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IB Biology Option F AHL

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  1. 1. Epidemiology<br />AHL IB Biology<br />
  2. 2. What is epidemiology?<br />The study of the spread of disease and the factors that influence its spread<br />
  3. 3. Emerging Infectious Disease<br />Mutation of organism to new serovar (antigenic type)<br />Migration of humans and animals into new environments<br />Travel<br />War and natural disasters<br />Decline in vaccination rates<br />Climatic changes<br />
  4. 4. Microbe of the Day<br />Vibriocholerae<br />Gram negative curved rod<br />Toxin alters sodium pump in intestinal cells  fluid loss<br />Water-borne bacteria<br />High virulence and can kill within hours<br />
  5. 5. London in the 1800s – what comes to mind when you see these pictures?<br />
  6. 6. 31st August 1854<br />Outbreak of cholera in the Soho section of London<br />In a single night 56 cases of cholera were reported all within a few block of each other<br />Nearly 500 people lost their lives before the outbreak was over<br />
  7. 7. What is wrong with these posters?<br />
  8. 8. The Miasma Theory<br />People lived in very crowded conditions<br />The streets full of sewage and livestock<br />900 people in 2 buildings <br />-180feet deep x 5 stories <br />– 1 pump a block away, privy in yard<br />Germ theory of disease not widely accepted<br />People believed that bad smells carried disease<br />But one man thought otherwise…..<br />
  9. 9. The father of epidemiology – John Snow<br />He noticed people with cholera developed immediate digestive problems<br /> -cramps<br />-vomiting<br />-diarrhea<br />Face, feet, hands shriveled and turned blue<br />-died in less than a day<br />Probably spread by vomiting and diarrhea<br />He thought the disease was being spread through a contaminated water source but no one believed him<br />
  10. 10. John Snow uses the Scientific method to prove the skeptics wrong<br />Comparison of pump location with cholera deaths<br />-first 3 days of epidemic<br />
  11. 11. The Great Experiment<br />Two water companies supplied central London<br />Customers mixed in same neighborhood<br />Snow went door to door asking which water company served home and compared locations with cholera data<br />
  12. 12. He went door to door questioning everyone who drank from the pump and recording their symptoms…<br />Of 83 people infected<br />-only 10 lived closer to a different pump than Broad Street<br />Of these 10<br />5 preferred taste of Broad Street water <br />3 were children who went to nearby school<br />
  13. 13.
  14. 14. The Great Experiment<br />Lambeth Company: <br />-water intake upstream of London<br />-sewage outfall into Thames<br />Southwark & Vauxhall Company: -water intake downstream of sewage outfall<br />
  15. 15. The Great Experiment<br />
  16. 16. Controlling the spread of infection<br />Snow convinced neighborhood council to let him remove handle from water pump on Broad Street <br />- number of new cases declined dramatically<br />Many on council still not convinced by his evidence<br />
  17. 17. Later, people learned that the well below the pump was about 28 feet deep. <br />But close by ran a sewer that was only 22 feet below ground level. <br />A few days before people got sick, some people remembered a bad smell near the pump. <br />The raw sewage had seeped through the ground and into the well. <br />As more people got sick, the sewage contained more of the microbes that caused cholera. <br />That made the water even more contaminated<br />
  18. 18.
  19. 19. Now try the Cholera Outbreak worksheet<br />
  20. 20. Epidemics can lead to pandemics<br />A large number of people in different countries all suffering from the same infection<br />AIDS<br />1981<br />25 MILLION DEATHS<br />BUBONIC PLAGUE<br />1348<br />25 MILLION DEATHS<br />H5N1 BIRD FlU<br />2003<br />307 DEATHS<br />SPANISH FLU<br />1918<br />50-100 MILLION DEATHS<br />
  21. 21. The Black Death<br />Yersiniapestis is the bacterium that causes the Black Death plague. <br />Infected fleas transmit yersiniapestis primarily among rodents. <br />When a plague outbreak among rodents kills many of them, infected fleas that were feeding on the rodents' blood jump to other animals and humans, carrying the infection with them. <br />Electron micrograph image<br />
  22. 22.
  23. 23. Bubonic plague<br />This is the most common type of plague in humans, accounting for the majority of naturally occurring cases. <br />Bubonic plague is characterized by an enlarged, infected lymph node called a bubo.<br />
  24. 24. Septicemic Plague<br />Septicemic plague occurs when plague bacteria multiply in your bloodstream. <br />You can contract this form of plague when bacteria transmitted by a fleabite enter directly into your bloodstream, or as a complication of bubonic or pneumonic plague. <br />
  25. 25. Pneumonic Plague<br /><ul><li>You can also develop pneumonic plague as a complication of bubonic or septicemic plague, if the bacteria spread to your lungs.
  26. 26. Pneumonic plague progresses rapidly and may cause respiratory failure and shock within two days of infection. </li></li></ul><li>
  27. 27. Europe Before the Black Death<br /><ul><li>By the early 1300’s Europe was experiencing a mini ice age.
  28. 28. Unusually heavy rains between 1315 and 1319 destroyed grain crops across Europe.
  29. 29. Many Europeans died or were weakened by famine (widespread starvation).</li></ul>How will this affect the ability of the population to resist infection?<br />
  30. 30. Origins<br /><ul><li>Bubonic plague was first seen in China c. 1331
  31. 31. In 15 years had spread across Asia to the Black Sea. </li></li></ul><li>The Black Death in Europe<br />
  32. 32. Medieval Art indicate the effects of the Plague<br />Bring out your dead!<br />An obsession with death.<br />Boccaccio inThe Decameron<br />“The victims ate lunch with their friends and dinner with their ancestors”<br />The Danse Macabre<br />
  33. 33. Attempts to Stop the Plague<br />Flagellanti:Self-inflicted “penance” for our sins!<br />“Leeching”<br />MEDIEVAL CURES<br />1. The swellings should be softened with figs and cooked onions. The onions should be mixed with yeast and butter. Then open the swellings with a knife.<br />2. Take a live frog and put its belly on the plague sore. The frog will swell up and burst. Keep doing this with further frogs until they stop bursting. Some people say that a dried toad will do the job better.<br />A Doctor’s Robe<br />
  34. 34. Pogramsagainst the Jews<br />“Golden Circle” obligatory badge<br />“Jew” hat<br />Burning Jews<br />
  35. 35. The Consequences of The Black Death<br />Have a look at a primary source from the time of the Black Death and try and answer the questions<br />