Differential Diagnosis for Prolonged Cough, Running Nose, and Fever

Single Most Likely Diagnosis

• Viral Upper Respiratory Tract Infection (URTI): This is the most common cause of cough, running nose, and fever, especially when symptoms persist for over a month. The prolonged duration could be due to a viral infection that has led to a secondary bacterial infection or a post-viral cough.

Other Likely Diagnoses

• Allergic Rhinitis: Symptoms such as running nose and cough can be persistent in allergic rhinitis, especially if exposure to allergens continues. Fever is less common but can occur, particularly if there's a secondary infection.
• Sinusitis: Both acute and chronic sinusitis can present with cough, running nose, and fever. The chronic form is more likely to present with prolonged symptoms.
• Influenza or Other Respiratory Viruses with Secondary Bacterial Infection: In some cases, influenza or other respiratory viruses can lead to secondary bacterial infections, prolonging the duration of symptoms.

Do Not Miss Diagnoses

• Tuberculosis (TB): Although less common, TB is a critical diagnosis not to miss due to its significant public health implications and the need for specific treatment. It can present with chronic cough, fever, and other respiratory symptoms.
• Lymphoma or Other Malignancies: Certain cancers, like lymphoma, can present with prolonged fever, cough, and other systemic symptoms. Early diagnosis is crucial for treatment outcomes.
• Immunodeficiency: Conditions that impair the immune system, such as HIV/AIDS, can lead to prolonged and recurrent infections, including those causing cough, running nose, and fever.

Rare Diagnoses

• Sarcoidosis: A systemic disease that can affect the lungs and present with cough, among other symptoms. It's less common but should be considered in the differential diagnosis of chronic respiratory symptoms.
• Histoplasmosis or Other Fungal Infections: In endemic areas, fungal infections can cause chronic respiratory symptoms, including cough and fever.
• Cystic Fibrosis (in adults with no previous diagnosis): Although typically diagnosed in childhood, some cases of cystic fibrosis may not be diagnosed until adulthood, presenting with chronic respiratory infections and other symptoms.