The Department of Health has estimated that 17,000 people in Northern Ireland could die in a bird flu epidemic.
Avian flu has been confined to the Far East
Dr Brian Smyth, of the Communicable Diseases Centre, said a pandemic could be caused if the avian flu mixes with more easily spread forms of influenza.
So far confined to the Far East, Dr Smyth said the conditions were ripe for an outbreak in several countries.
"The real gobal concern at the minute is if this bird flu mixes with human types of influenza," he said.
Dr Smyth said such a virus would be much more contagious that the Sars outbreak of 2003.
"It is a much more infectious virus and we know that unlike Sars, flu can be transmitted by coughs and sneezes but as well by the airborne route, just by breathing in and out," he said.
"So, if this bird flu virus does change its nature to allow it to spread from person to person then it will cause much much, more illness."
Most of those who have died have had intensive exposure to poultry, but some have not. Avian flu has developed the ability to spread from one human to another.
The government has been looking at the worst case scenarios including school closures, banning large gatherings and Dr Lorraine Doherty of the Department of Health said closing the border with the Republic of Ireland had not been ruled out.
"We haven't put in arrangements at this point in time for closing down borders," she said.
Control measures could be brought in
Anti-viral drugs would be used to fight the pandemic.
While available on private prescription, Dr Jenny McGaughey of the Royal College of General Practitioners said it would not be necessary for people to obtain their own supply, but that they would be prioritised.
"It will be important that those most at risk get the supplies initially, so we're talking about giving the supplies to people with serious other health problems," she said.
The Department of Health says that it will have a stockpile of such drugs.
But it is believed that it will only be enough for about a quarter of the population.
In the first instance they will be given to prioritised groups including health workers, the emergency services and people ill with chest or heart conditions.
Dr Doherty said people not on priority groups should not worry.
"We will give people information on their own personal control measures as it becomes appropriate to do so," he said.
"At the moment, we have no avian flu in Northern Ireland, nor is there a circulating pandemic virus in Northern Ireland so there is no need for anybody to be applying personal protective measures.
"When it becomes appropriate for us to give specific control advice we will do so."