A man with pre-existing health conditions has contracted the coronavirus having never travelled to one of the hot zones abroad such as northern Italy.
The case, in Co Cork, is thought to be the first in the country of community spread of the virus and came as the number of confirmed cases in Ireland jumped last night by seven to 13.
It has also emerged a GP who has been struck down with the virus may have exposed hundreds of patients to the infection after he continued to work after returning from northern Italy.
It's understood two of yesterday's newly identified cases, announced at a briefing by the Department of Health, are linked to the GP and his family in the west.
The GP from north Clare, whose wife and two children have also been diagnosed with the virus, carried out normal practice surgery on several days, out-of-hours duty and also did a shift in a busy hospital emergency department.
It is understood he also treated patients in a nursing home.
The four positive tests on Wednesday sparked an urgent hunt by public health doctors for patients who could have been exposed to the virus after the doctor became infectious.
The parents, their daughter and son are being treated in a hospital in the west of Ireland.
It is understood that while all are positive, it is just one of the children who has symptoms.
Of the seven new cases identified yesterday, four are travel-related from northern Italy, four males from the east of the country.
Two schools -a primary and secondary 10km apart - have been shut until March 18 and pupils have been told to restrict their movements. A number of children in a third school were also asked to go into isolation.
The doctor also did a shift in a west of Ireland hospital emergency department last week with a high number of patients on trolleys.
An emergency meeting took place at the hospital yesterday and student doctors were told to urgently self-isolate until March 12.
Following news of the positive test on Wednesday night, protocols were implemented and a section of the emergency department was closed.
A room or facility where a person who has tested positive for the virus has been disinfected. Patients were transferred out of the unit to allow for the cleaning.
Ambulance staff were informed not to transport patients to the emergency department while the cleaning was under way. Parents were yesterday coming to terms with the worrying news.
A text to parents said: "A person in your school has tested positive for novel coronavirus (Covid-19).
"As a precaution, the school will be closed until March 18. The Department of Public Health HSE Mid-West will be in contact with you tomorrow with further information.
"This is the text the HSE has asked to have sent out to all parents and staff."
In a follow-up message to parents yesterday, they were asked to come and pick up textbooks this morning and tomorrow up to lunchtime.
"Take care and we will keep you posted," it said.
The third school, also a second level institution, was closed by school management pending advice from the HSE.
A handwritten sign on the front door of the school yesterday said it would "remain closed today pending advice from the HSE re: Covid-19 virus".
One parent of a child attending the primary school said: "We all got a text tonight confirming that a child in the school had been confirmed as testing positive for the virus.
"We really don't know what to do now. There's been a lot of talk on the parent's WhatsApp group and we haven't a clue what will happen next.
"My child is off school for the next two weeks, which means I'll have to stay at home and take time off my job. That's going to be very, very tough.
"I can't really ask someone else to mind him in case he has picked it up. I don't know what do."
The father of a secondary school student said: "The worrying thing is all the talk and rumours."