Viral upper respiratory tract infection (URTI): This is the most common cause of cough in children, often presenting with other symptoms like runny nose, sore throat, and fever. The high frequency of viral infections in this age group makes it the most likely diagnosis.

Asthma: A chronic condition that can cause cough, especially at night or with exercise, often accompanied by wheezing and shortness of breath. Asthma is common in children and can be triggered by viral infections.
Allergic rhinitis: Allergies can cause a chronic cough, along with symptoms like sneezing, runny nose, and itchy eyes. This is more likely if the child has a history of allergies or if the cough is seasonal.
Pertussis (Whooping Cough): Although vaccination has reduced its incidence, pertussis can still occur, especially if vaccination is incomplete or waning. It's characterized by a distinctive whoop sound during coughing fits.
Bronchitis: Either acute or chronic, bronchitis can cause a cough, often productive of mucus, and may follow a viral infection.

Pneumonia: Bacterial or viral pneumonia can present with cough, fever, and difficulty breathing. It's crucial to diagnose and treat promptly to avoid complications.
Foreign body aspiration: This is an emergency, especially in young children, but can occur in older children as well. Symptoms can include sudden onset of cough, choking, or difficulty breathing.
Tuberculosis (TB): Although less common in many parts of the world, TB can cause a chronic cough, weight loss, and fever. It's essential to consider, especially if the child has been exposed to someone with TB.
Cystic Fibrosis: A genetic disorder that leads to persistent lung infections and cough. Other symptoms include poor growth, greasy stools, and recurrent pneumonia.

Habit cough: A psychological condition where the cough is a habit and not due to any underlying disease. It's usually dry and can be suggestive if it occurs only in certain situations.
Gastroesophageal reflux disease (GERD): Can cause a chronic cough, especially after eating or at night, due to stomach acid irritating the throat.
Bronchiectasis: A condition where parts of the airways are damaged, leading to chronic cough and recurrent infections. It's less common but should be considered if there's a history of severe infections or underlying conditions like cystic fibrosis.
Interstitial lung disease: A broad category of diseases affecting the lung tissue, which can cause cough, difficulty breathing, and other symptoms. These are rare in children but can occur.