It seems to me that the authorities - governments and international organisations - are being (correctly) more cautious than the threat requires.
All true flu viruses originate in birds and the pandemic of 1919 was extraordinarily appalling but not the last we suffered. In 1958 we experienced a much less severe pandemic in the UK and Europe.
A mutation of the current virus is required before it can be transmitted from human to human. Since that mutation has not and hopefully will not occur, it is impossible to predict the effect it will have on humans. It could be a worse case scenario as in 1919 but, hopefully, advances in viral medicine would reduce its impact. It could be like 1958 - soon forgotten because it had relatively low real impact.
However if a mutation happens and the mutated virus can be passed from one human to another, it is my view that the impact on commercial aviation to and from the quartile of the world where the mutation occurs will be totally devastating. What potential passengers will wait to see if the mutated virus causes a single death before he or she cancels his or her trip?
I am not an MD
and if any of my statements above are the slightest bit wrong I hope someone will correct me.