At the time of arrival, the patient had no subjective dyspnea under 4 L/min oxygen flow via nasal cannula, but the respiratory rate was over 30 times per minute. Chest radiographs demonstrated rapidly aggravated bilateral infiltration. Routine blood tests found white blood cell (WBC) count at 3.53 × 103/µL, with lymphopenia of 0.4 × 103/µL. C-reactive protein (CRP) and lactic dehydrogenase (LDH) elevated up to 59.7 mg/L and 814 IU/L. Routine chemistry, electrolyte, and blood coagulation tests revealed no abnormalities except mildly elevated aspartate transaminase. The level of interleukin 6 (IL-6) was increased as 101.3 pg/mL. Serial bacterial culture and polymerase chain reaction (PCR) for other respiratory viruses were all negative.