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Health Studies
Caroline Barakat

HLTA01H3F- The Power of Plagues Lecture 2 Definitions Parasites: organism that grows, feeds, and is sheltered on or in a different organism and that does not contribute to the survival of its host Virus: ultimate micro-parasite- smaller than bacteria; neither cells nor organisms; can only reproduce within their host Macro-parasites: composed of many cells; cycles through transmission stages (eggs and larvae) which pass into the external environment Transmission: movement of a parasite from one host to another Incubation period: interval of time required for development of a disease Latent period: seemingly inactive period between exposure to an infection and subsequent illness Parasite virulence: capacity of a parasite to cause disease Zoonotic infections: animal infections that can be transmitted to humans What are the main factors that influence the occurrence of a disease? 1. Host  Immunity  Genetics  Nutrition 2. Environment  Promotes exposure 3. Agent  Biological, physical, chemical, psychosocial, rate of growth, persistence Modes of Disease Transmission  Direct transmission: from person to person  Indirect: through a common route/vector, e.g. contaminated air/water, mosquito  Dermal: through the skin, e.g. fungus  Ingestion: through the mouth, e.g. E. coli in water  Inhalation: during respiration e.g. particulate matter  Aspiration: airway entry Types of Diseases  Broad spectrum if disease severity- Iceberg concept  Clinical Disease o Classical and severe disease o Moderate severity; mild illness  Subclinical Disease o Infection without clinical illness (asymptomatic infection) o Exposure without infection Types of Disease Outbreaks Three main types:  Endemic: usual occurrence of a disease within a given geographical a  rea  Epidemic occurrence of a disease Determinants of disease outbreaks:  Herd immunity: resistance of a group to a disease attack due to immunity o For measles- estimate that 94% of the population must be immune  Incubation period  Attack rate: ratio of the number of people in whom a certain illness develops/total number of people at risk Definition of Plagues In the past, all disease outbreaks- plagues. ‘plaga’ i.e. ‘to strike a blow that wounds’ Epidemic (Geek origin)  ‘epi’ “among” and ‘demos’ Historical Perspective  Belief that our ancestors ‘hunter-gatherers’ were healthyAgricultural Revolution  Domesticated animals  Lived in one area and were exposed to many more parasites  People lived in close proximity to each other  Spread of diseases easily  Irrigation became popular  Zoonotic diseases started to affect humans Technological advancements  Can speed disease control  Can also speed transimission  Efficiency in transportation makes it easy to spread diseases from one part of the world to another in a short amount of time e.g. confined areas of an aircraft Legionnaires Disease- 1976  The suspected source of the disease is through wet cooling/air conditioning systems Toxic Shock Symptoms (traced to 1979)  Caused from a bacteria found in high absorbancy tampons  When these tampons were moved from the market, the outbreak of TSS drastically declined SARS- traced to Feb 2003  Was spread from China to Canada when a person travelled Lecture 3 The Antonine Plague  soldiers coming from Mesopotamia back to Rome brought the disease to the Roman Empire  According to the symptoms, it could have been the first record of smallpox  Caused more than 2000 deaths in Rome per dayThe Cyprian Plague  Originated in Ethiopia, moved to Egypt, then to the Roman colonies of North Africa  Could be the first record of measles or smallpox  Pandemic lasted for about 16 years  These 3 plagues could have been the fall of the Roman Empire Justinian Plague  First pandemic of the Bubonic Plague  Started in 541 in Constantine  Raged Europe, North Africa and the Middle East until 7  1 million people in 5 years  By 600 AD mortality at 100 million in western Europe Bubonic Plague present in three parts  Justinian Plague  ‘Black Death’- 1346 to 1352  1860s in the Yunnan region of China  A smaller outbreak of the Bubonic plague, but significant because it reached other parts of the world  The Bubonic plague mostly impacted major cities that were close to the water and where trade happened  The plague was started by a certain type of rat  These rats were able to reach these cities through the trains and boats that were used for trading Impacts  Quarantine: people were told to stay away from others in order to prevent the spread of disease; people were left on a ship on see for 40 days ; although the people were not on land, the rats were still able to find a way to land and spread the disease  Pest houses  Quick burials: buried those who died of the disease quickly to avoid it from spreading more; burning of corpses was also common  Burning of clothes and bedding  Studies of human anatomy  Theory of Contagion- Girolamo Fracastoro (1478-1553)  Changes to farming: raising of sheep for wool became popular because it required less labour; led to inflation  Bigger ships- smaller crews  New diversified economy  Local universities: instead of sending students to universities far away, there were now local universities which would help to control the spread of the plague Cause th  The cause of the Bubonic plague was not discovered until the 19 century  Plague microbe was discovered by Alexander Yersin; named Yersinia pestis  1898- plague linked to fleas on rats Types of Plague  Most cases are bubonic plague  Infection- from the bites of a flea that previously fed on an infected rodent  Bacteria spreads to lymph nodes which swell (called bubo)  Septicemic plague: without the development of buboes; infection of the blood  Pneumonic plague: bacteria moves through the bloodstream to the lungs; rapid fatal form of the disease; death can occur in hours; can transmit from human to human  Y. pestis is a highly pathogenic bacteria Pneumonic Plague Symptoms  Severe cough  Frothy, bloody sputum  Difficulty breathing  Death occurs within 24 hours “Black Death”  75 million people dead  One-third to two-thirds of Europe’s population  In Europe, port cities were most affected, then trade routes, both sea and land  30 to 75%- mortality rate from bubonic plague  Pneumonic plague- (2 most common): mortality rate of 90-95%Lecture 3 History  Egyptian Papyrus documents (1550 BC)  Indian writing, approximately 600 BC  In records of ancient Greesde, afte r the army of Alexander the Great returned from India (320 BC)  In Rome, (BC) with the return of Pompeii  Disease of the soul o Lepers were often outcast o Was thought to be contagious  Earlier thought to be a hereditary illness, or caused by a curse or by punishment from God  Lepers were stigmatize o E.g. special clothing, arrival notification, separate hospitals, and often had to live in colonies call leprosariums/lazaretto/leper colony/lazar house  first “leper house” in England 936 AD th  mid 12 century- loss of civic status, removal from public office  13 century- 19,000 ‘leprosaria’ in use  Mass of Separation  Decline around 1350  Spread to North America o First case in Hawaii o In 1997 the last people in a leprosarium in America were set free Dr. Armauer Hansen of Norway- 1873  Discovered the leprosy germ under a microscope  Very sl Etiology  M. leprae  Slow multiplying, bacillus o Average doubling time of 12-14 days  Thought to be transmitted via droplets, from the nose during close and frequent contact  Not highly infectious- may be related to genetic susceptibility  Mainly affects the skin, nerves, and mucous membranes o Link between tuberculosis and leprosy o People who get a vaccine for T.B. are less likely to get leprosy, not vice versa. Epidemiology  A lot of cases in Brazil, India, and some African countries  In the 1960s and 1970s, there was a high number of cases of leprosy in China Risk  Leprosy can affect peop
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