1. Introduction to 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. 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

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: vectorLenoir 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

34. Disease Burden (cont’d)

35. Sources Aschengrau A, Seage G. Essentials of Epidemiology in Public Health. 2 nd Ed. Jones and Bartlett Publishers, Inc. Salsbury, MA, 2008. Clark DP, Dunlap PV, Madigan MT, Marinko MM. Brock Biology of Microorganisms. 12 th 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