FLOWCHART ON POXVIRIDAE!
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Properties of poxviridae
• Largest family of viruses
• Unique oval-shape
• Antigenically very complex
• Remains stable in air for hours
Genome
• Linear double stranded DNA covalently cross-linked at ends
• Terminal repeated sequences
• Inverted repeats at both ends
Clinical Features
• Human only
• Respiratory Secretions
• Always associated with skin lesions
• At least 9 poxviruses cause disease in human
• Variola and Vaccinia
• 7–12 days of incubation
• Initially influenza-like symptoms
• Characteristic pustules
• Scarring of skins
• Neurological damage
• Blindness
• Death
Variola
Variola Major
• 25–30% fatalities
Variola Minor
• Less than 1% death
Practice of variolation
• Smallpox from receipients to protect against future infection
Edward Jenner
• Vaccination
- Used cowpox from milkmaids
- Vaccinate an 8-year-old James Phipps
- Then the cowpox strain challenged with smallpox.
Vaccinia
• Evolved from cowpox or smallpox
• Used as a vector
Eradication of smallpox
• no reservior for VV except fro man
• VV causes only acute infection from which the patient dies
• or, obtains lifelong immunity
• VV is an effective immunogen
• certified by WHO in 1980 to be defeated