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Smallpox
🌍 About
- Smallpox was officially eradicated in 1979 following a WHO-led global vaccination campaign.
- Edward Jenner developed the first vaccine using cowpox virus (basis of modern immunisation).
🦠 Aetiology
- Variola major: Severe, mortality ~30%.
- Variola minor: Milder, mortality ~1%.
- Incubation: 7–17 days (patients not contagious in this period).
🩺 Clinical Presentation
- Key Diagnostic Feature: Lesions involve palms and soles (chickenpox usually spares).
- Lesions: All at the same stage of development in a given area (unlike chickenpox).
- Stages of Illness:
- Prodrome (2–4 days): Fever, severe headache, backache, malaise, sometimes vomiting. Occasionally contagious.
- Early Rash (4 days): 🔴 Highly contagious. Rash begins in the mouth → spreads to face → trunk and limbs. Lesions: macules → papules → vesicles → pustules. Classic central umbilication ("bellybutton").
- Pustular Rash (5 days): Contagious. Firm, round pustules with defined edges.
- Pustules + Scabs (5 days): Still contagious. Pustules crust into scabs.
- Scab Fall-Off: Contagious until last scab falls. Leaves pitted scars.
🧪 Diagnosis
- Clinical: Classic rash pattern + palms/soles involvement.
- Laboratory: PCR for variola DNA (only in specialised reference labs).
⚕️ Management
- Isolation: Immediate, strict infection control.
- Supportive care: Fluids, analgesia, fever control. No specific antiviral routinely available.
- Vaccination post-exposure: Within 3–4 days can prevent or reduce severity.
- Contact tracing & ring vaccination: Essential to halt outbreaks.
⚠️ Complications
- Encephalitis
- Keratitis → corneal scarring → blindness
- Pneumonia
- Secondary bacterial infection of skin lesions
🛡️ Prevention & Control
- Routine vaccination stopped after eradication; stockpiles retained for emergencies.
- High vigilance required due to bioterrorism threat (Category A agent).
- Containment strategy: rapid isolation, ring vaccination, strict PPE for healthcare staff.
📊 Comparison: Smallpox vs Chickenpox
| Feature | Smallpox | Chickenpox |
|---|---|---|
| Distribution | Face, extremities (incl. palms/soles) | Trunk > face, rarely palms/soles |
| Lesion stages | All at same stage in area | Different stages (macule + vesicle + crust together) |
| Fever | High, precedes rash | Mild, concurrent with rash |
| Scarring | Common (pitted scars) | Uncommon |
| The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms. |
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