Question 1 of 166
A 4-month-old, previously healthy, full-term infant is brought to the clinic in January with 3 days of copious clear rhinorrhea, cough, low-grade fever, and increased work of breathing. On exam, temperature is 38.1°C (100.6°F), respiratory rate 58/min, and oxygen saturation 95% on room air. There is mild subcostal retraction, diffuse bilateral wheezes, and fine end-expiratory crackles. The infant is feeding at about two-thirds of normal and remains well-hydrated and interactive. Which of the following is the most likely diagnosis?