Early detection of SARS-CoV-2 in circulating immune cells in a mouse model.

SARS-CoV-2 infects the respiratory tract, lung and then other organs. However, its pathogenesis remains largely unknown. We used RareScopeâ"¢ Fluorescence Light Sheet Microscopy (FLSM) and fluorescent in situ hybridization of RNA (RNA-FISH) to detect SARS-CoV-2 RNA and dissemination kinetics in mouse blood circulation. By RNA-FISH, we found that SARS-CoV-2 RNA-positive leukocytes, including CD11c cells, appeared as early as one day after infection and continued through day 10 post infection. Our data suggest that SARS-CoV-2-permissive leukocytes contribute to systemic viral dissemination, and RNA-FISH combined with FLSM can be utilized as a sensitive tool for SARS-CoV-2 detection in blood specimens.