KRT5 and swine influenza: Zuo et al. elucidated a group of distal airway basal stem cells of Krt5+p63+ (distal airway stem cells, DASCs), which give rise to collections of Krt5+ basal cells (or pods) in severely damaged areas of H1N1 influenza-injured mouse lungs and then proliferate and differentiate and participate in alveolar repair and regeneration [25, 31, 32].