, and shortness of breath. On arrival at the emergency department of Mount Sinai Hospital, on the same afternoon as symptom onset (hospital day 1), his temperature was 39·4°C, blood pressure 142/80 mm Hg, heart rate 130 beats per min, and respiratory rate20 breaths per min. Oxygen saturation ranged from 89% to 99% at ambient air. On examination, he appeared acutely ill and in mild distress with normal breath sounds. Plasmalyte (2 L), v