A 20-year-old man, with no medical history, was referred to the emergency ward because of severe shortness of breath. Heteroanamnesis revealed that he had suffered influenza-like symptoms for a week, which had become worse in the last 24 h. Physical examination showed a critically ill patient with high fever (body temperature 40°C), tachycardia (pulse rate 110/min), tachypnoea (respiratory rate...