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Transcript
Smallpox Smallpox (caused by the variola virus) has its origins in cowpox and/or monkey pox It likely became a human disease ~4,000 years ago The disease exists in two main clinical forms: Variola minor, which is relatively mild and had a modern case fatality rate of ~1% Variola major, which can be quite severe, and had a modern case fatality rate of ~30% The incubation period lasts 7-17 days, during which the infective is not contagious The initial period of the disease echos many other illnesses, and the infective may be contagious Pustules and, eventually, scabs form; death may result from high fever The disease is primarily spread by person-to-person respiratory drop transmission; it can also (more rarely) be spread by objects Smallpox in History There is evidence of smallpox-like pustules on the mummy of Ramses V Historical accounts of smallpox include: Athens 430BCE Rome 165CE China, Japan, and Korea 300–600CE By 1100–1300CE, smallpox outbreaks had been recorded throughout the Old World Smallpox epidemics were recorded in the New World in the 1600s Smallpox reached the South Pacific in the 1800s Prior to the 19th Century, smallpox caused ~33% of child mortality; ~400,000 deaths per year The Columbian Exchange During the 16th–19th Centuries, the Old World disease pool expanded globally through Overseas exploration, trade, conquest, and colonization The arrival of Europeans in the New World introduced exotic species New animals included horses, cows, sheep, pigs, chickens, and rat New plants included barley, wheat, oats, and a variety of weed plants Novel bacteria and viruses were introduced to a “naïve” population: smallpox, influenza, measles, typhus, malaria, diphtheria, whopping cough, plague, and cholera Many imported species, without natural predators, out-competed and eventually displaced indigenous species New insects included the honeybee, and the mosquitos that transmit malaria Europe got maize, potatoes, coffee, cocoa, chilies, pineapples, squash, pumpkins, peanuts, cassava, beans, tomatoes, vanilla, avocados, quinine, turkeys…and tobacco, coca leaf, and syphilis Virgin Soil Epidemics “Virgin soil” epidemics occur in populations with no prior experience of a particular infectious disease The population consists of 100% susceptibles e.g. The Yanomami of the Amazon rainforest, Brazil A 1968 measles epidemic yielded a death rate of 10%, despite modern medical care by missionaries and nurses Between 1968 and 2001, the population of one village dropped from ~3,000 to 200 individuals Disease Epidemics Why were there such high death rates of Indigenous peoples due to European diseases? No epidemic disease experience (perhaps resulting in an extreme immune response) Everyone gets sick at the same time There is an inability to nurse the sick, fetch water and firewood, and to harvest crops No quarantine Immediate Impacts: 50-90% depopulation over a few years Famine The loss of elders and leaders Psychological numbing, despair, and suicide Long-term impacts: Loss of traditional beliefs and conversion to Christianity Increased reliance on European technology Social and political disruption; civil wars Abandonment of homelands and the creation of refugees Smallpox in the New World Indigenous populations suffered a 40-60% mortality rate when exposed to smallpox Major epidemics were recorded in: 1521 (Aztec) 1525 (Inca) 1633 (Northeast) 1838 (Plains) 1862 (Coastal B.C.) Smallpox and the African Slave Trade Smallpox contributed significantly to the depopulation of the New World, creating a ‘need’ for new slave labour From the 16th to 19th Centuries, approximately 11,000,000 Africans were enslaved 10-40% of those captured died on slave ships Variolation Involves inoculation with the smallpox virus The procedure used dried material taken from scabs; this material was blown or inhaled into the nose The weakened virus caused a milder form of the infection Variolation had a mortality rate of ~2%, as opposed to 30% due to natural exposure Practiced in China ~1100C.E.; introduced to the Americas by African slaves Lady Mary Wortley Montagu (British royalty) suggested it be tried on prisoners and orphans in 1721 The experiment was successful and was used on the royal family As a result, the procedure was fashionable from the 1740s – 1780s Vaccination Vaccination involved inoculation with the cowpox virus (now vaccinia virus), pioneered by Edward Jenner Widespread in Britain by 1796 In the 1800s, it was employed in Europe and the New World Vaccination had a very low mortality rate: ~1/100,000 to 1/1,000,000 Vaccination and Public Health Britain – compulsory vaccination 1799 – soldiers 1840 – free for the poor 1853 – all infants 1871, 1874 – all children Continental Europe 1816 in Scandinavia and Russia 1902 in France Compulsory vaccination raised ethical questions: Individual vs. Collective rights Prevention vs. Destruction 20th Century outbreaks in New York highlight the risk of low vaccination uptake These concerns apply to vaccines more generally, as recent outbreaks of measles and whooping cough suggest Resistance to Vaccination The reasons for anti-vaccination movements around smallpox: Vaccinations were painful and caused smallpox Compulsory vaccinations represent interference by the state Vaccinations are against God’s will The middle class saw smallpox as a disease of the poor; the vaccination scar was a sort of “branding” Eradication of Smallpox North America/Europe: 1949 Smallpox Eradication Program commenced in 1966 Most of Africa by 1970 Asia by 1975 The last natural case of smallpox occurred in Somali in 1977 WHO declared smallpox as eradicated on Dec. 9, 1979 Storage of Smallpox Samples of smallpox are kept in secure labs at the CDC in Atlanta, and at the Vector Institute, in Koltsovo, Russia Why store live smallpox? Because of the risk of bioterrorism Because of the potential for an accidental outbreak or mutation of the monkeypox virus For research into safer vaccines