Viral upper respiratory tract infection (URTI): This is the most common cause of chronic cough in children, often resulting from a viral infection that can persist for several weeks. The long duration of symptoms and the age of the child make this a likely diagnosis.

Asthma: A common condition in children that can cause chronic cough, especially if it's associated with wheezing, shortness of breath, or cough that worsens at night or with activity.
Allergic rhinitis: Allergies can cause chronic cough due to postnasal drip, and this condition is common in children.
Pertussis (whooping cough): Although less common due to vaccination, pertussis can still occur, especially if the child is not fully vaccinated or if there's a waning immunity.
Reactive airway disease: Similar to asthma but might not have all the classic symptoms of asthma, still causing cough and wheezing.

Pneumonia: Bacterial pneumonia can cause a prolonged cough, and while less likely than viral causes, missing this diagnosis could lead to severe consequences.
Tuberculosis (TB): Although rare in many areas, TB is a critical diagnosis not to miss due to its potential severity and the need for specific treatment.
Foreign body aspiration: This is an emergency that can cause cough and respiratory distress, especially if the object is lodged in the airway.
Congenital heart disease: Certain heart defects can lead to chronic cough due to pulmonary congestion.

Cystic fibrosis: A genetic disorder that leads to persistent lung infections and cough, among other symptoms.
Primary ciliary dyskinesia: A rare genetic disorder affecting the cilia in the respiratory tract, leading to chronic respiratory infections and cough.
Habit cough: A psychological condition where the cough is a habit and not due to any underlying organic cause.
Gastroesophageal reflux disease (GERD): Can cause cough due to acid reflux irritating the respiratory tract, though less common as a sole cause of chronic cough in children.