South Tipperary General Hospital in Clonmel has imposed a visitor ban over a vomiting bug outbreak.
A visiting ban will be in place over the coming days, and only the critically ill will be allowed to receive visitors.
A total of 16 patients are described as being "active" in terms of displaying symptoms consistent with the Noro Virus and another four patients are described as "contact" cases.
Arrangements at the hospital will be reviewed on a daily basis, and the Health Service Executive (HSE)has requested the general public's co-operation to ensure infection control measures are successful.
The HSE has recommended that anyone who has experienced vomiting and/or diarrhoea, should avoid visiting any hospital or nursing home until they are symptom-free for 72 hours.