Seasonal influenza viruses are subjected to strong selection as seen by the sequential replacement of existing viral populations on the emergence of new antigenic variants. However, the process of within-host de novo mutant generation and evolutionary selection that underlies these antigenic sweeps is poorly understood. Here, we investigate mutational patterns between evolutionarily closely related human seasonal influenza viruses using host age as a proxy for immune experience.
Avian and swine influenza viruses circulate worldwide and pose threats to both animal and human health. The design of global surveillance strategies is hindered by information gaps on the geospatial variation in virus emergence potential and existing surveillance efforts.