A 68-year-old woman was admitted to the hospital with fever, progressive dyspnea, and cough productive of white sputum. The patient's history included type 2 diabetes mellitus, hypertension, and obesity. She had a 2-pack-year history of smoking and had quit 7years earlier. Her only regular medication was metformin. On physical examination, her temperature was 37.2°C, heart rate 110 beats per minute, blood pressure 151/80mmHg, and oxygen saturation 86% while she was breathing ambient air. A cardiac examination showed tachycardia with an irregular rhythm, and bibasilar crackles were noted on lung examination.