A 6-month-old infant from rural Maharashtra presents with a 2-week history of paroxysmal cough with inspiratory stridor and post-tussive vomiting. The mother reports that an older sibling had similar symptoms 3 weeks ago. On examination, the infant is afebrile with mild respiratory distress. A nasopharyngeal swab for PCR is positive for Bordetella pertussis. The infant has received only one dose of pentavalent vaccine. What is the most appropriate immediate management?

Explanation

## Clinical Scenario Analysis This is a confirmed pertussis case in an unimmunized 6-month-old with clinical features of the paroxysmal stage (paroxysmal cough, inspiratory stridor, post-tussive vomiting). The sibling's similar illness 3 weeks prior suggests household transmission. ## Management Priorities in Pertussis **Key Point:** In infants <6 months, pertussis carries high risk of severe disease (apnea, seizures, encephalopathy, secondary bacterial pneumonia) and requires hospitalization for monitoring and supportive care. **High-Yield:** Antibiotic therapy in pertussis: - **Azithromycin** is the drug of choice (5 mg/kg/day for 5 days) - Most effective when given in the catarrhal or early paroxysmal stage - Eradicates bacteria from nasopharynx, reducing transmission - Does not significantly shorten cough duration in late paroxysmal stage but prevents complications and transmission **Clinical Pearl:** Post-tussive vomiting in an infant with pertussis is a sign of severe disease; these infants often require hospitalization for: - Continuous pulse oximetry monitoring - Nutritional support (frequent small feeds or NG feeding) - Oxygen supplementation if SpO₂ <90% - Apnea monitoring (risk of sudden apnea in infants <6 months) ## Prophylaxis for Contacts **Key Point:** All household contacts (especially unimmunized or partially immunized children) must receive azithromycin prophylaxis (single dose 5 mg/kg or 5-day course) to prevent secondary cases. | Aspect | Details | |--------|----------| | **Indication for prophylaxis** | All household contacts, especially <7 years or unimmunized | | **Drug** | Azithromycin (preferred) or clarithromycin | | **Timing** | Within 21 days of symptom onset in index case | | **Efficacy** | ~80% reduction in secondary attack rate | **Mnemonic:** **AAAA** for Azithromycin in pertussis: - **A**ntibacterial (eradicates nasopharyngeal carriage) - **A**dmit (infants <6 months) - **A**ll contacts (prophylaxis) - **A**void delay (early catarrhal/paroxysmal stage) ## Why Admission is Mandatory 1. Infant is <6 months old (highest risk group) 2. Already showing signs of respiratory distress 3. Risk of apnea, secondary pneumonia, seizures 4. Requires supportive care and monitoring --- ## Correct Answer Justification Azithromycin initiation + admission + contact prophylaxis addresses all three critical management pillars: treating the index case, preventing complications through monitoring, and breaking transmission chain.