Figure 2.

A schematic diagram demonstrating the evolution of the four stages of COVID-19 symptoms. The first stage is asymptomatic, but the majority of the relatively rare cases who are asymptomatic on the date of identification went on to develop disease. Approximately 80% of laboratory confirmed patients had mild-to-moderate disease (Second stage) with typical signs and symptoms including fever, dry cough, fatigue, sputum production, shortness of breath, sore throat, and headache. Approximately 15% have severe disease (Third stage), manifested as severe pneumonia and acute respiratory distress syndrome. Approximately 5–6% are critical (Fourth stage), characterized by respiratory failure, septic shock and/or multiorgan failure.