A definitional diagnosis of cough and fever involves identifying the most likely underlying condition based on clinical features, history, and associated symptoms. Both cough and fever are nonspecific symptoms seen in a variety of diseases, and the diagnosis often depends on the context. Below is a general framework:
### Infectious causes (common)
1. Upper respiratory tract infections (URTIs):
- Examples: Viral rhinitis, pharyngitis, or laryngitis.
- Clues: Sore throat, runny nose, mild fever.
2. Lower respiratory tract infections:
- Bronchitis: Productive cough, mild to moderate fever.
- Pneumonia: Fever, chills, productive cough, chest pain, dyspnea.
- Tuberculosis (TB): Chronic cough, low-grade fever, night sweats, weight loss.
3. COVID-19 or influenza:
- Clues: Dry cough, high fever, fatigue, muscle aches, loss of taste/smell (COVID-specific).
4. Pertussis (whooping cough):
- Clues: Paroxysmal coughing fits, inspiratory whoop, post-tussive vomiting.
5. Fungal infections (e.g., histoplasmosis, coccidioidomycosis):
- Clues: Common in immunocompromised patients or endemic areas.
### Noninfectious causes
1. Asthma exacerbation:
- Cough worse at night, wheezing, triggered by allergens or infections.
2. Chronic obstructive pulmonary disease (COPD) exacerbation:
- Productive cough, low-grade fever, dyspnea, smoking history.
3. Allergic conditions:
- Postnasal drip causing cough, afebrile.
4. Pulmonary embolism:
- Sudden onset of cough (sometimes with blood-tinged sputum), low-grade fever, chest pain, dyspnea.
5. Cancer (lung cancer or metastases):
- Persistent cough, low-grade fever, weight loss, hemoptysis.
6. Heart failure:
- Cough (often nocturnal), low-grade fever (due to pulmonary congestion), dyspnea.
### Other systemic causes
1. Autoimmune diseases (e.g., sarcoidosis, lupus):
- Chronic cough, low-grade fever, systemic symptoms.
2. Gastroesophageal reflux disease (GERD):
- Chronic cough, worse when lying down, no fever.
3. Drug-induced fever and cough:
- Example: ACE inhibitors causing dry cough.
### Key factors to guide diagnosis:
- Onset and duration (acute vs. chronic).
- Type of cough (dry vs. productive).
- Associated symptoms (dyspnea, sputum color, hemoptysis, weight loss, night sweats).
- Exposure history (travel, occupational exposure, smoking, pets).
- Underlying conditions (e.g., immunosuppression, asthma, GERD).
Further diagnostic workup often includes:
- Physical exam.
- Chest X-ray or CT scan.
- Blood tests (e.g., WBC, CRP, cultures).
- Sputum analysis.
- Pulmonary function tests.