This thesis should be read as an almost chronological account of the clinical problems we faced and subsequently investigated while we were treating the waves of COVID-19 patients in real-time. It combines multiple original investigations, narrative reviews, book chapters and research letters concerning the diagnosis, risk stratification, monitoring and complications of COVID-19 patients in the acute and critical care setting during the emerging and developing pandemic, with a special emphasis on the role of point-of-care ultrasound (POCUS). The thesis is divided into three main parts. Part 1 focuses on the use of conventional tests at the emergency department (ED) in the diagnosis and prognosis of COVID-19, as well as its complications. Part 2 explores how POCUS might aid in this setting. Part 3 addresses how POCUS might aid in monitoring of the disease course in critically ill COVID-19 patients. And how it might help diagnose COVID-19 complications in this setting.