Why are young patients with COVID 19 having strokes? Why are ventilators not as effective as expected? Why do some patients have the symptoms of altitude sickness? One explanation for these mysteries is the disease keeps adapting and changing. But the other is that our understanding of it is catching up to what might be the truth: COVID 19 is not primarily a lung disease but rather a disease of the cells that line the inside of blood vessels and lymphatic vessels. Pulmonologist Roger Seheult, one of the drivers behind the popular Medcram video series, talks about the evolving understanding of COVID 19 and his approach to explaining complex medical subjects to a general audience.