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EPIDEMIOLOGY

EPIDEMIOLOGY. Daniel Cothran BIOL 422 – Microbiology 10/19/2009. Overview. Introduction to Public Health What is Epidemiology? History Who Uses It? Terminology Infectious Disease Transmission The Host Community Disease Burden. Introduction to Public Health.

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EPIDEMIOLOGY

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  1. EPIDEMIOLOGY Daniel Cothran BIOL 422 – Microbiology 10/19/2009

  2. Overview • Introduction to Public Health • What is Epidemiology? • History • Who Uses It? • Terminology • Infectious Disease Transmission • The Host Community • Disease Burden

  3. Introduction to Public Health

  4. Introduction to Pubic Health What is it? • A field devoted to the promotion and maintenance of well-being Attributes • Multidisciplinary • Often focused on prevention rather than treatment (upstream) • Operates on multiple levels

  5. Introduction to Public Health (cont’d)

  6. What is Epidemiology?

  7. What is Epidemiology? Two Definitions: • “The study of the occurrence, distribution, and determinants of health and disease in a population” • “The study of the distribution and determinants of disease frequency in human populations and the application of this study to control health problems”

  8. History of Epidemiology • Almost 400 years old! • “First” epidemiologist: John Graunt • William Farr • Controlled trials! (public health people love these) • Shift from studying infectious to chronic diseases • Divergence: molecular and genetic epidemiology vs. social epidemiology

  9. Who Uses Epidemiology? • Health Care Service Providers • Governments • Legislature • Health Departments • International Health & Development Agencies • Community-based NGOs • Researchers • Journalists • You

  10. Terminology

  11. Terminology

  12. Terminology (cont’d) • Case • An instance of a disease or health condition in an individual • Incidence • Number of new cases of a disease or health condition in a population over a given period of time • Prevalence • Number of new and existing cases of a disease or health condition in a population over a given time period

  13. Hand Check!

  14. What’s are the incidence and prevalence for the class? • Incidence = _____ / ~70 (per hour) • Prevalence = ___ +___ /~70 (per hour Symptoms of Glitter Disease

  15. Terminology (cont’d) • Morbidity • Used commonly to mean illness • Morbidity Rate: refers to the incidence of disease in a population • Mortality • Used commonly to mean death • Mortality Rate: refers to the incidence of death in a population • Morbidity from a disease can be high without mortality being high

  16. Terminology (cont’d) • Host – organism capable of supporting the growth of a virus or other parasite • Carrier – sub-clinically infected individuals who may spread a disease • Examples?

  17. Terminology (cont’d) • Reservoir – source of viable infectious agents from which individuals may be infected • Vector – agent (usually insect or animal) able to carry pathogens from one host to another • Vehicle – nonliving source of pathogens that infect large numbers of individuals (food, water, etc)

  18. Terminology (cont’d) • Zoonosis – a disease, primarily of animals, that is occasionally transmitted to humans • Examples: avian and swine flu Don’t forget to cover your snout when you sneeze!

  19. Terminology (cont’d) Disease Progression • Infection • Incubation Period • Acute Period • Decline Period • Convalescent Period

  20. Disease Transmission

  21. Direct Host-to-Host Transmission • Pathogen transmitted directly from host to host • Respiratory illnesses • Sexually-transmitted infections • Skin infections • Vampirism? 

  22. Indirect Host-to-Host Transmission • Transmitted through living agents (vectors) or inanimate agents (vehicles) Mosquito: vector Lenoir food: vehicle

  23. What type of transmission was at work here?

  24. Epidemics Common-source epidemic • Transmission can occur rapidly • Classic example: London’s cholera epidemic in the 1850’s

  25. Epidemics (cont’d) Host-to-Host Epidemic • Typically occurs over a longer period of time than the common-source epidemic • Examples: Influenza, Chickenpox

  26. Epidemics (cont’d)

  27. The Host Community

  28. Coevolution • The continued existence of host and pathogen frequently requires coevolution • Examples • Myxoma • Malaria • E. coli

  29. Herd Immunity Is this what it is?

  30. Herd Immunity (cont’d) • Resistance of a group to infection due to the immunity of a high proportion of individuals • Depends on: • Density of the population • Virulence of the agent

  31. The Host Community • Disease is not purely biological! • Behavior matters • Examples of protective behaviors? • Who you are matters • Racism • sexism • classism • Etc.

  32. Disease Burden

  33. Disease Burden

  34. Disease Burden (cont’d)

  35. Sources • Aschengrau A, Seage G. Essentials of Epidemiology in Public Health. 2nd Ed. Jones and Bartlett Publishers, Inc. Salsbury, MA, 2008. • Clark DP, Dunlap PV, Madigan MT, Marinko MM. Brock Biology of Microorganisms. 12th Ed. Pearson Edu, Inc. San Fransisco, CA, 2009. • http://a3.vox.com/6a00c2252582c1f21900d4144dabbb6a47-500pi • http://himetop.wdfiles.com/local--files/broad-street-pump/Broad%20Street%20Pump.jpg • http://mydogumentary.files.wordpress.com/2009/08/mosquito.jpg • http://farm4.static.flickr.com/3123/2604408184_5718abdaa8.jpg • http://www.independent.co.uk/multimedia/archive/00079/twilight_79981t.jpg • http://images.buyfairycostumes.com/deluxe-fairy-makeup.jpg • http://www.measlesinitiative.org/mi/photos • http://www.whspip.co.uk/images/occu2.jpg • http://www.msf.ca/blogs/cholera/files/2009/03/latrine.jpg • http://www.youtube.com/watch?v=6Pq98sZSBtc • http://www.medicine.manchester.ac.uk/images/epidemiology/home_checkerboard.jpg • http://www.youtube.com/watch?v=LU8DDYz68kM • http://www.dailytarheel.com/content/fewer-h1n1-cases-reported

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