regional Hospital in Mullingar.