Smallpox: Transmission, Symptoms & Infection Process – A Comprehensive Guide

1. Initial Exposure

Smallpox spreads primarily through close contact with an infected person or by inhaling infectious respiratory droplets.

2. Incubation Period

After exposure, there is an incubation period of approximately 10–14 days before symptoms appear.

3. Onset of Symptoms

Initial symptoms resemble the flu:

• High fever
• Headache
• Muscle aches
• Back pain
• Weakness

4. Primary Rash

Within 2–4 days of the first symptoms, a rash develops, typically starting on the face and spreading to the rest of the body.

5. Evolution of Rash

The rash progresses through distinct stages:

• Macules: Flat, red spots
• Papules: Small, raised bumps
• Vesicles: Clear, fluid-filled blisters
• Pustules: Yellow, pus-filled blisters

6. Maximum Rash

The pustular rash peaks around 3–4 days after its onset.

7. Secondary Spread

Infected individuals are highly contagious from rash onset until all lesions have crusted over.

8. Lesion Progression

Pustules eventually rupture, forming scabs that dry out and crust over.

9. Scabbing and Healing

Scabs detach over several weeks, often leaving scars.

10. Duration

The infectious period lasts about 2–3 weeks, from rash onset until all lesions have crusted over.

11. Transmission Routes

Smallpox can spread through:

• Direct contact with respiratory droplets or pustules
• Indirect contact with contaminated objects (clothing, bedding)
• Airborne transmission over short distances

12. Complications

Severe cases may lead to:

• Bacterial infections
• Pneumonia
• Encephalitis (brain inflammation)
• Blindness
• Death

13. Eradication

Smallpox is one of the few diseases eradicated through global vaccination. The last natural case occurred in Somalia in 1977.