Microscopic observations of SARS‐CoV‐2 like particles in different oral samples

The emerging coronavirus pneumonia epidemic caused by the SARS‐CoV‐2 infection has spread rapidly around the world. The main routes of transmission of SARS‐CoV‐2 are currently recognised as aerosol/droplet inhalation. However, the involvement of the oral cavity in coronavirus disease 2019 (COVID‐19) is poorly known. The current data indicates the presence of viral RNA in oral samples, suggesting the implication of saliva in SARS‐CoV‐2 transmission, however, no direct observation of SARS‐CoV‐2 particles in different oral samples has been reported. In this study, we investigated whether particles of SARS‐CoV‐2 were present in oral samples collected from three symptomatic COVID‐19 patients. Using scanning electron microscopy (SEM), the correlative strategy of light microscopy and electron microscopy and immunofluorescence staining, we showed the presence of SARS‐like particles in RT‐qPCR SARS‐CoV‐2‐positive saliva, dental plaque and gingival crevicular fluid (GCF) samples. In the saliva samples, we demonstrated the presence of epithelial oral cells with morphogenetic features of SARS‐CoV‐2 infected cells. Inside those cells, vacuoles filled with nascent particles were observed, suggesting the potential infection and replication of SARS‐CoV‐2 in oral tissues. Our results corroborate previous studies and confirm that the oral cavity may be a potential niche for SARS‐CoV‐2 infection and a potential source of transmission.