3.1. Clinical manifestations
Based on the current epidemiological investigation, the incubation period of the COVID-19 is about 1-14 days(Linton et al., 2020a). The main manifestations are fever, dry cough and fatigue and some patients had nasal congestion, runny nose, myalgia and diarrhea(Linton et al., 2020b). According to the severity of symptoms, COVID-19 can be divided into four classes: mild, moderate, severe, and critical(Zu et al., 2020). Mild patients only presented low-grade fever, mild fatigue or dry cough only. Moderate always characterized by fever, respiratory symptoms, and radiographic features. The severe patients should meet one of these criteria: A. dyspnea B. PaO2/FiO2<300 mmHg. C. Oxygen saturation <93% in ambient air (Z. Sun, Thilakavathy, Kumar, He, & Liu, 2020). And about half of the patients may develop into critical patients with acute respiratory distress syndrome, septic shock, and coagulation dysfunction within a week(Gorbalenya, 2020). According to the recent survey conducted by China CDC, 80.9% of the confirmed patients (44672) were mild pneumonia cases, 13.8% were severe cases, and 4.7% were critical cases. It had been revealed that the fatality rate of critical patients was 49%(Wang, Wang, Chen, & Qin, 2020). Patients with basic diseases such as chronic respiratory disease, cardiovascular disease, diabetes, cancers, would developed into ARDS and worsened in a short period of time even died of multiple organ failure and have a higher case fatality rates than those without. Current reported data revealed that 86.6% of confirmed patients were aged 30-79 years and 1-2% of the patients were children and newborns (1.5 months to 17 years), and most of whom had a close contact with infected cases or were family cluster cases. In fact, Infected children might appear asymptomatic or present with fever, dry cough, and fatigue, and few presented with gastrointestinal symptoms including abdominal discomfort, nausea, vomiting, abdominal pain, and diarrhea(Shen et al., 2020). Most of them recovered within 1–2 weeks after disease onset. In general, children always presented with relatively mild symptoms and have a good prognosis(J. F.-W. Chan, Yuan, Kok, To, Chu, Yang, Xing, Liu, Yip, & Poon, 2020). The clinical course of pregnant women with the COVID-19 is similar to patients of the same age.