ABSTRACT
A detailed understanding of the pathophysiologic mechanisms of severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2) infection and Coronavirus disease 2019 (COVID-19) is vital for improving patient management - to facilitate prompt recognition of progression to severe disease and effective therapeutic strategies. This chapter summarizes the underlyingpathophysiology in the lungs and other organs of COVID- 19 patients. The roles of the cytokine storm culminating in exaggerated inflammatory responses and formation of neutrophil extracellular traps (NETs) are discussed. Pathological features of the various stages from the onset of COVID-19 are outlined - progressing from early mild infection to severe clinical illness to the critically ill phase. © 2023 by World Scientific Publishing Co. Pte. Ltd.