This first module, written by students for students, is designed to walk you through the disease characteristics of COVID-19, including the basic virology of SARS-CoV-2 (the etiologic agent of COVID-19) and clinical knowledge to date. We hope that a deeper understanding of the pathophysiology of the virus, including its structure, transmission, and host immune defenses, will allow you to critically engage with evolving diagnosis, treatment, and prevention efforts. Throughout, we will highlight areas of ongoing investigation and innovation, from bench to bedside. We expect that this module will take 2.5-3 hours to complete.