Dermatology MCQ - Viral Infections - Smallpox

A historical public health text describes a devastating epidemic caused by a highly contagious, double-stranded DNA virus. The disease was characterized by a prodrome of high fever, malaise, and vomiting, followed by a deep-seated, monomorphic vesiculopustular rash that developed centrifugally and affected the palms and soles. Which of the following was the most critical factor in the eventual global eradication of this disease?

A) Development of a highly effective antiviral medication
B) The absence of an animal reservoir for the virus
C) The use of a stable, live-virus vaccine that conferred lifelong immunity
D) The virus's inability to form latent infections or integrate into the host genome
E) The virus's susceptibility to environmental disinfectants

Correct Answer: C) The use of a stable, live-virus vaccine that conferred lifelong immunity

This question describes smallpox, caused by the variola virus, which is the only human infectious disease to have been successfully eradicated globally.

Key Clinical Features of Smallpox:

• Prodrome: Severe febrile illness before the rash appeared.

• Rash Characteristics:

  • Monomorphic: All lesions developed and progressed at the same time (unlike chickenpox, which is pleomorphic).

  • Deep-seated and firm (vesicles were "shotty" or like pearls).

  • Centrifugal distribution: Most dense on the face and extremities, including the palms and soles.

• Outcome: Significant mortality (30% for variola major) and survivors were often left with deeply pitted scars.

The Principle of Eradication:

The global eradication of smallpox, certified in 1980, was achieved primarily due to one factor:

• The Vaccine: The live-virus vaccinia vaccine was incredibly effective.

  • It was heat-stable (crucial for use in remote, tropical areas).

  • It conferred long-lasting, durable immunity.

  • It allowed for the strategy of ring vaccination: identifying cases and vaccinating all their close contacts to create a buffer of immunity and halt transmission.

Why Not the Other Options?

• (A) Effective antiviral medication: No effective antiviral for smallpox existed at the time of its eradication. This was not a factor.

• (B) Absence of an animal reservoir: This was a necessary prerequisite for eradication (the virus only infected humans), but it was not the active tool used to achieve it. The vaccine was the tool.

• (D) Inability to form latent infections: While true (it was an acute infection only), this was another biological characteristic that made eradication possible, but it was not the active intervention.

• (E) Susceptibility to disinfectants: This might aid in infection control in a hospital setting but was irrelevant to the large-scale public health strategy that spanned the globe.

Histopathological Correlation:

• Biopsy of a lesion would show ballooning degeneration and reticular degeneration of keratinocytes, leading to multiloculated vesicles.

• Guarnieri bodies (large, eosinophilic cytoplasmic inclusions containing viral particles) were a pathognomonic finding in infected cells.

The eradication of smallpox remains one of the greatest achievements in medicine and public health, made possible by the strategic use of a highly effective vaccine.