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Variola Virus. Photo Courtesy of CDC/Public Health Image Library 1. History. Ancient scourge – many millions killed Global eradication in 1977. Photo Courtesy of National Archives. Photo Courtesy of World Health Organization 2. Bioweapon Potential. Precedence
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Variola Virus Photo Courtesy of CDC/Public Health Image Library1
History • Ancient scourge – many millions killed • Global eradication in 1977
Bioweapon Potential • Precedence • Prior use in French-Indian War • Produced by USSR
Bioweapon Potential • Reality of the risk • Viral stocks exist • Non-immune population
Epidemiology • No animal reservoir/vector • Mortality 25-30% • Person-to-person transmission • Via respiratory droplets • Household and face-to-face contacts • High risk of nosocomial spread • Secondary attack rate 25-40% • Up to 20 contacts infected per case
Epidemiology • Aerosol route of transmission • Likely in bioterrorism setting
Virology • Orthopoxviridae DNA Viruses • Variola variants • Variola major – high mortality • Variola minor – low mortality, 20th Century • Vaccinia • Current smallpox vaccine
Virology • Orthopoxviridae DNA Viruses • Other pox viruses • Cowpox • Monkeypox
Pathogenesis Virus contacts respiratory mucosa Carried to lymph nodes Primary viremia Organ seeding WBCs infected Dermal invasion Vesicle Sepsis
Clinical Features • Incubation Stage • Asymptomatic • 10-12 days (range 7-17)
Clinical Features • Prodromal Stage • Sudden nonspecific flu-like illness • High fevers • Headache • Backache • Prostration • 2-5 days duration
Clinical Features • Eruptive Stage • Characteristic rash • Centrifugal location • Grouping • Depth of lesions
Clinical Features • Distribution of the rash
Clinical Features • Severity of the classical rash • Discrete (<10% mortality) • Semi-confluent (25-50%) • Confluent (50-75%)
Discrete Smallpox Photo Courtesy of National Archives
Semi-Confluent Smallpox Photo Courtesy of World Health Organization20
Confluent Smallpox Photo Courtesy of National Archives
Smallpox Complications • Eye infection or blindness • Arthritis • Encephalitis • Secondary bacterial infections
Differential Diagnosis • Varicella (chickenpox) • Monkeypox • Drug eruptions • Generalized vaccinia • Multiple insect bites • Molluscum contagiosum • Secondary syphilis • Viral exanthems (e.g. HHV-6, Cocksackie, etc)
Chickenpox Photo Courtesy of World Health Organization21
Monkey Pox Photo Courtesy of CDC22
Erythema Multiforme Photo Courtesy of New England Journal of Medicine23
Generalized Vaccinia Photo Courtesy of CDC24
Generalized Vaccinia Photo Courtesy of CDC25
Molluscum Contagiosum Photo Courtesy of American Academy of Pediatrics26
Secondary Syphilis Photo Courtesy of American Academy of Pediatrics27
Hand-Foot-Mouth Disease(Enterovirus Infection) Photo Courtesy of American Academy of Pediatrics28
Differential Diagnosis • Chickenpox (varicella virus) • Distribution of rash • Grouping of lesions • Asynchronous development • Vesicle appearance • Shallow • Short Prodrome
Chickenpox Photo Courtesy of World Health Organization29