Abstract
We introduce and discuss a minimal individual based model for influenza dynamics. The model takes into account the effects of specific immunization against viral strains, but also infectivity randomness and the presence of a short lived strain-transcending immunity recently suggested in the literature. We show by simulations that the resulting model exhibits substitution of viral strains along the years, but that their divergence remains bounded. We also show that dropping any of these features results in a drastically different behaviour, leading either to the extinction of the disease, to the proliferation of the viral strains or to their divergence.