Main Points: Bronchiolitis is a common respiratory tract infection in infants and young children. It is usually caused by a viral infection, most commonly RSV. Symptoms include difficulty breathing, wheezing, and coughing. Bronchiolitis is often self-limiting but can be severe in some cases. Comparison with Asthma: Bronchiolitis is primarily caused by a viral infection, while asthma is a chronic condition. Both conditions involve inflammation of the airways, but the underlying causes are different. Pathophysiology: The virus infects the nasopharyngeal mucosa and spreads to the lower airways. Inflammation and mucus production lead to narrowing of the bronchioles. Gas exchange is impaired due to decreased airflow. Symptoms arise from inflammation, mucus plugging, and atelectasis. Clinical Features: Nasal discharge Nasal congestion Wheezing Cough Difficulty breathing Fever (in some cases) Diagnosis: Based on clinical symptoms and physical examination. Chest X-ray may show hyperinflation and peribronchial cuffing. Treatment: Supportive care, including hydration and oxygen therapy. Medications may be used to treat symptoms.