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, coupled with the typical presentation, makes this the single most likely diagnosis.

Asthma: A common condition in children that can cause cough, especially if it's persistent and worsens at night or with activity. Other symptoms might include wheezing and shortness of breath.
Allergic rhinitis: Allergies can cause chronic cough, along with symptoms like sneezing, runny or itchy 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: Common in younger children, especially during the winter months, caused by the respiratory syncytial virus (RSV). Symptoms include cough, wheezing, and sometimes difficulty breathing.

Pneumonia: Bacterial or viral pneumonia can present with cough and fever. It's crucial to diagnose promptly as it may require antibiotic treatment and can lead to serious complications if not addressed.
Foreign body aspiration: This is an emergency, especially in young children who might not be able to communicate effectively. Symptoms can include sudden onset of cough, choking, or difficulty breathing.
Tuberculosis (TB): Although less common in many parts of the world, TB is a critical diagnosis not to miss due to its public health implications and the need for specific treatment. It can present with chronic cough, weight loss, and fever.

Cystic Fibrosis: A genetic disorder that leads to persistent lung infections and cough, among other symptoms. It's rare but important to consider in children with recurrent respiratory infections.
Primary ciliary dyskinesia (Kartagener syndrome): A rare genetic disorder affecting the cilia, leading to chronic respiratory infections, including cough, and other systemic manifestations.
Habit cough: A rare condition where the cough is psychogenic, not related to any underlying organic cause. It's usually seen in school-aged children and can be challenging to diagnose.