Differential Diagnosis and Management for a 3-Month-Old with Dry Cough, Vomiting, Fever, and Excessive Crying
Most Likely Diagnosis
This 3-month-old most likely has viral bronchiolitis, and as a peripheral medical practitioner, you should provide supportive care only—no medications are indicated at this stage. 1, 2
Differential Diagnosis
The key differentials for this presentation include:
Viral bronchiolitis (most common): Respiratory syncytial virus (RSV) is the leading cause in infants under 2 years, presenting with upper respiratory prodrome (rhinorrhea, low-grade fever) followed by lower respiratory symptoms (cough, wheezing, increased respiratory effort) 3, 4, 2
Pneumonia: Must be considered given the fever and cough, though dry cough without respiratory distress signs makes bacterial pneumonia less likely 3
Pertussis: The combination of paroxysmal cough with post-tussive vomiting in a 3-month-old (potentially incomplete vaccination) warrants consideration 3, 1, 5
Urinary tract infection (UTI): Accounts for over 90% of serious bacterial infections in febrile infants 2-12 months old, occurring in 8-13% of young febrile infants, and can present with nonspecific symptoms including fever, vomiting, and irritability 5, 6
Viral upper respiratory tract infection with post-nasal drip: Can cause dry cough and vomiting from coughing paroxysms 1
Critical Assessment Required
You must perform a focused physical examination looking for:
Respiratory rate: Count for full 60 seconds (most accurate method); tachypnea is defined as ≥60 breaths/min in infants <2 months old 3, 5
Signs of respiratory distress: Nasal flaring, subcostal retractions, grunting, chest indrawing, accessory muscle use 3, 7
Oxygen saturation: <92% at sea level indicates need for hospital admission 7
Chest examination: Listen for wheezing, crackles, decreased breath sounds, or hyperinflation (loss of cardiac dullness on percussion, liver pushed below 6th intercostal space, Hoover sign) 3, 7
Hydration status: Assess feeding ability, urine output, mucous membranes, fontanelle 3, 2
Toxic appearance: Altered consciousness, severe lethargy, signs of shock 6
Diagnostic Testing Recommendations
For a 3-month-old with fever and respiratory symptoms:
Chest X-ray should be obtained if any signs of acute respiratory illness are present (respiratory distress, abnormal auscultation, chest indrawing) 3, 5
Urinalysis and urine culture should be obtained in all febrile infants 3-12 months old, as UTI is the most common serious bacterial infection 5, 6
Do NOT routinely order: Complete blood count, blood cultures, or viral testing unless the child appears more than mildly ill or has specific indications 3, 5, 7
Treatment as a Peripheral Medical Practitioner
Supportive care ONLY—no medications are indicated:
What TO DO:
Maintain hydration: Continue breastfeeding or formula feeding; if unable to maintain oral hydration, refer for IV/nasogastric fluids 1, 2
Saline nasal drops: Use to relieve nasal congestion and facilitate feeding 1
Elevate head of bed: Improves comfort and breathing during sleep 1
Minimize environmental irritants: Especially tobacco smoke exposure 1
Supplemental oxygen: If oxygen saturation <92%, provide oxygen and arrange immediate transfer 2, 7
What NOT TO DO:
Do NOT prescribe over-the-counter cough and cold medications: No efficacy and risk of serious adverse events in children under 6 years 1
Do NOT prescribe codeine-containing medications: Risk of serious side effects including respiratory distress 1
Do NOT prescribe antibiotics empirically: A dry cough with clear breath sounds in an infant is consistent with viral infection and does not warrant antibiotics 1, 4
Do NOT prescribe bronchodilators (albuterol, epinephrine): Not recommended in infants 1-23 months with bronchiolitis 3, 4, 2
Do NOT prescribe corticosteroids: Not useful in bronchiolitis 4, 2
Do NOT prescribe asthma medications: Unless other features of asthma are present (recurrent wheeze, dyspnea) 1
Expected Clinical Course
Most viral-associated coughs resolve within 7-10 days, with 90% of children cough-free by day 21 1
Bronchiolitis symptoms typically worsen for several days before resolving over days to weeks 4, 2
Immediate Referral Criteria (RED FLAGS)
Refer immediately to hospital if ANY of the following develop:
- Respiratory distress (grunting, severe retractions, nasal flaring) 1, 6
- Oxygen saturation <92% 1, 7
- Inability to feed or signs of dehydration 1, 2
- Altered consciousness or severe lethargy 6
- Cyanosis 3
- Age <3 months with any respiratory distress 3
Follow-Up Instructions
Instruct parents to return immediately if:
- Cough becomes paroxysmal with post-tussive vomiting or inspiratory "whoop" (suggests pertussis) 1, 5
- Fever persists ≥5 days 6
- Respiratory symptoms worsen 1
- Child develops petechial or purpuric rash 6
Routine follow-up:
- If symptoms persist beyond 4 weeks with dry cough and no other symptoms, continue watchful waiting as most resolve spontaneously 1
- If cough becomes wet/productive after 4 weeks, initiate 2-week course of antibiotics targeting common respiratory bacteria 1
Common Pitfalls to Avoid
- Over-diagnosing asthma in infants with isolated dry cough or wheezing from bronchiolitis 1
- Prescribing empirical antibiotics without evidence of bacterial infection 1, 4
- Using chest X-rays routinely when clinical diagnosis of bronchiolitis is clear 3, 7
- Missing UTI as a cause of fever in this age group—always obtain urinalysis 5, 6
- Missing pertussis in incompletely vaccinated infants with paroxysmal cough and vomiting 3, 1, 5
Parent Education
- Explain this is likely a self-limited viral illness resolving in 7-10 days 1
- Emphasize that no medication is needed or beneficial—supportive care is the appropriate evidence-based approach 1
- Provide clear instructions on warning signs requiring immediate return 1, 6
- Emphasize hand hygiene and avoiding contact with sick individuals 1