Acute Bronchitis: This is the most likely diagnosis given the symptoms of upper respiratory infection with thick yellow sputum, runny nose, and pharyngeal pain. Acute bronchitis is a common condition characterized by inflammation of the bronchial tubes, often caused by a viral infection, and can lead to the production of thick, discolored sputum.

Common Cold (Rhinovirus Infection): The common cold is a viral infection that affects the upper respiratory system, causing symptoms such as a runny nose, sneezing, and pharyngeal pain. While it typically does not produce thick yellow sputum, some cases can lead to secondary bacterial infections that might result in such symptoms.
Influenza: Influenza, or the flu, is another viral infection that can cause upper respiratory symptoms, including a runny nose, cough (which might produce yellow sputum), and sore throat. The presence of systemic symptoms like fever and body aches can help differentiate it from other diagnoses.
Sinusitis: Sinusitis, an inflammation or infection of the sinus cavities, can present with similar symptoms, including thick yellow or green nasal discharge, facial pain, and cough. It often follows a viral upper respiratory infection.

Pneumonia: Although less likely than the above diagnoses, pneumonia is a critical condition that requires prompt diagnosis and treatment. It can present with cough, fever, and production of thick, yellow or green sputum. Bacterial pneumonia, in particular, is a concern and can be life-threatening if not treated appropriately.
Epiglottitis: This is a rare but potentially life-threatening condition involving inflammation of the epiglottis, which can cause severe sore throat, difficulty swallowing, and shortness of breath. It requires immediate medical attention.
Pertussis (Whooping Cough): Pertussis is a highly contagious bacterial infection that can cause severe coughing fits, often accompanied by a characteristic "whoop" sound, and can lead to production of thick mucus. It's particularly dangerous in infants and young children.

Tuberculosis (TB): TB is a bacterial infection that primarily affects the lungs but can spread to other parts of the body. It can cause chronic cough, production of thick, discolored sputum, and other systemic symptoms. TB is less common in many parts of the world but remains a significant concern in areas with high prevalence or in individuals with specific risk factors.
Cystic Fibrosis: This is a genetic disorder that leads to the production of thick, sticky mucus that can clog the airways and trap bacteria, resulting in recurrent respiratory infections, lung damage, and other complications. It's typically diagnosed in childhood but can be considered in adults with recurrent or severe respiratory symptoms.
Bronchiectasis: A condition characterized by damage to the airways, leading to their widening and scarring, which can result in chronic cough, production of thick sputum, and recurrent infections. It can be a complication of various conditions, including infections, autoimmune disorders, and cystic fibrosis.