The article analyses different stages of COVID-19 pathogenesis that drive development of severe complications, including acute respiratory distress syndrome, multiple organ failure and endotoxicosis. COVID-19 progression is described, from the first moments of infection to the disruption of the alveolar-capillary barrier and acute respiratory distress syndrome. The article looks at the causes initiating pathological processes that lead to acute respiratory distress syndrome. The special focus is on oxidative stress, hyperreactivity of the immune system, endothelial dysfunction, and cytotoxic effects of the virus. The article discusses tentative treatments for COVID-19 at different stages of its pathogenesis.