The Midlands Regional Hospital in Tullamore, Co Offaly, has been hit by an outbreak of the winter vomiting bug.
At least seven people at the hospital are suspected of having the winter vomiting bug, or Norovirus.
Symptoms include a sudden onset of vomiting and diarrhoea. The illness is usually mild, lasting only about two days. However, it can be serious for the elderly or people ill with other conditions.
The Health Service Executive has asked members of the public, particularly children who are more susceptible to the virus, to stay away from the hospital unless it is vital to attend.
Anyone in the area who has experienced vomiting, nausea or diarrhoea in the past two days is advised to stay at home, drink plenty of fluids and limit contact with others. If symptoms persist, they should consult their GP.
Last March, 17 hospitals across the State recorded outbreaks of Norovirus, which normally occurs where there are large concentrations of people in close quarters. Between 1 and 3 per cent of the population are affected in a normal year.
There is no specific treatment for the illness, and, as it is viral, antibiotics have no effect.