Seven more patients have been diagnosed with the so-called winter vomiting bug at St Vincent's University Hospital in Dublin in the past 24 hours.
The hospital said there have been 199 cases to date, of which 24 are currently symptomatic.
In addition, some 136 staff members at the hospital have also been hit by the bug and about half of those are on sick leave.
In a statement, the hospital said: "Despite the hospital taking all the necessary precautions to curtail the spread of this highly contagious virus, practically all ward areas are affected, including parts of the Emergency Department. This is having an impact on bed allocation and admissions through the Emergency Department."
St Vincent's appealed to members of the public not to attend the A&E department if they were merely complaining of the effects of the virus as it can spread to other, more seriously ill, patients.
The hospital has also asked the public to avoid visiting patients at the hospital where possible.