FIGURE 1.

Ultrastructure of coronavirus particles in autopsy samples. Formalin-fixed and paraffin embedded autopsy olfactory mucosa, re-embedded for electron microscopy (a–c), and conventionally embedded autopsy lung of COVID-19 patients (d). Coronavirus (CV) particles can be identified due to a high number of similar particles that together fulfil all essential structural criteria [5]. Membrane compartments with multiple or single enclosed CV particles (white arrows), ribonucleoprotein (electron dense, partly granular structure: black arrows), surface projections (“spikes”: white arrowheads) and biomembrane (black arrowheads). See Krasemann et al. [5] for further information on the specimens and detailed recommendations for sample processing and virus identification. Entirely digitised sections and regions of these samples are online available for pan-and-zoom analysis, allowing for training of finding virus particles in autopsy samples (www.nanotomy.org) [5].