However, in human airway epithelial cultures, a higher original input of <20% double mutant genomes became enriched to approximately 50% of the virus population by 48 h post-infection demonstrating a subtle replicative advantage (Fig. 4f), also in line with the enhanced support of the mutant polymerase by human ANP32A and B proteins in the polymerase assay (Fig. 4b). Here, ANP32A is linked to infection.