Suspected cases: a comprehensive analysis is conducted based on epidemiological history and clinical manifestations. Cases that meet any one condition of the epidemiological histories and have any two conditions of the clinical manifestations. If there is no clear history of epidemiology, then the case should meet three conditions of the clinical manifestations.

History of Epidemiology:

1) Travel or residence history in Wuhan and its surrounding areas or other communities with reported cases within 14 days before the onset of the disease.

2) History of contact with COVID-19 infected patients (the result of nucleic acid test is positive) within 14 days before the onset of the disease.

3) Contact with patients with fever or respiratory symptoms from Wuhan and its surrounding areas or other communities with reported cases within 14 days before the onset of the disease.

4) Cluster infection: within 2 weeks, 2 or more cases of fever and/or respiratory symptoms occurred in small areas such as homes, offices, and school classes.

Clinical manifestations:

1) Fever and / or respiratory symptoms;

2) Having the imaging features of COVID-19: multiple patchy shadows and interstitial changes are found in the early stage, especially in the lung periphery. And then the conditions develop into multiple ground-glass opacities (GGO) and infiltration shadows. Severe cases may develop consolidation of lung tissue, with incidence of hydrothorax being rare;

3) The total leukocyte count is normal or decrease, or the lymphocyte count is normal or decrease in the early stage of the disease.

Confirmed case: suspected case with one of the following etiology or serological evidences:

1) The result of RT-PCR used to detect the nucleic acid of COVID-19 is positive;

2) The result of virus gene sequencing analysis is highly homologous with the known COVID-19.

3) Serum IgM antibodies and IgG antibodies to COVID-19 are positive; serum IgG antibodies to COVID-19 turn from negative to positive or the IgG antibody titers of recovery period are 4 times or more higher than that of acute phase.

Asymptomatic infection: those who have no clinical symptoms, positive for COVID-19 tests of their respiratory tract specimens or serum-specific IgM antibodies to COVID-19. It is mainly found through close contact screening, cluster infection investigation and source trace investigation.

(Reference: Prevention and control of COVID-19 (Sixth Edition) issued by National Health Commission; Diagnosis and Treatment Protocol for COVID-19 (Trial Version 7) issued by the General Office of the National Health Commission and the Office of the National Administration of Traditional Chinese Medicine)

Source: Chinese Center for Disease Control and Prevention