Fig 1.

Scheme of the COVID-19 diagnostic process in mainland China. In mainland China, patients with any COVID-19 symptoms and/or a documented history of contact with individuals with a confirmed case of COVID-19 were examined with CT scanning and PCR testing. Patients were then divided into 3 categories on the basis of findings in lung imaging. Signs of pneumonia in imaging and a positive PCR test result were used to diagnose and confirm COVID-19. Patients who had a contact history and typical signs of pneumonia in imaging but had a negative PCR test results were clinically diagnosed as having COVID-19 and subsequently retested with PCR and antibody assays. Before February 11, 2020, asymptomatic cases were reported as COVID-19 in mainland China. In early February, the 4th edition of Diagnosis and Treatment Protocol for Novel Coronavirus Pneumonia was released in mainland China; it recommended reporting SARS-CoV-2 infection in 2 categories: (1) COVID-19 (cases with confirmed infection and disease symptoms) and (2) asymptomatic infection. Any symptoms, including discomfort reported by patients, disease parameters measured by doctors (eg, high body temperature and low fingertip pulse oximeter reading), and signs of pneumonia in CT images, will define a case as symptomatic. The current reported COVID-19 cases in mainland China include all cases of COVID-19 (cases involving patients with infection plus symptoms) and asymptomatic cases (cases involving patients who never had symptoms) of SARS-CoV-2 infection determined before February 11, 2020.