Health service bosses appealed to members of the public today to avoid visiting hospitals if they are struck down by the winter vomiting bug.
With cases of the highly contagious virus now reported in hospitals in Cork, Kerry and Dublin, visitor restrictions have been put in place.
The Health Services Executive (HSE) for the South has appealed to the public, to refrain where possible, from visiting hospitals if they have recently been affected by the winter vomiting virus.
Gerry O'Dwyer, Hospital Network Manager in the HSE South, said: "Any person with vomiting and/or diarrhoea, or anyone who has had contact with persons with those symptoms should not visit hospital until they have been symptom free for 72 hours.
"We would appeal to the public to bear this in mind when visiting a sick relative or friend. The virus is extremely infectious and is currently very much at large in the community. Patient care is our priority and this virus can further debilitate those who are already sick in hospital."
Mr O'Dwyer asked visitors to contact any hospital or health facility if they are planning to visit to confirm if restrictions are in place.
"The virus also has the capacity to severely disrupt the day to day running of our hospitals as we have seen in the Mercy University Hospital, Cork recently," Mr O'Dwyer said.
"Elective procedures have to be rescheduled because admissions must be curtailed. Services may also be reduced if staff members are affected. We would ask visitors, therefore, to be mindful of how contagious the virus is and also thank them in advance for their co-operation and support."
The winter vomiting bug, which is also known as Small Rounded Structured Viruses (SRSV), usually causes short-lasting outbreaks of abdominal pain and nausea followed by diarrhoea and/or vomiting.
It rarely causes severe problems but can be debilitating in small children or older people who are already sick.
Mr O'Dwyer said the virus was highly infectious and could be spread by direct contact with vomit or diarrhoea; from someone who is ill; from the air around someone who has just vomited and through contaminated food.
The health service recommended people affected by the virus should drink fluids, maintain strict hygiene and avoid visiting hospitals or nursing homes.
People are advised if symptoms persist to contact a GP by telephone to explain their condition before going to a surgery.