The Role of Epidemiology in Public Health Practice

1. The Role of Epidemiology in Public Health Practice Rollins School of Public Health Emory University Atlanta, Georgia James Buehler, MD Pennsylvania Public Health Institute May 28, 2004

2. June 4, 2004, 5:02 PM ET WHAT IF ? BIRD FLU SPREADS IN ASIA By FLORENCE ARTMANPublished: June 4 2004 GENEVA, Switzerland, June 4 — The World Health Organization (WHO) confirmed today that an new outbreak of a “bird flu” has sickened over 1,000 people in southeast Asia. The new strain represents the combination of bird and human strains of influenza and is capable of spreading rapidly among people. WHO spokesman Dr. David Strawman noted that this represents “a major setback in international efforts to prevent avian influenza from jumping to and spreading among humans.” In Washington, DC, Secretary of Health and Human Services Tommy Thompson said that senior health officials are considering whether to recommend widespread use of a new influenza vaccine in the United States. Influenza vaccine available. A new influenza vaccine promises protection against “bird” flu. Image source: cnn.com

3. You are: Tommy G. Thompson Secretary of Health and Human Services Image source: www.hhs.gov What questions do you have for your staff and invited experts?

4. You may be • Someone who uses epidemiologic information • Someone who is asked by epidemiologists to provide information • Epidemic investigation • Ongoing public health monitoring • An epidemiologist

5. Overview • Data are not value-free • Surveillance--the epidemiology balancing act • Epidemics—the investigation toolbox • Science, evidence, epidemiology, & policy • Goals: • More informed user of epidemiology • More effective partner with epidemiologists

6. Not everything that counts can be counted, and not everything that can be counted counts. Albert Einstein Epidemiologists seek what counts by counting what can be counted.

7. Reported AIDS Cases per 100,000United States, 2001 Source: CDC 2002,http://www.cdc.gov/hiv/stats/

8. Describing Health Disparities • Benefits • Identify questions for research studies • Identify unmet needs for services • Help define priorities for resource use • Assist community advocates • Risks • Contributes to stigma, marginalization • Oversimplifies population diversity • Fosters misperception problems are not shared

10. True Statements About Disease X in Groups 1 & 2 • The difference in rates remained unchanged • The gap decreased from a 50% difference in 2000 to a 25% difference in 2003 • The rate increased 67% in Group 1 and 100% in Group 2

11. What part of the information story is most important to tell or emphasize? • What part of the information story best identifies the need or urgency for prevention or care? • Depends on values & judgement • To make sense of the numerator, you need to know something about the denominator

12. “The terrorist barriers seem to be working.” Source: The New Yorker, November 17, 2003

13. Public Health Surveillance People who manage programs to prevent or control disease needreliable, ongoinginformation about the status of that disease (or injury, disability, exposure, risk) in the population they serve. The process that epidemiologists use to collect, manage, analyze, interpret, and disseminate that information is called “surveillance.”

14. The Doctor & the Epidemiologist

15. Simple Flexible Quality data Acceptable Complete Cases really cases Representative Timely Stable Desirable Attributes of Surveillance* Source: CDC. Updated Guidelines for Evaluating Public Health Surveillance Systems. MMWR R&R, Vol. 50, y July 27, 2001. * But you can’t have it all—take your pick

16. 2 Case Definitions for Hepatitis A • Acute onset of illness with:* • Jaundice or laboratory evidence of liver dysfunction (elevated serum aminotransferase levels) AND • Discrete onset of symptoms AND • Acute-phase antibodies (IgM) to hepatitis A • Yellow eyes * CDC. Case Definitions for Infectious Conditions Under Public Health Surveillance. MMWR 1997; 46(RR10);18

17. Change in trend monitored through surveillance : • Change in surveillance procedure • Change in surveillance resources • Change in health care practice • Change in screening program • Change in interest in condition • Change in incidence

18. New York Times, Jan 26, 2004

19. How will the next BT attack be detected? • Overt attack • Environmental sampling • Health care provider notices something unusual (increase in illness, cluster of cases, severe clinical pattern) & CALLS HD • Incidental--Routine evaluation & testing • Surveillance detects unusual trend • Tradition case reporting • “Syndromic surveillance”

20. Timeline of Bioterrorism Disease Attack Severe disease Early disease (less severe) Can epidemic be detected sooner? Admit to Hospital Diagnosis • Challenges: • Balance timelines & sensitivity with false alarms • Identifying illness of public health importance Report to Health Dept.

21. Possible Data Sources • Stay home - Absentee records • Buy facial tissue – Grocery store purchases • Buy over-the-counter medicine – Pharmacy records • Call doctor or nurse – Call logs • Primary care visit – Insurance claims, Electronic Medical Record • Emergency Room – ER logs, triage or discharge data • Antibiotic prescription – Pharmacy records, claims • Lab test done – Laboratory requisitions • Call 911, Emergency Medical Service - EMS logs • Admit to hospital - Hospital admission records • Admit to ICU – ICU logs • Death – Electronic death certificate, Medical examiner

22. New York City Department of Health and Mental Hygiene, 2002, Health Alert #37 Source: NYCDoHMH http://www.nyc.gov/html/doh/html/cd/02md37.html

23. Epidemic Investigations Hepatitis A Image source: http://phil.cdc.gov/

24. Pennsylvania Hepatitis Outbreak, 2003 The first five patients who showed up…with signs of hepatitis A infection piqued Dr. Marcus Eubanks' curiosity. But it was only when the sixth patient arrived on Friday that someone -- the patient's wife -- uttered the magic word: [Restaurant A]. The woman told Eubanks, an emergency physician… that three of the couple's friends had come down with the disease that week and that the friends had shared a meal in October at the restaurant… "He said to me, 'Oh, my God, we've got to call the Health Department,' " recalled the woman…,"We realized, 'Holy Cow, this is an outbreak.' " Source: Pittsburgh Post-Gazette

25. 10 Steps of a Epi Field Investigation • Determine the existence of the epidemic • Confirm the diagnosis • Define a case and count cases • Determine who is at risk of becoming ill • Develop and test a hypothesis that explains the exposure that caused disease • Compare the hypothesis with established facts • Plan a more systematic study • Prepare a written report • Execute control & prevention measures Gregg MB. Field Epidemiology, 2nd ed. Oxford Univ Press 2002

26. PENNSYLVANIA DEPARTMENT OF HEALTH HEALTH ALERT #61 To: Health Alert Network  From: Calvin B. Johnson, M.D., M.P.H.  Secretary of Health  Date: November 3, 2003  Subject:Large Outbreak of Restaurant-Associated Hepatitis A Source: http://www.dsf.health.state.pa.us

28. 10 Steps of a Epi Field Investigation • Determine the existence of the epidemic • Confirm the diagnosis • Define a case and count cases • Determine who is at risk of becoming ill • Develop and test a hypothesis that explains the exposure that caused disease • Compare the hypothesis with established facts • Plan a more systematic study • Prepare a written report • Execute control & prevention measures An alert clinician contacted PADOH…to report an IgM-positive hepatitis A case, and noted that as many as 10 other cases of hepatitis had been seen recently in a local Emergency Department. Source: PA DoH

29. 10 Steps of a Epi Field Investigation • Determine the existence of the epidemic • Confirm the diagnosis • Define a case and count cases • Determine who is at risk of becoming ill • Develop and test a hypothesis that explains the exposure that caused disease • Compare the hypothesis with established facts • Plan a more systematic study • Prepare a written report • Execute control & prevention measures Over the next 36 hours, additional probable cases were identified based on symptoms, and 7 other IgM-positive cases were reported. Source: PA DoH

30. 10 Steps of a Epi Field Investigation • Determine the existence of the epidemic • Confirm the diagnosis • Define a case and count cases • Determine who is at risk of becoming ill • Develop and test a hypothesis that explains the exposure that caused disease • Compare the hypothesis with established facts • Plan a more systematic study • Prepare a written report • Execute control & prevention measures All but one community case of hepatitis A interviewed so far had a single common risk factor, eating at [Restaurant A] in early October. Source: PA DoH

31. Source: CDC MMWR

32. 10 Steps of a Epi Field Investigation • Determine the existence of the epidemic • Confirm the diagnosis • Define a case and count cases • Determine who is at risk of becoming ill • Develop and test a hypothesis that explains the exposure that caused disease • Compare the hypothesis with established facts • Plan a more systematic study • Prepare a written report • Execute control & prevention measures No single food item has been implicated, and one hypothesis is that an ill food worker inadvertently contaminated multiple food items during preparation or serving. Source: PA DoH

33. The Department of Agriculture sent an inspector to the restaurant…; the inspector found no sanitary violations and emphasized strict hygiene… The restaurant corporate office has voluntarily closed the facility. A state health center clinic is being arranged to administer immune serum globulin (ISG) to well restaurant workers. A press release which includes the address of the clinic will be released shortly. Source: CDC MMWR 10 Steps of a Epi Field Investigation • Determine the existence of the epidemic • Confirm the diagnosis • Define a case and count cases • Determine who is at risk of becoming ill • Develop and test a hypothesis that explains the exposure that caused disease • Compare the hypothesis with established facts • Plan a more systematic study • Prepare a written report • Execute control & prevention measures

34. 10 Steps of a Epi Field Investigation • Determine the existence of the epidemic • Confirm the diagnosis • Define a case and count cases • Determine who is at risk of becoming ill • Develop and test a hypothesis that explains the exposure that caused disease • Compare the hypothesis with established facts • Plan a more systematic study • Prepare a written report • Execute control & prevention measures

35. Epidemiologists Make Comparisons • People who are sick versus people who are not sick • How are they different--exposures, behaviors, etc? • People who have an exposure versus those who don’t • How are they different—who gets sick?

36. Epidemiologists Make Comparisons • People who are sick versus people who are not sick • How are they different--exposures, behaviors, etc? • People who have an exposure versus those who don’t • How are they different—who gets sick? A case-patient was defined as a person who had illness onset during October 14--November 12, had laboratory confirmation of acute hepatitis A virus (HAV) infection (i.e., positive IgM anti-HAV), reported eating food prepared at Restaurant A during October 3--6, and had eaten only once at Restaurant A during the 2--6 weeks before illness onset. Source: CDC MMWR

37. Epidemiologists Make Comparisons • People who are sick versus people who are not sick • How are they different--exposures, behaviors, etc? • People who have an exposure versus those who don’t • How are they different—who gets sick? Controls included persons without hepatitis A who either had dined with case-patients at Restaurant A or were identified through credit card receipts as having dined at Restaurant A during October 3--6. Controls with a previous history of hepatitis A, hepatitis A vaccination, or receipt of immune globulin within 2 weeks after eating Restaurant A food were excluded. Source: CDC MMWR

38. Epidemiologists Make Comparisons • People who are sick versus people who are not sick • How are they different--exposures, behaviors, etc? • People who have an exposure versus those who don’t • How are they different—who gets sick? Eating a menu item containing green onions was reported by 98% of case-patients, compared with 69% of controls (OR = 20.2, 95%CI = 6.8--59.9). Source: CDC MMWR

39. The Food and Drug Administration (FDA), CDC, and the state health departments are investigating the source of the green onions…and how they became contaminated… . Preliminary traceback information indicates that green onions…were grown in Mexico. FDA issued an alert to consumers about the recent hepatitis A outbreaks associated with green onions. FDA advised consumers concerned about the possibility of getting hepatitis A from green onions to cook green onions thoroughly before eating and to ask about use of green onions in prepared foods. Source: CDC MMWR 10 Steps of a Epi Field Investigation • Determine the existence of the epidemic • Confirm the diagnosis • Define a case and count cases • Determine who is at risk of becoming ill • Develop and test a hypothesis that explains the exposure that caused disease • Compare the hypothesis with established facts • Plan a more systematic study • Prepare a written report • Execute control & prevention measures

40. Jesus Flores, proprietor of Los Baby's Fruit and Vegetable Stand in Mexicali, wants to know why Mexican farm workers are not affected by hepatitis A virus if the produce they handled allegedly is the source of infection in the United States. Source: http://www.post-gazette.com/pg/03328/243293.stm

41. Role of epidemiology in this outbreak • Identify restaurant as site of exposure • Identify green onions as likely food source • Food not contaminated by restaurant process • Sanitation experts: Restaurant inspection • Epi: Similar pattern in other states & restaurants • Trigger further environmental investigation: food “trace-back” • ? Close restaurant (policy) • Based on guidelines set in advance • Based on evidence in this situation

42. What is the role of epidemiology in public health practice? • Need to step back: What is the role evidence? • Information collected and assessed using tools of science • Epidemiology—a discipline that produces evidence used in public health • Inform policy

43. Policy1. a principle or course of action chosen to guide decision making 2. prudent management Source: Webster’s Dictionary

44. Public Health Policy:Lessons from 1981 CDC EIS Conference • Restaurant and health care workers should wash their hands • Thoroughly clean surgical instruments • Prepare & store food appropriately • Remove a particular tampon from market • Keep sewage out of drinking water • Don’t smoke cow manure • Stay away from active volcanoes

45. Examples of Public Health Policy (Continued) • Pandemic flu vaccination—Swine flu • Promotion of healthy lifestyle • Smoking cessation • Diet & exercise • Seat belts & motorcycle helmet use • HIV & STD prevention • Abstinence-only vs. comprehensive sex education • Harm reduction: Needle/syringe exchange for HIV prevention

46. Public health policy: The plot thickens • Scientific uncertainty • “We need more data…” • Competing values • Moral, ethical, religious, cultural… • Limited resources • Setting priorities • The role of government • Federal, state, local • Government, business, families, faith groups, NGOs, CBOs…

47. Requisites for Effective & Sustainable Policy Judging the value of our purpose SUBSTANCE Evidence / Science Assuring our capabilities for achieving our desired purpose ADMINISTRATION Fiscal, Human and Other Resources Investing our purpose with legitimacy and support POLITICS Executive, Legislature, Media, Public, Constituents Adapted from Mark Moore, Creating Public Value, Strategic Management in Government, Harvard Univ Press, 1995. Courtesy of Lydia Ogden MPP, CDC

48. “How shall…officials, who are not themselves expert, deal with…policy questions that are based...on highly technical and complex…knowledge--especially when that knowledge is speculative, or hotly debated, or when “the facts” are so uncertain? With how much deference and…skepticism should those…making policy view..the scientists and experts?” Joseph A Califano, Jr. Secretary, DHEW, 1978

49. Did they ask the right questions? What about study bias? Did they pick the right comparison group? Epidemiology What are the strengths & limits of the study? Do the findings make sense? Are the findings appropriately interpreted? Image source: http://www.mtholyoke.edu/

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