Various strains of "Bird Flu" and "Swine Flu" are always on the "rise". The way that the Influenza virus mutates between birds, pigs, and humans presents a constant threat that a strain will emerge which causes a pandemic.
It's cyclic and inevitable.
All anyone can do is to keep a healthy immune system, get vaccinated, know some basic behaviors to keep from contracting viruses, keep a course of Tamiflu and Relenza on hand, as well as some N-95 respirators.
Have a plan. Be prepared.