AT1, AT2, AT2 cells, AT2 organoids, COVID-19 distal lung disease, COVID-19 pneumonia, COVID-19-associated pneumonia, FACS-purified ITGA6 + ITGB4 + basal cells, ITGA6, ITGA6 + ITGB4 + mitotic population, ITGB4, KRT5 +, KRT5 + basal cells, SARS, SARS-CoV, SARS-CoV-2, SARS-CoV-2 receptor ACE2, TNFRSF12A, TNFRSF12A + cells, TNFRSF12A hi subfraction, basal and AT2 apical, basal cell, basal cell organoids, basal organoid KRT5 + cells, cancer, clonogenic, club and ciliated cells, club cells, distal human lung progenitors, feeder-free organoid culture, human, human distal lung alveolar and basal stem cells, human distal lung stem cell, in vitro human distal lung culture systems, in vitro organoid model, interstitial lung disease, long-term human distal lung organoid cultures, lung infectious diseases, mouse, progenitor, single adult human alveolar epithelial type II, slowly proliferating, slowly proliferating human tissue