Michael McBride said a grown-up had indicated a possible positive outcome for Covid-19, and the analysis was being checked by research centers in England.
Health authorities are now trying to establish what contacts the patient had in Ireland since travelling from Italy.
Dr Adrian Mairs, Acting Director of Public Health at the Public Health Agency (PHA), added: "Northern Ireland has well-prepared and rigorously-tested plans for dealing with infectious diseases, and these have been activated".
The Department of Health confirmed: "Contact tracing is now completed". More than 400 individuals have been contaminated with the infection in Italy, and 12 individuals have passed on, with the nation now thought about the focal point of the infection in Europe.
Dr Holohan said the passenger followed the correct protocol and informed health authorities of her symptoms.
Deputy chief medical officer Dr Ronan Glynn said: "If it's necessary to give more information in a particular instance we are more than willing to do that, and we have done that for things like measles, but there was no need to do that in this instance".
He said those with casual passing contact should not be concerned.
He said the Health Service Executive in the Republic of Ireland will be contacting people who sat within two rows of the person on the plane from northern Italy to Dublin.
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Reacting to the draw, Ismael, per lask.at , said: " Manchester United is one of the best teams in the world". The Swiss government has banned all events involving more than 1,000 people until at least March 15.
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.
A case of coronavirus has been confirmed in Northern Ireland.
'We have robust infection control measures in place which enable us to respond immediately.
The woman, who is a healthcare worker living in Belfast, had travelled with a child on an Aer Lingus flight from northern Italy to Dublin before making her way north.
The general public is advised to follow advice from the HSE and the HPSC to protect their health.
Covid-19 is spread through close contact with an infected person's body fluids, such as droplets from coughing or sneezing, or by touching surfaces that an infected person has coughed or sneezed on.
The main signs of infection are fever, coughs and shortness of breath or breathing difficulties.
The affected areas are mainland China, South Korea, Japan, Singapore, Hong Kong, Iran and four regions in northern Italy.