5. EPIDEMIOLOGY

6. Koch’s Postulates (1876)

7. Koch’s Postulates To prove that a given microorganism is the pathogen for a certain disease one must 1.Isolate From Afflicted Individual 2.Culture 3.Reinfect Previously Unafflicted Individual 4.The previously unafflicted individual must develop the same symptoms/disease state as the original host

9. Host Def: Individual afflicted with disease Factors Affecting Host – Genetic Predisposition – Active Immunity – Other diseases

10. Example: Individuals with Thalassemia Are Not Good Hosts For Malaria

11. Reservoir Def: Naturally occurring population that carries the pathogen. Continual source of pathogen. Example: Cows and Anthrax

12. Antigenic Shift Def: Mutation in the pathogen population that changes their antigens (i.e. proteins that identify them to our immune systems) Antigenic shifts allow diseases to jump from one species to another

16. Pathogen Def: What causes the disease in the host

17. One pathogen: One disease The causative agent of Anthrax is Bacillus anthracis. The causative agent of Lyme Disease is Borellia burgdorferi You cannot get Lyme Disease from Bacillus anthracis

18. Vector Def: The agent that transfers the pathogen from host to host

20. Mosquitoes Most dangerous animal in world (for humans) Vectors for malaria, dengue, encephalitis, yellow fever, heartworm

21. EPI Curves

23. What causes some diseases to become pandemic while others are epidemic or endemic?

24. R 0 = Basic Reproductive Number Measurement of how many cases will generally derive from a single case of a given disease R 0 < 1 = disease will not spread R 0 > 1 = disease will spread

25. Comparative R 0 Values DiseaseVectorR0R0 MeaslesAirborne12-18 PertussisAirborne Droplet12-17 SmallpoxTouching5-7 PolioFecal-Oral5-7 HIVSexual Contact2-5 Influenza (1918)Airborne Droplet2-3

26. Virulence Def: How much does the pathogen affect the host Example: Ebola is so virulent, killing the host so rapidly, that it is difficult for the disease to spread to other hosts

27. Endemic A disease that is commonly present in a population, generally at low frequencies Ex: Malaria, Streptococcus A

28. Epidemic Large number of afflicted hosts in a small area in a short period of time Epidemics are generally short-lived due to rapid virulence/effects and limited number of hosts EX: Ebola

29. PANDEMIC Disease that spreads worldwide, creating thousands of cases Generally, pandemic diseases require common vectors and long incubations or lysogenic modes Ex: Tuberculosis

30. Sudden Acute Respiratory Syndrome

32. How Does The Balance of The Viral Life Cycles Determine If A Disease Is An Epidemic, Endemic or Pandemic?

34. LAB: Interactive Epidemiology Purpose: To examine the effects of several parameters of communicable diseases on their epidemiological profile Method: mathematical modeling

35. Part 1: NIH Disease Transmission Simulator

37. Part Two: Pop. Density & Mobility