COVID-19: the essential in three stages

When the first cases of COVID-19 infection started to be detected the profound difference between patients in terms of severity of disease quickly became evident. A vast majority of patients remained asymptomatic and eventually healed while some, despite lacking initial symptom, eventually worsen and a few fell ill quite rapidly. While facing a new disease, COVID-19 pneumonia was approached based on medical knowledge translated from the most similar illness but, a year later since the beginning of the outbreak in Northern Italy, knowledge has evolved. This text has the intent to offer a comprehensive view of COVID-19 pneumonia and its treatment options as a continuum of the same but complex disease, from the early to the late phase.