Members of the public are being asked to stay away from Cork University Hospital after a recent increase of cases of the winter vomiting bug.
In a statement the HSE has asked people to minimise their visits - either to the Emergency Department or to see patients.
It says measures to control the outbreak have been implemented within the hospital.
Meanwhile, the ED continues to be extremely busy - from Friday until Sunday 502 patients presented to the Emergency Department, 162 of which required in-patient admission.