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The Role of Epidemiology in Public Health Practice

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Title: The Role of Epidemiology in Public Health Practice


1
The Role of Epidemiology in Public Health Practice
  • James Buehler, MD

Rollins School of Public Health Emory
University Atlanta, Georgia
Pennsylvania Public Health Institute May 28, 2004
2

June 4, 2004, 502 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
  • Epidemicsthe 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

9
(No Transcript)
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 need reliable, ongoing information 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
Desirable Attributes of Surveillance
  • Simple
  • Flexible
  • Quality data
  • Acceptable
  • Complete
  • Cases really cases
  • Representative
  • Timely
  • Stable

Source CDC. Updated Guidelines for Evaluating
Public Health Surveillance Systems. MMWR RR,
Vol. 50, y July 27, 2001.
But you cant have it alltake 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)
Admit to Hospital
Can epidemic be detected sooner?
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 upwith 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
27
(No Transcript)
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 PADOHto 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
10 Steps of a Epi Field Investigation
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
  • 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
    dont
  • How are they differentwho 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
    dont
  • How are they differentwho 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
    dont
  • How are they differentwho 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
    dont
  • How are they differentwho gets sick?

Eating a menu item containing green onions was
reported by 98 of case-patients, compared with
69 of controls (OR 20.2, 95CI 6.8--59.9).
Source CDC MMWR
39
10 Steps of a Epi Field Investigation
The Food and Drug Administration (FDA), CDC, and
the state health departments are investigating
the source of the green onionsand how they
became contaminated . Preliminary traceback
information indicates that green onionswere
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
  • 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
  • Epidemiologya discipline that produces evidence
    used in public health
  • Inform policy

43
Policy 1. a principle or course of action chosen
to guide decision making 2. prudent
management Source Websters Dictionary
44
Public Health PolicyLessons 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
  • Dont smoke cow manure
  • Stay away from active volcanoes

45
Examples of Public Health Policy (Continued)
  • Pandemic flu vaccinationSwine 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 Evidenc
e / 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 shallofficials, who are not themselves
expert, deal withpolicy questions that are
based...on highly technical and
complexknowledge--especially when that knowledge
is speculative, or hotly debated, or when the
facts are so uncertain? With how much deference
andskepticism should thosemaking 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/
50
Public Health Disciplines
  • Administration
  • Behavioral sciences
  • Communication
  • Economics
  • Epidemiology
  • Ethics
  • Environmental health
  • Evaluation
  • Health care professions
  • Geography
  • Management
  • Policy analysis
  • Statistics

51
Are you just pissing and moaning, or can you
verify what youre saying with data?
Source The New Yorker
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