Varicella & Pertussis

A child's rash starts on the trunk with lesions in every stage at once, while another child has been coughing for three weeks and just turned blue. Two diseases, two very different isolation protocols.

Varicella (chickenpox) presents with a hallmark rash that erupts first on the trunk, then spreads to the face and extremities. The defining feature is lesions in all stages simultaneously — macules, papules, vesicles, and crusts on the same body area. The rash is intensely pruritic. The child is contagious from 1–2 days before the rash appears until all lesions have crusted over (typically 5–7 days). Varicella requires strict airborne plus contact precautions because the virus spreads via aerosolized particles (true airborne transmission) and direct vesicle contact. Aspirin is absolutely contraindicated due to the risk of Reye syndrome. Pertussis (whooping cough) progresses through three stages: catarrhal (1–2 weeks of mild URI symptoms — the most contagious phase), paroxysmal (severe coughing fits ending with an inspiratory "whoop," often with post-tussive vomiting and cyanosis), and convalescent (gradual recovery over weeks to months). Infants may not whoop — they present with apnea instead. Pertussis requires droplet precautions and is treated with macrolide antibiotics (azithromycin or erythromycin). Close contacts receive post-exposure prophylaxis with the same macrolides regardless of vaccination status.

Key Distinctions

Don't confuse varicella's airborne-plus-contact isolation with pertussis's droplet precautions — varicella is airborne, pertussis is not. Students mix up varicella's multi-stage simultaneous rash with smallpox, which progresses uniformly (all lesions same stage). The catarrhal stage of pertussis looks like a common cold but is the most contagious phase — by the time the whoop appears, the child has been spreading the disease for weeks.

Clinical Pearl

Varicella: all stages at once, airborne room, never aspirin. Pertussis: the whoop gets attention, but the cold stage spreads the disease.