Pulmonary Structure and the Way of Infection, the Clinical Course and Risk Factors of Serious Condition in COVID-19

SARS-CoV-2 invades a host cell through angiotensin-converting enzyme 2 (ACE2) receptor, and infection is established. A symptom such as a cold develops, but a digestive organ symptom, taste disorder and sense of smell disorder are seen. A latency period is 1-14 days (the most frequent is 5 days). Droplet infection and contact infection are the main infection course. 80% of patients are mild, and 20% of remainder needs hospitalization. Case fatality rate is 2-3%. The risk factors of the aggravation include advanced age (65 years or older), the malignant tumor, chronic obstructive pulmonary disease (COPD), chronic kidney disease, type 2 diabetes, high blood pressure, hyperlipidemia, obesity and a smoking custom. In the sex, a man is higher in the death rate than a woman. After having recovered, a variety of symptoms are prolonged, and the subsequent complications (aftereffects) are also problems.