Patients can not lie in the supine or prone position. They may have a pale complexion, cold sweat on the forehead, serious dyspnea, and a heavy cough with a large amount of white or pink foamy sputum. Rales of small, intermediate, and large bubbles are extensive in the bilateral lungs and are accompanied by the sound of boiling water. The respiratory rate is >30 breaths/min, while the heart rate is >120 beats/min and is accompanied by arrhythmia. Chest X-rays reveal asymmetric cloudy shadows covering >1/2 of the bilateral lungs, and CT scans indicate scattered or isolated alveolar edema of the terminal bronchioles. The white blood cell count is 10 × 10 9 /L.