HLTB21H3 Lecture Notes - Lecture 7: Middle Ages, Mortality Rate, Smallpox Vaccine

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2 Dec 2012
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Lecture 7 Smallpox (Variola)
Smallpox is an “old world” disease which has no classification limits (rich/poor equally affected)
10 000 BC, the first agriculture settlements in North Eastern Africa the smallpox virus was
spread from here by ancient Egyptian merchants
Earliest evidence on Egyptian mummies
Pharaoh Ramses V
Smallpox is described in historical China, and is mentioned in the ancient texts of India
In Europe there was a frequent smallpox epidemic during the middle ages, and 16th century
London
Effects of Smallpox
Plague of Antonine was responsible for the fall of the Roman Empire
Not completely sure it was smallpox
New world in the 16th century, victory of the explorers over the native population
Fall of the great empires of the Aztecs and Incas
Used to help settle North America
Captain Ecuyer (first use of biological warfare; 18th century) used blankets and
handkerchiefs infected with smallpox, to spread the disease to the native
population
Etiology
Virus: Orthopoxvirus poxviridae
Common name: Variola virus
Major 30% virulence
Minor 2% virulence
Monkey pox is the same as small pox with a lower virulence
Haemorrhagic smallpox or black pox develops in 5-10% of cases
Malignant and haemorrhagic form of variola major
Mortality rate of 95%
Transmission
Continuously transmitted, with no long term carries
Enters body by inhalation (person to person contact)
Smallpox does not exist in animals, however there are related pox viruses present in animals
Smallpox is spread by direct contact though inhalation
Animal reservoirs do not exist
Virus multiplies in mucus membranes and then moves to the lymph nodes --> where it
advances to the internal organs --> eventually reaching the bloodstream
Virus can only survive for approximately 2 days outside of a human host
Incubation period of 9 14 days
Clinical Manifestation
Acute onset; fever, malaise, rigors, vomiting, headache, backache and occasionally delirium
Within 2 3 days the skin lesions appear
8 14 days later pustules develop scabs and heal
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