A common clinical cause of chronic bronchitis in children is infection. Infection: infection by pathogenic microorganisms such as viruses and mycoplasma is a common clinical cause of chronic bronchitis. Common pathogenic microorganisms include adenovirus, respiratory syncytial virus, Mycoplasma pneumoniae infection. Early lesions of chronic bronchitis are located in the small airways. When the virus deposits can cause airway narrowing and obstruction as well as bronchial inflammatory changes, mucus gland secretion increases, the ciliated epithelium is damaged or destroyed to varying degrees, so that sputum is difficult to discharge, trapped in the bronchial tubes, affecting ventilation. If a child develops cough, sputum, wheezing, etc., it is recommended to take the child to the respiratory department of the hospital as soon as possible to clarify the cause of the disease, and then treat the cause of the disease.