Health chiefs have warned that the major spike in the norovirus infection, which causes violent vomiting and diarrhoea, will continue right through the festive season.
It is estimated that as many as 5,000 people a week are falling ill with the bug, which is rampant in hospitals, schools and workplaces.
Hospitals are now facing a winter vomiting epidemic over Christmas as cases have risen by 464pc in a single week.
The escalating number of cases is due to the greater number of parties and gatherings as Christmas approaches.
Dr Kevin Kelleher from the Health Protection Surveillance Centre (HPSC) said that there has been a four-fold increase in the illness this year.
Officially there were 305 cases of norovirus notified to the HSE Health Protection Surveillance Centre (HPSC) last week.
However experts say that for every recorded case there are hundreds more unreported.
The current strain, which is highly infectious, has been circulating here for the past five years, the HPSC said.
Galway and Roscommon University Hospital Group chief operating officer Tony Canavan said that there were a number of patients in the hospital with symptoms of the virus.
"There has been a surge in cases of the winter vomiting virus in recent weeks and it was always likely that we would get more cases of it in the hospital," he said.
"The hospital is under tremendous pressure and will be all winter; we simply cannot afford to lose beds because of virus outbreaks.
"We ask people not to visit if they are ill themselves or have been recently."
Britain is facing a similar crisis with reports that around 120,000 people have had the illness in the last seven days.
Yesterday the number of hospital patients left waiting on trolleys here has rocketed by a remarkable 25pc in one day.
Some 340 patients were on trolleys in hospitals around the country today, up from 274 yesterday, figures provided by the Irish Nurses and Midwives Organisation reveals (INMO).
It is unclear whether the spike is related to the winter vomiting bug.
Doctors are advising families hit by the illness to contact their local GP immediately.
Clothes and bedding that might be infected should be washed at 60C or above to kill the bug.
Hand-washing and infection control are of paramount importance, doctors said.
Professor Ian Clarke, a norovirus expert at Southampton University, UK, said festive socialising was "without question" leading to more infection.
"People with small children are going to parties, there's much more social mixing at this time of year. The opportunities for spreading increase," he said.