Figure 9. Replication and shedding of SARS-CoV-2 occur in the nasal multiciliated cells during the early stage of COVID-19.

(A) UMAP plots showing changes of normalized mRNA expression levels of SARS-CoV-2 N in total clustered epithelial cells on the indicated days of hospitalization. (B) Violin plots depicting proportion of SARS-CoV-2 genes among total detected genes per cell in each cell cluster on the indicated days of hospitalization. (C and D) Representative images showing a rapid reduction in signal intensity and number of SARS-CoV-2 NP in multiciliated cells (yellow arrowheads) during the hospitalization. Dashed box regions are magnified in lower panels or insets. Scale bars: 20 μm (C); 200 μm (D). Similar findings were observed in 6 patients with COVID-19. (E) Changes in the number of SARS-CoV-2 NP⁺ cells per 10³ smeared cells in 6 patients with COVID-19 on the indicated days of hospitalization or after symptom onset.