The COVID-19 pandemic resulted in nearly 140 million people becoming infected with the SARS-COV-2 virus in the US from March of 2020 through July of 2023. The result was an influx in acutely and critically ill patients being treated in the hospital, advanced utilization of oxygen and life support devices, and prolonged lengths of hospitalizations. With variations in clinical presentation across the timespan of the pandemic, the COVID-19 pandemic seems to be a moving target for rehabilitation therapists to understand the needs of these patients both acutely and chronically. This course, in part one of two, will discuss the pathophysiology of variants of COVID-19, the acute presentation of ARDS and the acute-on-chronic presentation of COVID Fibrosis, with related medical and rehabilitation considerations. Case studies relating to each presentation will be discussed along the way including medical presentation, pharmacology, and laboratory markers as well as treatment strategies for each phase of illness.