Module 7: Outbreak Investigation & Disease Control

1. Module 7:Outbreak Investigation & Disease Control Outbreak Investigation Developed through the APTR Initiative to Enhance Prevention and Population Health Education in collaboration with the Brody School of Medicine at East Carolina University with funding from the Centers for Disease Control and Prevention

2. Acknowledgments APTR wishes to acknowledge the following individuals that developed this module: • Kristina Simeonsson, MD, MSPH Department of Public Health Brody School of Medicine at East Carolina University • Julie Daugherty, MPH Department of Public Health Brody School of Medicine at East Carolina University This education module is made possible through the Centers for Disease Control and Prevention (CDC) and the Association for Prevention Teaching and Research (APTR) Cooperative Agreement, No. 5U50CD300860. The module represents the opinions of the author(s) and does not necessarily represent the views of the Centers for Disease Control and Prevention or the Association for Prevention Teaching and Research.

4. Foodborne Outbreaks in the News

5. Presentation Objectives • Define the terms outbreak, epidemic and pandemic • Discuss reasons that outbreaks occur • Understand the rationale for investigating outbreaks • Describe the steps of an outbreak investigation

6. Is Their a Difference between an Epidemic and an Outbreak? • EPIDEMIC • Occurrence of more cases of disease than expected in a given area or among a specific group of people over a particular period of time • OUTBREAK • Epidemic limited to localized increase in the incidence of disease • CLUSTER • Aggregation of cases in a given area over a particular period without regard to whether the number of cases is more than expected

7. What is a Pandemic? • An epidemic occurring over a widespread area and usually affecting a substantial proportion of the population • Influenza • Severe acute respiratory syndrome (SARS) • Tuberculosis • Acquired immunodeficiency syndrome (AIDS)

8. http://www.cdc.gov/ncidod/osr/site/about/graph.htm

9. Increase in amount or virulence • Introduction into setting where it has not been before • Enhanced mode of transmission TRANSMISSION • Change in susceptibility • Factors that increase exposure • Conducive to interaction between host and agent

10. Why Investigate Outbreaks? • Prevention and control • Research • Public concern • Political interest • Program considerations • Training http://www2a.cdc.gov/TCEOnline/

11. Steps of an Outbreak Investigation • Establish existence of an outbreak • Verify the diagnosis • Define a case • Identify additional cases • Perform descriptive epidemiology • Develop and test hypothesis • Reconsider hypothesis • Perform additional studies if needed • Implement control measures • Communicate findings

12. Steps of an Outbreak Investigation • Establish existence of an outbreak • Verify the diagnosis • Define a case • Identify additional cases • Perform descriptive epidemiology • Develop and test hypothesis • Reconsider hypothesis • Perform additional studies if needed • Implement control measures • Communicate findings

13. Establish Existence of Epidemic • Determine if observed numbers exceed the expected level • Be aware of artifactual causes of increases or decreases of reported cases • Change in reporting practices • Change in case definition • New diagnostic test available

14. Steps of an Outbreak Investigation • Establish existence of an outbreak • Verify the diagnosis • Define a case • Identify additional cases • Perform descriptive epidemiology • Develop and test hypothesis • Reconsider hypothesis • Perform additional studies if needed • Implement control measures • Communicate findings

15. Verify the Diagnosis • Confirm clinical diagnosis with laboratory techniques • Not every reported case needs to be laboratory confirmed

16. Steps of an Outbreak Investigation • Establish existence of an outbreak • Verify the diagnosis • Define a case • Identify additional cases • Perform descriptive epidemiology • Develop and test hypothesis • Reconsider hypothesis • Perform additional studies if needed • Implement control measures • Communicate findings

17. Case Definition • Consists of standard elements • Clinical information • Time • Place • Person • Can have varying degrees of certainty • Suspect • Probable • Confirmed

18. http://www.cdc.gov/osels/ph_surveillance/nndss/casedef/measles_2010.htmhttp://www.cdc.gov/osels/ph_surveillance/nndss/casedef/measles_2010.htm

19. Case Definition • Can vary depending on the purpose • Characterize the extent of the outbreak • Determine risk factors or find a cause

20. Steps of an Outbreak Investigation • Establish existence of an outbreak • Verify the diagnosis • Define a case • Identify additional cases • Perform descriptive epidemiology • Develop and test hypothesis • Reconsider hypothesis • Perform additional studies if needed • Implement control measures • Communicate findings

21. Identify Additional Cases http://www.cdc.gov/excite/classroom/outbreak/steps.htm

22. Steps of an Outbreak Investigation • Establish existence of an outbreak • Verify the diagnosis • Define a case • Identify additional cases • Perform descriptive epidemiology • Develop and test hypothesis • Reconsider hypothesis • Perform additional studies if needed • Implement control measures • Communicate findings

23. Perform Descriptive Epidemiology • Orient data in terms of time • Orient data in terms of place • Orient data in terms of person

24. Orient by Time • Characterize the cases by plotting a graph or epidemic curve that shows • the number of cases (y-axis) • over the time of onset of illness (x-axis) using an appropriate interval

25. Epidemic Curve • Size of the epidemic • Relationship to endemic cases • Outliers • Time course • Pattern of spread • Where you are in the course of the epidemic http://www.cdc.gov/excite/classroom/legionnairesq.htm

26. Epidemic Curve of HUS CasesGermany 2011 http://www.eurosurveillance.org

27. http://www.wpro.who.int/NR/rdonlyres/7165D4BF-D820-4CB5-A1FD-267F905639D8/0/Slide1.jpghttp://www.wpro.who.int/NR/rdonlyres/7165D4BF-D820-4CB5-A1FD-267F905639D8/0/Slide1.jpg

28. Orient by Place • Geographic distribution of cases can provide clues to source of the epidemic • Water supplies • Air flow patterns in buildings • Ecologic habitat of vectors • May help identify the vehicle or mode of transmission

29. http://gamapserver.who.int/mapLibrary/Files/Maps/Global_H5N1inHumanCUMULATIVE_FIMS_20110316.pnghttp://gamapserver.who.int/mapLibrary/Files/Maps/Global_H5N1inHumanCUMULATIVE_FIMS_20110316.png

30. Orient by Person • Examine characteristics of cases • Personal characteristics • Exposures

31. http://www.wpro.who.int/sites/csr/data/data_Graphs.htm

32. Steps of an Outbreak Investigation • Establish existence of an outbreak • Verify the diagnosis • Define a case • Identify additional cases • Perform descriptive epidemiology • Develop and test hypothesis • Reconsider hypothesis • Perform additional studies if needed • Implement control measures • Communicate findings

33. Develop and Test Hypothesis • Develop hypothesis using descriptive epidemiology • Person, place and time • Clinical and laboratory findings • Test hypothesis using analytic epidemiology • Identify exposures significantly associated with illness • Analytic epidemiologic study designs • retrospective cohort study • case-control study

34. (Retrospective) Cohort Study • Enrolled after the disease has occurred • Enrolls everyone in a given population regardless of disease status • Technique of choice for acute outbreak in well-defined population • Church picnic

35. (Retrospective) Cohort Study • Directly measure risk of disease because the population at risk is known • Outcome measure is relative risk • Risk in the exposed group divided by the risk in the unexposed group (relative risk) • Also known as the attack rate ratio

36. Case-Control Study • Begins conceptually with disease and looks backward at prior exposures • Useful when the population at risk is unknown • Group of people with disease (cases) and group of people without disease (controls) are enrolled and prior exposures are ascertained • Differences in exposure between groups indicates an association between exposure and disease

37. Case-Control Study • True size of exposed and unexposed groups is unknown • No denominator to calculate attack rate or relative risk • Outcome measure is odds ratio (OR) • Odds of developing disease based on exposure • Odds ratio can approximate relative risk • When the cases are representative • When the controls are representative • When the disease being studied is rare

38. Study Design Comparison

39. Steps of an Outbreak Investigation • Establish existence of an outbreak • Verify the diagnosis • Define a case • Identify additional cases • Perform descriptive epidemiology • Develop and test hypothesis • Reconsider hypothesis • Perform additional studies if needed • Implement control measures • Communicate findings

40. Reconsider Hypothesis • “Square” the hypothesis to clinical, laboratory and epidemiologic facts • If exposure histories for ill versus well are not significantly different, develop a new hypothesis

41. Steps of an Outbreak Investigation • Establish existence of an outbreak • Verify the diagnosis • Define a case • Identify additional cases • Perform descriptive epidemiology • Develop and test hypothesis • Reconsider hypothesis • Perform additional studies if needed • Implement control measures • Communicate findings

42. Perform Additional Studies • Find more cases • Define better the extent of the epidemic • Evaluate new laboratory method • Evaluate case-finding technique • Improve sensitivity and specificity of case definition • Degrees of exposure / dose response • Environmental investigation

43. Steps of an Outbreak Investigation • Establish existence of an outbreak • Verify the diagnosis • Define a case • Identify additional cases • Perform descriptive epidemiology • Develop and test hypothesis • Reconsider hypothesis • Perform additional studies if needed • Implement control measures • Communicate findings

44. Implement Control Measures • Prevent exposure • Prevent infection • Prevent disease • Prevent death

45. Control Measures for Influenza

46. Steps of an Outbreak Investigation • Establish existence of an outbreak • Verify the diagnosis • Define a case • Identify additional cases • Perform descriptive epidemiology • Develop and test hypothesis • Reconsider hypothesis • Perform additional studies if needed • Implement control measures • Communicate findings

47. Communicate Findings • Outbreak investigation staff • Public health personnel • Government officials • Healthcare providers • Media • Community

48. Risk Communication • Developed from the need to find more effective ways to communicate health risks • Goal is to provide information about expected type and magnitude of an outcome from a behavior or exposure • The purpose of the message is to empower decision-making

49. Risk Communication Pitfalls • Mixed messages from multiple experts • Messages that are over-reassuring • Leaving myths, rumors, and doomsayers unchallenged or uncorrected • Public spokespersons who lack affect

50. http://www.bt.cdc.gov/CERC/