Viral upper respiratory tract infection (URTI): This is the most common cause of cough in children, often presenting with other symptoms like runny nose, sneezing, and fever. The high frequency of viral infections in this age group due to exposure in school or daycare settings makes this diagnosis highly probable.

Asthma: A common chronic condition in children that can cause cough, especially if it's persistent and accompanied by wheezing or shortness of breath. Asthma can be triggered by viral infections, allergens, or irritants.
Allergic rhinitis: Allergies to dust mites, pollen, or pet dander can cause chronic cough, along with symptoms like sneezing, runny nose, and itchy eyes.
Pertussis (Whooping Cough): Although vaccination has reduced its incidence, pertussis can still occur, especially in areas with low vaccination rates. It's characterized by a distinctive whoop sound during coughing fits.
Bronchiolitis: Commonly caused by the respiratory syncytial virus (RSV), this condition typically affects younger children but can occur in five-year-olds, especially if they have underlying health conditions.

Pneumonia: Bacterial pneumonia can present with cough, fever, and difficulty breathing. It's crucial to diagnose and treat promptly to prevent complications.
Foreign body aspiration: Children often put objects in their mouths, and aspiration can lead to coughing, choking, or difficulty breathing. This is a medical emergency.
Tuberculosis (TB): Although less common in developed countries, TB can cause chronic cough, fever, and weight loss. It's essential to consider TB in children who have been exposed to someone with the disease or have traveled to areas with high TB prevalence.
Cystic Fibrosis: A genetic disorder that can cause chronic cough, recurrent lung infections, and failure to thrive. Early diagnosis is critical for managing the condition.

Ciliary dyskinesia (Kartagener syndrome): A rare genetic disorder affecting the cilia in the respiratory tract, leading to chronic cough, sinusitis, and bronchiectasis.
Gastroesophageal reflux disease (GERD): Can cause cough in children, especially if they have symptoms like heartburn or vomiting.
Habit cough: A psychogenic cough that can be persistent and disruptive but typically does not occur at night.
Fungal infections: Such as histoplasmosis or coccidioidomycosis, which can cause cough and are more common in specific geographic areas or in immunocompromised children.