Whooping Cough Transmission: How Pertussis Spreads and Prevention

Bordetella pertussis spreads via respiratory droplets; high secondary attack rates (80% in susceptible households). Understanding transmission informs control.

Transmission Dynamics

• Portal: Cough/sneeze → aerosolized droplets (large + small).
• Infectious Period: Catarrhal (1–2 weeks, non-specific) → paroxysmal (2–8 weeks). Most contagious early; antibiotics shorten to 5 days.
• Incubation: 5–10 days (range 4–21).
• R₀: 12–17 (highly contagious; measles-level).

Clinical Stages

1. Catarrhal: Rhinorrhea, mild cough, low-grade fever. Highly infectious.
2. Paroxysmal: Staccato cough → inspiratory "whoop" (infants/children), post-tussive emesis, cyanosis.
3. Convalescent: Gradual resolution over weeks; cough recurs with URI.

High-Risk Groups

• Infants <3 months (apnea, pneumonia, encephalopathy, death).
• Pregnant women (3rd trimester) → fetal transmission risk.
• Immunocompromised, chronic lung disease.

Prevention Layers

• Vaccination: DTaP series, Tdap booster, maternal Tdap (cornerstone).
• Source Control: Mask if symptomatic; isolate until 5 days of antibiotics.
• Hygiene: Handwashing, surface disinfection (survives hours on fomites).
• Post-Exposure Prophylaxis: Azithromycin for all household/high-risk contacts regardless of vaccination.

Public Health Response

• Mandatory reporting; contact tracing.
• School/childcare exclusion until 5 days antibiotics or 21 days cough onset.
• Outbreak threshold: 2+ epi-linked cases → enhanced surveillance.

Pertussis is vaccine-preventable but not vaccine-eliminated with current tools. Maternal immunization remains the single most impactful intervention for infant protection.