Which of the following is NOT considered an upper airway infection?

Bronchitis is classified as a lower airway infection rather than an upper airway infection. It primarily affects the bronchial tubes, which are located in the lower respiratory tract, and is characterized by inflammation of the bronchi, often leading to coughing, mucus production, and difficulty breathing. In contrast, conditions classified as upper airway infections, such as croup, epiglottitis, and diphtheria, involve the structures of the upper respiratory system, including the larynx, trachea, and pharynx. Understanding the distinction between upper and lower airway infections is crucial, as they often present with different symptoms and require varied management approaches.