Which stage of pertussis is characterized by the paroxysmal cough with the characteristic 'whoop' sound and post-tussive vomiting?

Explanation

## Stages of Pertussis **Key Point:** Pertussis (*Bordetella pertussis* infection) progresses through three distinct clinical stages, each with characteristic features and variable duration. ### Clinical Stages Timeline ```mermaid flowchart TD A[Pertussis Infection]:::outcome --> B[Catarrhal Stage<br/>1-2 weeks]:::action B --> C[Paroxysmal Stage<br/>2-8 weeks or longer]:::action C --> D[Convalescent Stage<br/>Weeks to months]:::action E[Characteristic Features]:::decision B -.->|Mild URI symptoms| F[Rhinorrhea, sneezing<br/>Low-grade fever<br/>Mild cough<br/>Highly infectious]:::outcome C -.->|Severe cough| G[Paroxysmal cough<br/>Inspiratory whoop<br/>Post-tussive vomiting<br/>Apnea in infants]:::outcome D -.->|Recovery| H[Cough gradually decreases<br/>Complications resolve<br/>Immunity develops]:::outcome ``` ### Paroxysmal Stage Details | Feature | Description | |---------|-------------| | **Duration** | 2–8 weeks (can extend to 12 weeks or longer) | | **Cough pattern** | Rapid series of 5–15 coughs without inspiration | | **Whoop sound** | High-pitched inspiratory stridor after cough paroxysm (absent in infants) | | **Post-tussive vomiting** | Occurs in 50–90% of cases; can lead to malnutrition | | **Apnea** | Common in infants <6 months; may be life-threatening | | **Conjunctival petechiae** | From increased intrathoracic pressure during cough | | **Incontinence** | Older children may have stress incontinence from severe cough | **Mnemonic:** **"WHOOP"** = **W**hooping cough in **H**igh-paroxysmal stage, **O**ften with **O**pen mouth, **P**ost-tussive vomiting ### Catarrhal Stage (Often Missed) **High-Yield:** The catarrhal stage is easily mistaken for a common cold — mild URI symptoms, low-grade fever, minimal cough. This is when the organism is most easily transmitted but diagnosis is hardest. By the time the characteristic whoop appears (paroxysmal stage), the patient is often less infectious. **Clinical Pearl:** Infants <6 months may NOT develop the characteristic whoop; instead, they present with apneic spells, feeding difficulty, and respiratory distress — this is why pertussis is particularly dangerous in this age group. [cite:Park 26e Ch 33]