Bronchiolitis is a common respiratory infection that primarily affects infants and young children. It is usually caused by a viral infection, most often the respiratory syncytial virus (RSV). The condition leads to inflammation and congestion in the small airways of the lungs, known as bronchioles, making it difficult for the child to breathe. Symptoms of bronchiolitis include a runny nose, cough, wheezing, and difficulty breathing. Most cases are mild and can be managed at home, but some children may require medical attention, especially if they show signs of severe breathing difficulties or dehydration.