Beaumont Hospital in Dublin is restricting visits due to an outbreak of the winter vomiting bug.
It said that one visitor only per patient per visiting period is permitted, and children are not to visit under any circumstances.
The hospital also said that its Emergency Department is under pressure due to the bug, also known as Norovirus.
The Hospital is urging people with symptoms like nausea, vomiting or diarrhoea to go to their GP first, rather than attending the emergency department.