The present invention includes compositions and methods related to the structure and function of the cellular polyadenylation and specificity factor 30 (CPSF30) binding site on the surface of the influenza A non-structural protein 1 (NS1). Specifically, critical biochemical reagents, conditions for crystallization and NMR analysis, assays, and general processes are described for (i) discovering, designing, and optimizing small molecule inhibitors of influenza A (avian flu) viruses and (ii) creating attenuated influenza virus strains suitable for avian and human flu vaccine development.