Etiology and morphological features
The disease is caused by variola virus, a large DNA-containing agent. Clinical morphology distinguishes two key specific features:
- Paschen bodies — clusters of viral particles visualized under a light microscope with special staining.
- Guarnieri bodies — small granular clusters of the virus inside epithelial cells, which are an absolutely specific sign of smallpox.
In severe forms of intoxication, hemorrhagic inflammation may develop (also characteristic of influenza, plague, and anthrax). Due to a sharp increase in microvascular permeability, erythrocyte diapedesis occurs. When blood contacts air, hemoglobin undergoes changes, causing the exudate to turn black—a phenomenon known as the "black smallpox" phenomenon.
Epidemiology and transmission routes
By its nature, the infection is an anthroponosis: humans are the sole reservoir and source of infection.
Main routes of transmission:
- Aerogenic route — airborne mechanism is the primary one.
- Contact route — transmission of the virus via the patient's clothing or personal items.
Historically, smallpox pandemics claimed millions of lives in India, Pakistan, Egypt, and the Arabian Peninsula. In Europe alone, the disease claimed the lives of at least 12–15 million people, with overall mortality reaching 40%.
Prevention and immunity
Mass specific prevention played a key role in overcoming the infection:
- Discovery: the smallpox vaccine was developed by Edward Jenner in 1796.
- Duration of protection: routine vaccination provides immunity for a period of 3–5 years.
- Revaccination: was previously performed every 7–8 years; infection during the inter-vaccination period resulted in a milder course of the disease.
- Emergency measures: administration of the vaccine during the incubation period effectively prevents the development of clinical manifestations of the disease.
Jenner — 1796 — DNA virus — Guarnieri (specific marker in cells).
Class and exam questions
Which virus causes smallpox?
The disease is caused by variola virus, a large DNA-containing virus.
Which morphological structures are specific to smallpox?
Specific diagnostic features include Guarnieri bodies (viral clusters in epithelial cells), as well as Paschen bodies, visible with special staining.
Why does the epidemiological threat of smallpox persist if it has been eradicated?
The threat persists due to the discontinuation of widespread vaccination, leaving the modern global population completely defenseless against this quarantine infection.
What are the main mechanisms of transmission of the infection?
Transmission occurs from person to person (anthroponosis) via airborne droplets or through direct contact with the patient's belongings and clothing.
What else to study on this topic
- Features of hemorrhagic inflammation in particularly dangerous infections
- History of creation and mechanism of action of E. Jenner's first vaccine
- Differential diagnosis of smallpox with other exanthems
- The role of quarantine infections in the structure of epidemiological threats
- Complications and outcomes of severe forms of viral infections
Master the complete topic in the «Infectious Diseases» course
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