
Those in close contact with a woman diagnosed with Covid-19 have been traced and notified, health authorities in Ireland said.
She had flown from northern Italy to Dublin Airport before continuing her journey by land, reportedly using public transport.
It is understood she has been treated at home.
Irish health chief Dr John Cuddihy said: "Each of the stages of this person's journey have been identified and all relevant contacts in all of those stages of transport have been contacted (and) traced."
People who sat within two rows of the person on the plane from northern Italy to Dublin were contacted.
The woman followed advice in reporting concerns to a GP and "self-isolated" at home whilst awaiting the results of testing.
Ireland's Chief Medical Officer, Dr Tony Holohan, and the head of the Health Protection Surveillance Centre, Dr Cuddihy, held a news conference in Dublin to provide details of Ireland's preparedness.
Dr Holohan said they were depending on an individual with symptoms travelling back from an affected area identifying themselves, contacting the local health authorities, and that was what had happened in this particular case.
Public health protocols, similar to those used to respond to previous incidents of pandemic influenza, Sars and Mers, have been in place since January and are operating effectively, the officials added.
The positive result has been sent to Public Health England laboratories for verification.
A special unit has been established at the Royal Victoria Hospital in Belfast for isolating those suffering from the virus but the health authorities were unable to confirm where the individual is being treated.
Ireland's Health Minister, Simon Harris, said it was "not unexpected" and is to meet staff at Dublin Airport activating the public awareness campaign for Covid-19 on Friday morning.
The Republic's National Public Health Emergency Team has been planning for this scenario since January.
The minister said the public should continue to adhere to public health protocols issued by the Department of Health.
The patient travelled to Northern Ireland via Dublin after coming from northern Italy in the last 48 hours.
Other plane passengers, who did not sit next to the woman, have been contacted and told while they do not need to self isolate they should monitor themselves for possible symptoms.
Independent.ie understands that passengers sitting in close proximity, rows in front, back and adjacent will be kept under surveillance.
Other passengers and crew are also to be monitored and efforts are being made to contact train passengers.
Sources said work on contacting people who may have been in contact with the patient are “going well”.
“The system is working very well,” a source said, adding: “People need to understand this is a virus that we must contained – but we could be dealing with it until the end of the year. It’s not going to pass quickly.”
Speaking at the press briefing, Chief Medical Officer for Northern Ireland Dr Michael McBride said the person was not part of a school trip.
Dr McBride said that one person has confirmed to have the virus and that a second test is being done in England for a second confirmation. The first test was a "presumptive positive test" for the virus.
He said the person did not attend their general practice and self-isolated. He said he is confident that the PHA and the health service are "on top" of dealing with the case.
An isolation ward has also been put in place at the Royal Victoria Hospital in Belfast.
The National Public Health Emergency Team said they are aware of the presumptive case of COVID-19 and that Public Health Authorities have activated contact tracing protocols.
Health Minister Simon Harris said the first case on the island "was not unexpected" and that officials had been planning for this scenario since January.
“The general public should continue to adhere to the public health protocols issued by the Department of Health," he said.
Dr Tony Holohan, Chief Medical Officer in the Dept of Health, said: “The HSE is well-prepared and is working to inform any contacts the patient had in order to prevent transmission.”
“COVID-19 is spread through close contact with an infected person’s body fluids (e.g. droplets from coughing or sneezing), or by touching surfaces that an infected person has coughed or sneezed on.
“Close contact involves either face to face contact or spending more than 15 minutes within 2 metres of an infected person. The risk of transmission through casual contact is low.”
Speaking on RTE’s evening news bulletin this evening, Dr Holohan said: “This is not a surprise. We’ve been prepared for this eventuality.”
He said the passenger followed the correct protocol and informed health authorities that he or she had symptoms, he said.
“This individual came forward, identified they had symptoms and liaised with us.”
As for fellow passengers aboard the as-yet unidentified flight, he said the airline involved has the passenger manifest that would be handed over to health officials.
Passengers sitting within two rows of the affected passenger are being contacted this evening by health officials, he said.
But he said operations at the airport will remain as normal.
“It doesn’t give us cause for surprise,” he said. “Nothing has changed.”
Any person concerned that they may have symptoms of COVID-19 should immediately isolate themselves from others and phone their GP.
Earlier today, the HSE said the coronavirus may already be circulating in Ireland but it has not been picked up on tests so far.
HSE public health officials said the fear is that someone who has it will delay seeking medical care.
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There is the potential for more people being infected by that person during the time lag.
This would mirror the crisis in parts of north Italy where hundreds of people have tested positive in the last week.
The HSE also conceded there is a risk of an outbreak in overcrowded hospitals which continue to battle the trolley crisis.
Suspect cases who need to be brought to hospital for a swab test can no longer be routinely brought by ambulance.
They will have to arrange their own transport with a relative.
This is because of the rising number of suspect cases due to more countries being added to the at risk list.
Use of an ambulance would take from the delivery of other routine care.
However, using people’s own transport to take them to hospital for a swab also increases the chance of passing on the infection if the prove positive.
The HSE briefing was told that around 2,000 queries were received by the HSE helpline over the past week about the coronavirus and some 300 were referred to public health staff.
Adequate stocks of protective equipment and clothing which are essential for health staff are available despite difficulties in procuring the items.
Meanwhile, the organisers of the St Patrick’s Day Festival said today they will take “a measured and proportionate response” to the public health threat from the new coronavirus.
The spread of the virus to countries which will be sending participants to the festival has raised questions about it going ahead.
In a statement today, the organisers said that following detailed meetings yesterday with the Department of Transport, Tourism and Sport, it has been confirmed to St Patrick’s Festival that the National Public Health Emergency Team has established an expert sub-group to develop criteria for the risk assessment of mass gatherings.
This criteria is expected to be made available early next week.
Globally, Denmark was among those countries confirming their first cases on Thursday, while Saudi Arabia has stopped Muslim pilgrims entering to worship at the holy cities of Mecca and Medina.
In Japan, all schools will close for several weeks, while US experts have reported the first case of unknown origin, which suggests the virus is spreading there.
In China, where the virus originated, 78,497 cases have been reported, including 2,744 deaths.
After Brazil confirmed Latin America's first case on Wednesday, the virus has reached every continent except Antarctica.
World Health Organisation (WHO) director-general, Dr Tedros Ghebreyesus, told a press conference in Geneva on Thursday that coronavirus has the potential to become a global pandemic but this stage had not been reached.
Public health advice remains to wash hands with soap, not rub the face and maintain a distance from people who are coughing and sneezing, he said.
Dr Michael Ryan, executive director of the WHO Health Emergencies Programme, said the idea that the virus is mostly being transmitted by people without symptoms is a "myth".
He added: "Data from China does not suggest that asymptomatic people are becoming the driving force behind this."