Detection of SARS-CoV-2 in platelets from patients with severe COVID-19. Analysis of transmission electron micrographs of platelets from patients with severe COVID-19 revealed the presence of characteristic crown-like structures reminiscent to SARS-CoV-2 particles (A). Images shown are from 3 patients and are representative of the 10 patients with severe COVID-19 analyzed. Viral-like particles were identified on the basis of specific criteria, including the size of the viral particle (100 nm ± 20%), the presence of a white halo around the particle, the size of the endosomal structure containing the viral particle (between 100 and 150 nm), and the crown-like spikes on the surface of the particle. Quantitative analysis was performed on transmission electron micrographs (186 from n = 6 healthy donors [31 for each], 160 from n = 4 septic patients without COVID-19 [40 for each], and 240 from n = 10 patients with severe COVID-19 [24 for each]). The percentage of platelets from healthy controls, patients with bacterial sepsis, and patients with severe COVID-19 containing viral-like particles was quantified (B). Results are mean ± SEM; each circle represents an individual. **P < .01; ***P < .001 according to the nonparametric Mann-Whitney test. The presence of SARS-CoV-2 Spike protein within platelets was analyzed by immunofluorescence and super-resolution confocal microscopy with the Airyscan module (C). F-actin staining using phalloidin-AF488 allowed platelet visualization. Representative images from 6 healthy donors and 6 patients are shown (bar represents 5 µm). Immunogold labeling of SARS-CoV-2 Spike (D) and nucleocapsid (E) proteins analyzed by TEM confirmed the presence of these viral proteins in platelets from patients with severe COVID-19. Representative images from 3 different patients are shown for illustration.