Differential Diagnosis for a 5-Month-Old with Fever and Cough

Single Most Likely Diagnosis

• Viral Upper Respiratory Tract Infection (URTI): This is the most common cause of fever and cough in infants, often caused by viruses such as rhinovirus, coronavirus, or respiratory syncytial virus (RSV). The age of the patient and the presentation of fever and cough are typical for a viral URTI.

Other Likely Diagnoses

• Bronchiolitis: Common in infants, especially those under 2 years old, bronchiolitis is usually caused by RSV and presents with cough, fever, and sometimes wheezing.
• Pneumonia: Can be caused by viral or bacterial pathogens, presenting with fever, cough, and possibly difficulty breathing. The clinical presentation and risk factors (such as exposure to someone with pneumonia) would guide the suspicion towards this diagnosis.
• Influenza: Although more common in older children and adults, influenza can affect infants and presents with fever, cough, and possibly other systemic symptoms like lethargy or poor feeding.

Do Not Miss Diagnoses

• Bacterial Pneumonia: While less common than viral causes, bacterial pneumonia (e.g., caused by Streptococcus pneumoniae, Haemophilus influenzae type b, though less common due to vaccination) is a critical diagnosis to consider due to its potential severity and need for antibiotic treatment.
• Pertussis (Whooping Cough): Especially in areas with low vaccination rates or in infants too young to be fully vaccinated, pertussis can present with severe coughing fits and is a significant concern due to its contagiousness and potential for severe complications.
• Sepsis: Although rare, sepsis is a life-threatening condition that can present with non-specific symptoms including fever and cough, especially in very young infants whose immune systems are not fully developed.

Rare Diagnoses

• Tuberculosis (TB): Uncommon in infants in many parts of the world but critical to consider, especially with exposure history (e.g., family member with TB), as it requires specific treatment and public health measures.
• Congenital Anomalies: Certain congenital heart diseases or anatomical abnormalities of the airways can present with recurrent or persistent respiratory symptoms, including cough and fever.
• Immunodeficiency: Infants with underlying immunodeficiencies may be more susceptible to unusual or severe infections, presenting with recurrent or persistent fever and cough.