ABSTRACT
History may repeat itself, but never quite in the same way, and thus the many lessons from the two influenza epidemics in Catalonia, Spain (Chapter 2) are instructive. My first observations are about the viruses themselves and how biomedical researchers develop knowledge about them. We know that influenza viruses are sufficiently variable for it is never clear whether an epidemic will be very important, very powerful and thus very deadly, or on the contrary, whether it will be much more limited, with relatively moderate mortality. Those in charge of predicting how an epidemic will unfold and preparing for it are now faced with this incontestable difficulty, and I believe that we are all obliged to show a certain modesty in the face of such difficult predictions.
