1. Intn to Feild Epidemiology 2022.ppt

Introduction to Field Epidemiology
By Tilaye W[MPH, Asst. Prof. of
Epidemiology]
&
Fufa B[MPH/Field Epidemiology]
A C S H M C
March 2023
March 2023 Introduction to Feild Epidemiology 1

Outline
2
 Definition and concept of field epidemiology
 Research-related characteristics of field
investigation
 Purposes of field investigation
 Unique challenges of field investigation
 Standards of field investigation
March 2023 Introduction to Feild Epidemiology

Introduction
 Definitions of ﬁeld epidemiology (FE) have come
to the fore only recently
 ‘Application of epidemiology in the field’
 Epidemiologists work in ﬁeld settings in a variety
of contexts
 Specifically, the term Feld epidemiology
describe investigations in response to urgent
public health problems
3

4
 Public health emergencies (PHE) and the specific
responses they trigger illustrate the core aspects
of FE
 Primary goal of FE is:
– To inform, as quickly as possible, the processes of
selecting and implementing interventions to lessen
or prevent illness or death when such problems
arise
Introduction . . .

5
 FE is defined as the application of epidemiology
under the following set of general conditions:
– Timing of the problem is unexpected;
– Timely response is demanded;
– Epidemiologists must travel to and work in the
ﬁeld to solve the problem; and
– Extent of investigation is likely to be limited b/c
of the urgency for timely intervention and by
other situational constraints on study designs or
methods
Introduction . . .

• ‘Shoe leather epidemiology’ … why?
‘Field Epidemiologists are engaged in
field investigations that are sometimes
referred to as ‘shoe leather
epidemiology’, conjuring up images of
dedicated, if haggard, epidemiologists
beating the pavement in search of
additional cases and clues regarding
source and mode of transmission....’
CDC. Principles of Epidemiology.
Introduction . . .

Characteristics of FE
7
 In analytic epidemiologic studies,
– Formulating a testable hypothesis recommended
– The size of the sample matter
– The type of sampling procedure relevant
– Quality of data and possible sources of error
identified
– Detailed proposal required
– etc

8
 Field investigations (FI) share many xics with
prospectively planned epidemiologic studies
 But, FIs differ in some important aspects:
1.Start without clear hypothesis
– Use descriptive study to generate hypothesis
and follow-up analytic study to test hypotheses
2.Immediate need to protect the health of the
community
–Not confined to data collection and analysis
Characteristics . . .

9
3. Actions must be taken when data are sufﬁcient?
– No need to wait for large sample data and trying to
answer additional question is not priority
4.Dilemma of public health action versus research?
– No need of detailed proposal or protocol
– Issues of ethical review and clearance
– Exempted?
– Obtaining and documenting informed consent
• Waivered? Case-control study?

10
• Field investigations of public health emergencies
often unmask latent threats to health that have
gone unrecognized
E.g. - Food safety issues in food establishments
- Infection prevention issues in health settings
- Occupational hazards in industries
• Field investigations can prompt:
– Immediate interventions and
– Long-term recommendations

11
• Concepts and methods used in FI derived from:
– Clinical medicine
– Epidemiology
– Laboratory
– Behavioral sciences
– Decision theory
– Skills in communications
– Skills in common sense

Purposes of field investigation
12
• Health offices/bureaus may become aware of
potential disease outbreaks or other acute public
health problems from alerts and reports that come
in variety of ways:
– Clinicians can recognize and report unusual
patterns of disease
– Surveillance systems can detect increases health
events
– Members of the public could report their
suspicions or concerns

13
• Primary purpose of field investigation is:
– Implementing control measures to end threats to
the public’s health
• Other purposes include:
1.Program considerations
2.Public and political concerns
3.Research and learning opportunities
4.Legal obligations, and
5.Training needs
Purposes of FI . . .

14
1. Program Considerations
• Certain d/ses and conditions under the national or
regional surveillance system (could be targets for
eradication or elimination) have speciﬁc requirements
requirements for epidemiologic investigation
Eg. Guinea worm …
• Helps to provide timely and appropriate intervention
and to evaluate control strategies

15
2. Public and Political Concerns
• Public’s concerns can drive political process to
effect an investigation or public health action
• Can lead to premature and unproductive
investigations, but are critical in terms of community
community relations
• In some instances, a citizen’s alert can lead to
recognition of major public health problems
Eg. Lyme disease in Lyme, Connecticut, in
in 1976

16
2. Public and Political Concerns (Cont…)
• Small clusters of disease that often occur by chance
alone are common public concerns
• Often inconclusive investigations yielding new
information occasionally.
• Good to develop standard procedures for
investigating such clusters of public concerns
• Consequences could be grave if there would be
delays and real outbreaks occur

17
3.Research and Learning Opportunities
• Outbreaks are ‘natural experiments’
• Investigations can provide opportunities to:
– Identify new agents and risk factors
– Deﬁne clinical spectrum of disease
– Measure impact of new interventions
– Assess usefulness of microbiologic or other
biological markers
– Evaluate the utility of new diagnostic tests

18
3. Research and Learning (Cont…)
• Though it is uncommon, some emerging and re-
emerging d/ses are initially recognized only upon the
the occasion of an epidemic.
• Eg Legionellae pneumophilia, toxic shock syndrome,
AIDS, hantavirus pulmonary syndrome, West Nile
virus disease, and SARS.
• Some investigations can lead to important
epidemiologic discoveries – drug-resistant strains of
micro-organisms.

19
4. Legal Obligations
• Field investigations frequently require access to
some sensitive and private information of
individuals:
– Patients’ private records, queries about private
behaviors, identiﬁcation of missteps of private
enterprises putatively responsible for illness,
review of companies’ sensitive information, or
even reporting of errors of health-care
providers

20
4. Legal Obligations (Cont…)
• Joint epidemiologic and criminal investigations could
could be necessary in some situations.
• Some investigations could be used as testimony in
civil or criminal trials
– Complete, objective and defensible ﬁeld
investigation is required
– Chain of custody of evidence has to be established
established for criminal prosecutions

21
5.Training Needs
• Outbreak investigations provide opportunities for
for training in basic epidemiologic skills.
• Training in ﬁeld epidemiology is an on-job
training.
• Trainees are actively involved in the actual
delivery of disease control and prevention
interventions and at the same time they develop
develop the required skills.
• Trainees are hence called residents.

Unique Challenges of FI
• Generally, in contrast to prospectively planned
studies, epidemiologic studies during FI might not
have carefully developed and refined protocols
• There are some unique challenges and constraints.
• Major unique challenges related with FI include:
1. Data related
2. Small sample size
3. Specimen collection related
4. Impact of publicity
5. Reluctance of subjects to participate, and
6. Conﬂicting pressures to intervene

23
1. Data Source
• Field investigations could use primary or secondary
data abstracted from variety of sources (offices,
health settings, schools …).
• Not using standard, pretested questionnaires,
physical or laboratory examinations, or other
prospectively designed data collection methods will
compromise data quality (inconsistent, incomplete,
untimely, inaccurate, unreliable …).
• As much as possible, we need to employ data
verification and quality assurance techniques.
Unique Challenges of FI . . .

24
2. Small Sample Size
• Outbreaks can involve a relatively small number of
people, thereby imposing substantial restrictions on
statistical power, study design, and other aspects of
analysis
• Major limitation to make inferences and conclusions
based on the FI
• Whenever possible, we have to determine the
sample size scientifically and follow the standard
analysis plans of epidemiologic studies

25
3. Specimen Collection
• Field investigators arrive on scene ‘after the fact’.
fact’.
• Collection of necessary biological or
environmental specimens at the optimal time (like
(like acute phase) is not always possible.
– Eg. Food entirely consumed or discarded
– Water system may have been ﬂushed
– Ill persons may have recovered

26
4. Publicity
• Outbreaks often generate considerable local
attention and publicity.
• Media can help to share relevant information, in
in identification of cases, in health promotion,
and in implementation of control measures.
• On the other hand, such publicity could have
some drawbacks.

27
4. Publicity (Cont…)
• Drawbacks of publicity:
– Mass panic
– Preconception among affected persons and
community members about the source or cause of
outbreak can lead to potential biases in the studies
or a failure to fully explore alternate hypotheses.
• Regular and timely update should be provided to
all concerned thru appropriate personnel.

28
• Communications should address what is known,
what is not known, and what actions are being
taken to assess public health threats.
• Reporters may demand considerable amount of
epidemiologists’ time.
• Ensure that a member of response team has the
time and skills to communicate effectively with
reporters.

29
•During course of investigation, there could be
change and revision of information, interventions and
and recommendations.
– New information can unfold while testing,
reshaping, and re-testing hypotheses.
•Skillfully informing affected parties and the public
about the reason for changes is crucial to assure
credibility of ﬁeld epidemiologists and the
recommendations.

30
5. Reluctance to Participate
• Of course, appropriate government bodies (health
(health bureau/offices, public health institutes …)
…) are empowered to conduct investigations and
gain access to records.
• Relevant parties are expected or obliged to
participate in such investigations.
• Still, voluntary and willing participation of involved
involved parties is more conducive to successful
investigations than is forced participation.

31
5. Reluctance to Participate (Cont…)
• People whose livelihoods or interests are at risk may
may be reluctant to cooperate voluntarily.
– Eg. Food establishments, industries, health
settings
• Delays and unwillingness in participation and
investigation process can compromise access to and
quality of information.
– Random and systematic errors could arise.

32
6. Conﬂicting Pressures to Intervene
•During course of investigation, there could be
dilemma of further investigation versus action
based on the available information. Because,
– Deﬁnitive information about source, cause,
potential impact of the problem, and plausible
control measures might not be available as
early as possible
– D/nt parties including affected group and
community could have varying opinions –

33
6. Conflicting Pressures (Cont…)
• Delaying interventions may give more definitive
information, but such delays may lead to
additional morbidity/mortality
• Epidemiologists conducting field investigations
must decide and take action asap by analyzing
available information and differing opinions
• The action could be welcomed by some and
challenged by others

Standards of FI
34
• FI are sometimes perceived as ‘quick and dirty’
epidemiology b/c of inherent nature of
circumstances that need rapid responses
• By no means, the need for rapid response can
justify epidemiologic shortcuts
• Rather, combining good science with careful
judgment are crucial
• Better description of a good epidemiologic FI would
be ‘quick and appropriate’

35
• Of course, in epidemiologic FI, paramount
consideration should be given to the quality of the
science
• But, quality of the science should not be the sole
standard b/c of some inevitable limitations,
pressures and competing responsibilities
• The goal should be to maximize scientiﬁc quality of
the FI in face of the limitations and competing
interests
• So, we should consider set of standards to ensure
Standards of FI . . .

36
• Major standards of field investigation include:
1.Timeliness
2.Addresses important public health problem in
the community
– E.g. Based on attack rates, apparent or potential
serious morbidity or mortality, and community
concerns
3.Examines resource needs early and deploys
them appropriately

37
4.Employs appropriate methods of descriptive
and/or analytical epidemiology
5.Engages expertise from other disciplines, as
appropriate (microbiology, toxicology, psychology,
anthropology, informatics, or statistics)
6.Probes causality to sufficient degree to enable
identiﬁcation of source and/or etiology of the
problem.

7.Identiﬁes evidence-based options for immediate
control and long-term interventions; and
8.Is conducted in collaboration with different parties
(policy, legal, programmatic, communication, or
administrative roles) to assure evidence is used
optimally.
38

Summary
39
• What are the set of conditions that are key in defining
FE?
• What are some of the key characteristics of FI?
• What are purposes of FI?
• List major challenges of FI?
• FE is called ‘shoe leather epidemiology’; why?
• FE is perceived as ‘quick and dirty epidemiology’.
- Is this appropriate perception? Why?

e……n……d….!

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1. Intn to Feild Epidemiology 2022.ppt