The Chief Medical Officer has blamed Christmas socialising for the third wave of Covid-19.
Dr Tony Holohan warned that we must take action now to curb the spread of the virus, which saw a record 1,718 cases recorded on Wednesday.
Speaking after Ireland entered its third full lockdown overnight, he said: "We eased restrictions at the beginning of December after the second surge that the country experienced.
"We know that a substantial amount of activity took place in the days and weeks following that easing of restrictions.
"We know that the average number of contacts, that in each case we've identified, has increased sharply to levels that we haven't seen since the beginning of this pandemic.
"We engaged in a large amount of social activity across society which really provided this opportunity for the virus to transmit at the kind of levels we're now seeing."
Dr Holohan said it is 'vital' to stop the high level of transmission in order to keep schools open and hospital figures as low as possible.
And he warned that every member of society has a part to play in the coming months.
"Do not leave home, other than for essential reasons", he told RTE's Morning Ireland.
"For essential retail, for essential work if you can't work from home, and for exercise within 5km of your home.
"Everybody, as much as possible, observe that, and we know we can break these cycles of infection, which is currently unsustainable."
Dr Holohan said that the current spread is travelling into older age groups much faster compared to the second wave.
He added that updates on the vaccine distribution will be made available to the public, but warned that it will be months before it is fully given out, and that everyone must continue to follow advice.
