A secondary school in Dublin has been closed for 14 days due to concerns over coronavirus.
A male student has the virus and is being treated in a Dublin hospital with infection-control measures.
The National Public Health Emergency Team said that a risk assessment determined that "all pupils and teachers are being treated as close contacts of the confirmed case".
A woman from Northern Ireland was diagnosed with the virus on Thursday.
Two days later the first case of the coronavirus was confirmed in the Republic of Ireland.
Both had travelled home from an affected area in Italy.
Dr Tony Holohan, Ireland's chief medical officer, said "public health doctors are in direct contact with pupils, their parents and the staff involved".
While not identifying it, he said it was a "large school" and stressed "that patient confidentiality in this case, and in all cases, should be respected".
"The Department of Health will provide updated information as necessary."
'A wake-up call'
Analysis by BBC News NI health correspondent Marie-Louise Connolly
A school having to temporarily close in Dublin due to a coronavirus case is something the authorities thought they would not have to deal with so soon.
It is an indication of just how serious they are taking this individual case.
As health officials across Ireland are in regular contact and working closely together, it gives us an idea of what action would be taken here if a teacher or pupil were to be infected and had been to school and mixed with colleagues or pupils.
This move by officials in the Republic is a wake-up call for the rest of us.
The department says all pupils and teachers are being asked to restrict their movements until the end of the incubation period. This is a huge undertaking for everyone involved.
The Republic of Ireland has now just joined the growing list of countries around the world where this virus is really starting to disrupt public life.
Dr John Cuddihy, director of the Health Protection Surveillance Centre, said students and teachers at the school had been advised to restrict their movements.
The Department of Education said it was "available to assist the school in any way necessary".
"The closing of this school was a decision made on public health grounds after risk assessment deemed it appropriate. All other schools will remain open.
"The departments will continue to communicate with all schools on this issue."
The chief executive of Tourism Ireland said on Sunday he had "extremely serious" concerns over the potential impact of the virus.
Niall Gibbons said there had already been trip cancellations, amid growing fears more visitors will stay away.
Two schools in Northern Ireland have cancelled ski trips to Italy amid concerns over the coronavirus outbreak.
The decisions came after pupils and staff from three Northern Ireland schools who were recently on school trips to Italy were sent home due to coronavirus concerns.