Video report by ITV News Political Correspondent Carl Dinnen
People in Ireland have been asked to "reduce social interactions as much as possible" as it was announced all schools, colleges and childcare facilities in will close for more than a fortnight as a result of the .
Making the live announcement during his visit to Washington DC, Irish premier Leo Varadkar said the measures would take effect from 6pm on Thursday until March 29.
Teaching will be done online or remotely, he said, but public transport will continue to operate.
His announcement comes a day after the Republic of Ireland recorded its first coronavirus death.
As of 11 March, there were 43 confirmed cases in the country.
The Taoiseach said many more people in Ireland would get the virus and would get sick.
"Unfortunately we must face the tragic reality that some people will die," he said.
State-run "cultural institutions" will also close and indoor gatherings of more than 100 people and outdoor meetings of more than 500 will be cancelled.
Dublin's annual St Patrick’s Day parade was cancelled earlier this week over fears about coronavirus.
Mr Varadkar said acting as one nation could save lives and that the economy will suffer, but "we can bounce back".
"We are a great nation and we have overcome many trials in the past with our determination, and we will prevail again," Mr Varadkar said.
He said the Government had a duty to protect those at risk categories of people, such as older people and those with underlying conditions.
“We have not witnessed a pandemic of this nature in living memory and this is uncharted territory for us,” he said.
“We said we would take the right actions at the right time and we have to move now to have the greatest impact.”
The Taoiseach is in Washington DC to meet President Donald Trump as part what should be the annual St Patrick's Day programme of events but which have been largely cancelled this year in light of the pandemic.
Irish deputy premier Simon Coveney said the radical measures will be a lot for the Irish public to take in.
"We are asking Irish people to stay apart," he said.
"The days and weeks ahead will be difficult and the government cannot do this on its own.
"The most effective tool is to do everything we can to slow down the spread. Those who are vulnerable are precious.
"It will have a deep impact on people's abilities to do their job.
"We are asking people to continue to work where possible. Those who go to the places of work should limit contact."
Mr Coveney asked people to be "calm" adding they were measures the government had been planning for "some time".
Northern Ireland is following the UK's plan to delay the spread of coronavirus by encouraging self-isolation for anyone who feels unwell and have not ordered the closure of schools.
Stormont First Minister Arlene Fostersaid she had no prior notice of what the Irish Government was going to shut schools.
Deputy First Minister Michelle O'Neill defended the decision not to close schools in Northern Ireland.
"This is a very confusing day. People are anxious as to why it is a good idea in the south (but not in Northern Ireland).
"We are working together, we are being guided by the medical science."We don't believe at this minute in time that that is the right step to take.
"Inevitably we will get to the situation where we need to consider closing schools."
Measures brought in by the Irish government:
Individuals who have symptoms should self-isolate for a period of 14 days.
Individuals should reduce discretionary social contacts as much as possible.
Elderly and/or medically vulnerable people should reduce as much as possible contacts outside home.
There should be no mass gatherings involving more than 100 people if located indoors, or involving more than 500 people if located outdoors.
Closure of museums, galleries and tourism sites.
Closure to students of schools, creches, other childcare facilities and higher education institutions.
Reduction of workplace contacts, and implementation of remote working practices and teleconferencing where possible and not to travel for meetings. Work time and break times should be staggered, where possible.
Restriction of visiting at hospitals, long-term care settings, mental health facilities, prisons, and spacing measures in homeless shelters.
Coronavirus: Everything you need to know