a, NPA specimens of two patients with COVID-19 were used to inoculate one droplet of bat enteroids (Bat-ERD_NPA B) or one droplet of human enteroids (Hu-ERD_NPA A). Cell-free media (n = 1) were harvested at the indicated hours after inoculation and followed by detection of viral gene copy. The data show the results of one specimen. b, The media of the last timepoints of inoculated bat enteroids (Bat-ERDm) or human enteroids (Hu-ERDm) were used for the second round of inoculation in one droplet of human enteroids. Viral gene copies were detected in cell-free media (n = 1). c, The human enteroids in the second round of inoculation and mock-inoculated enteroids were fixed and subjected to immunostaining of viral NP (green). Nuclei and actin filaments were counterstained with DAPI (blue) and Phalloidin-647 (purple), respectively. Scale bar, 10 µm. d, Undifferentiated (unDFR) human enteroids and differentiated (DRF) enteroids of the same line were subjected to RT–qPCR to detect the transcriptional level of ACE2, TMPRSS2 and CTSL. Data represent the mean and s.d. of a representative experiment, n = 3. Independent experiments were performed three times. Two-tailed Student’s t-test. The differentiated human enteroids were subjected to immunofluorescence staining to label human ACE2 and TMPRSS2 protein (green). To explicitly show ACE2 expressed on cell surface membrane, the channel of actin is not incorporated into the image. The organoids stained with the second antibody only are imaged as a control (Ctrl). Scale bar, 10 µm. Images are representatives of at least five similar images.