SARS-CoV-2 and COVID-19: An Ultrastructural Perspective

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak is the prime cause of coronavirus disease 2019 (COVID19), a global pandemic marked by widespread respiratory illness. SARS-CoV-2, a member of the Coronaviridae family, is a highly pleomorphic virus known for its high infectivity and pathogenicity. The pandemic led to approximately 14.9 million deaths worldwide. The virus induces systemic inflammation, cardiovascular and pulmonary complications, and acute respiratory distress syndrome (ARDS), which leads to complications such as coagulopathy and cytokine storms, contributing to overall disease severity. Common COVID-19 symptoms include shortness of breath, fatigue, body aches, diarrhoea, nausea, vomiting, and flu-like symptoms, such as dry cough, sore throat, and fever. Nonspecific symptoms include headache, dizziness, sweating, chills, anosmia, chest pain, disorientation, seizures, and rashes. The leading causes of death during the pandemic were respiratory failure, septic shock, multiorgan failure, and cardiac arrest. SARS-CoV-2 primarily targets the respiratory system but also involves multiple organs. Still, its precise pathogenic mechanism remains elusive, and further research is required to unravel the interplay between viral infection and the host’s immune response. Understanding the ultrastructural perspective is essential for gaining deeper insights into SARS-CoV-2 biology and disease progression. In this chapter, the macromorphological analysis highlights the gross anatomical changes, while the histopathological observations report microscopic changes in organs and tissues from deceased COVID-19 patients. Electron microscopy (EM) provides insights into viral heterogeneity and subcellular structures that mimic the ultrastructure features of SARS-CoV-2. However, the impact of temperature on the ultrastructure of SARS-CoV-2 and its variants is not yet fully understood. The ultrastructural perspectives provide a detailed view of viral interaction with host cells, highlighting key processes such as internalization, localization, identification, and morphogenesis. This approach also elaborates the infectivity levels of SARS-CoV-2 and distinct ultrastructural changes in different systems, organs, tissues, and cells. Furthermore, the severity of COVID-19 and its correlation with viral load, tissue damage, and virion extrusion from cells are also discussed. These insights, obtained by advanced microscopy techniques, elucidate the dynamics of SARS-CoV-2 infection, viral replication, and disease progression in COVID-19.