International Journal of Epidemiology 2001;30:320–325
Applied epidemiology for the 21st Century
Stephen B Thacker and Joanna Buffington
Background Critics argue that the modern epidemiologist seems more concerned with intricately
modelling complex relationships among risk factors than understanding their
origins and their implications for public health. Indeed, some contend that epidemiology has reached its limits as a discipline. To address such concerns, alternatives
have been proposed that integrate biological, analytical, and social approaches to
epidemiological practice and training.
Methods
The published literature was reviewed to examine critical issues in current epidemiological practice and training. In addition, we reviewed records of training
programmes in applied epidemiology established in 20 countries.
Results
We describe an existing approach to preparing epidemiologists for the emerging
challenges of public health in which epidemiological research and practice are
applied toward the end of improving public health and health care. Training in
applied epidemiology is based on a philosophy of ‘learning while doing’. Under
the supervision of an experienced epidemiologist, trainees conduct field investigations, analyse large data bases, evaluate surveillance systems, publish and
present scientific research, and respond to public enquiries. More than 3000 people
have received intensive formal training over the past 50 years in programmes in
more than 20 countries; most graduates continued to use the tools of applied
epidemiology in their work.
Conclusion
Training in applied epidemiology anchors the discipline in population-based,
relevant public health practice.
Keywords
Epidemiology, training, public health
Accepted
1 August 2000
As the global population exceeds 6 billion people and modern
transport and technology brings people closer together, public
health challenges expand. Not only is the transmission of infectious diseases between continents a routine occurrence, but
the developed world has begun increasingly to share with the
less developed world the modern problems of environmental
pollution, tobacco-related diseases, cancer, heart disease, and
injuries. At the same time, the practice of global public health
has expanded to include a network of practising epidemiologists
working together and with other public health practitioners to
address commonly shared challenges and opportunities. In this
paper, we review the increasing concerns about the adequacy
of current training in epidemiology for public health practice.
We then describe an existing approach to preparing epidemiologists for the expanded scope of problems relevant to public
health intervention. In this approach, epidemiological research
and practice are applied toward the end of improving public
health and health care; they are not solely seen as a basis for
understanding the underlying causes of disease and health
conditions.1
Epidemiology Program Office, Centers for Disease Control and Prevention,
Mailstop C08, 1600 Clifton Road NE, Atlanta, GA 30333, USA. E-mail:
[email protected]
The 1988 report on public health in England (The Acheson
Report) concluded that academic epidemiology has limited
relevance to the everyday practice of public health in that
country.2,3 The authors of the report concluded that training in
epidemiology should remain in academia, but should be expanded
to involve projects in applied public health. In particular, the
authors contended that, in addition to methodology in statistics
and computing, the major contribution of epidemiology should
include a way of thinking which focuses on the many aspects of
life that might influence health.
In 1996, a series of articles in the American Journal of Public
Health focused on Susser’s critique of the current international
focus on risk factor epidemiology, or what Susser termed ‘the
black box paradigm’.4–8 Susser underscored the need to anchor
epidemiologists to public health and called for a practical programme to ensure that during their training epidemiologists
would be socialized to keep the improvement of the public’s
health as a primary value.7 Like the authors of the Acheson
Report, Susser underscored the need to include faculty with
experience in public health that could understand and embody
public health values. In commenting on Susser’s paper, Pearce
argued that epidemiology as a branch of public health must reintegrate itself into the practice of public health and rediscover
a population perspective.8 A second series of articles published
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APPLIED EPIDEMIOLOGY FOR THE 21ST CENTURY
in the American Journal of Epidemiology in 1997 also discussed
the failure of academic epidemiology to prepare students in the
basic science of public health by assuming (implicitly or explicitly)
that risk factors for disease in individuals could be summed
to understand the causes of diseases in populations.9,10 A third
series of articles that appeared in the Journal of Epidemiology and
Community Health in 1998 also discussed the Susser position.11–18
In that issue, Morabia argued that epidemiology has historically
found its balance in the tension between the search for causal
relations and the improvement of public health; overemphasis on
either perspective puts epidemiology at risk of losing its value.18
In 1999, a fourth collection of articles which was published in
the International Journal of Epidemiology focused on what Saracci
characterized as tensions: the tension between methods and
population health; the poles within epidemiology from the
biological to the societal; the tension between integration and
specialization; and the tension between investigator-initiated
research and research driven by population needs.19–25 In his
contribution, Pearce argued that modern epidemiology is based
on methods that are inadequate for studying population health
and that the loss of the population perspective risks limiting
epidemiology to a measurement tool for testing hypotheses
developed by other researchers.24
In all of these discussions, critics argue that the modern
epidemiologist often seems more concerned with intricately
modelling complex relationships among risk factors than understanding their origins and their implications for public health
and doing something about a problem. These critics further contend that graduate students in epidemiology focus on learning
study design and data analytical methods rather than how
to generate hypotheses regarding the social dynamics of health
and disease. This perspective is supported by a review of
the content of textbooks which highlighted the gap between
academic epidemiology and public health practice.26 This
emphasis on methodology is not new, evolving from the 1915
report that led to the formation of the Johns Hopkins School of
Hygiene and Public Health. This report emphasized a biomedical
as opposed to a sociological approach to public health.27 Criticism
of the biomedical approach is not new—McKeown has written
that the social inequalities in health are the defining problem of
the discipline of epidemiology, and the loss of this perspective
is a loss to public health.28 More recently, Terris, Gordis, and
others have discussed and debated the challenges confronting
current epidemiological practice.29–32 Both Krieger27 and Susser7
contended that epidemiology is much more than a collection of
methods. They have proposed an ecosocial framework which
integrates the biological, analytical, and social approaches and
argued that the practising epidemiologist must be as rigorous
about categories of thought as she/he is in the analysis of data.
Is, in fact, epidemiology facing its limits because of the current
approach to risk factors and methodology?33
Public health epidemiology usually traces its origins to John
Snow’s investigation of cholera in London and his successful
public health action. A much more complex history of epidemiology has been traced to others in the UK and continental
Europe.34 We describe an approach to epidemiological training
that has evolved from the approach of Snow and his contemporaries and whose trainees are anchored to public health by
mentors that are public health practitioners with a populationbased perspective.
321
Training in applied epidemiology:
the Epidemic Intelligence Service
The Centers for Disease Control and Prevention’s (CDC) Epidemic Intelligence Service (EIS) is a 2-year, on-the-job training
and service programme that provides health professionals with
an opportunity to engage, in the US and abroad, in the public
health practice of epidemiology.35,36 The programme is based
on a philosophy of ‘learning while doing’ with an emphasis on
the development of epidemiological judgement—the reasoning
process that indicates when one has sufficient data on which
to make public health decisions. Since 1951, more than 2500
professionals have served in the EIS.
Each year approximately 65 health professionals enter the
EIS programme beginning with a 3-week course oriented around
a series of epidemiological case studies, many of which are
based on investigations conducted by EIS officers. Up to 10 case
studies are complemented by interactive didactic sessions in
applied epidemiology and biostatistics as well as a field exercise
in which, over a matter of days, the officers work with local
public health officials to collect data in the field, analyse the
data, report the data in a summary manner and make recommendations regarding the findings.
During the 50 years of the EIS programme, the structure of
the introductory course has remained the same but the content
has evolved substantially. Today’s officers are presented with
case studies in infectious disease as well as chronic diseases,
injury, and bioterroism. Sophisticated analytical methods are
included in the course along with specialized training in the use
of software designed for the applied epidemiologist. The new
officers learn immediately that the EIS programme is not a
typical academic credentialing programme, rather it is a
structured experience of service and training that embodies an
approach to the learning and practice of epidemiology that is
grounded in applied public health.
During the two years of their training, the officers participate
in additional one-week courses; one on the methods of public
health surveillance and scientific communications (including
how to communicate effectively with the media) and a second
on prevention effectiveness methods (economic techniques in
public health). The essence of the EIS programme, however, is
not the coursework. Rather it is mentored experience in the
field addressing current public health challenges using the
tools of epidemiology. The hands-on training in epidemiology is
accomplished through a 2-year assignment working directly
with a CDC programme, a state or local health department, or
another federal agency. The focus for each assignment is either
in a specific programme area such as a chronic or infectious
disease or in general public health activities in a state or local
health department. In these assignments, EIS officers learn
the basic skills of epidemiology under the supervision of an
experienced, practising public health epidemiologist. During
the two years, each officer is required to complete a set of core
activities, including the conduct of field investigations, the
analysis of large data bases, the evaluation of public health surveillance systems, the publication of a scientific paper, effective
oral communications, and response to public enquiries. In these
field investigations and other activities, the officer typically
assumes lead responsibility not only for the scientific issues
but also for communication of the results of the work to local
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INTERNATIONAL JOURNAL OF EPIDEMIOLOGY
officials, the public, and the media. In addition, large numbers of
officers have taken the opportunity to participate in at least one
international experience during the 2-year programme.
Upon completion of the EIS programme, graduates are likely
to practice what they have learned in the public health system.
As of 1999, of the 2272 men and women who had completed
the programme, 129 were retired or deceased and employment
status was unavailable in 130. The current occupations of the
remaining 2013 graduates were often in public health positions
at the national level (709—35.2%) and the state and local
level (180—8.9%). In recent years, increasing numbers of EIS
graduates choose public health careers. In the decade ending
in 1987, 338 (58.8%) of the 575 graduates worked in public
health at the local, state, or national levels at a comparable time
in their careers.37 Of the 697 graduates in the classes of 1988–
1997, in 1999, 459 (66.0%) were working in public health
positions at the local, state, and national levels. In comparison,
of 86 graduates of the University of Washington from 1986
to 1996 who obtained PhD’s in epidemiology, 44 (51%) were
members of university faculties, 9 (11%) were in non-faculty
university positions, 14 (16%) were in medical institutions and 14
(16%) were in positions in national, state, or local governments.38
Since the creation of CDC in 1946, the agency has expanded
its mission from the investigation and control of communicable
diseases to include prevention programmes in chronic and
occupational diseases, injury and environmental exposures,
and their sequellae. These changes at CDC parallel a growing
international need for epidemiologists in the expanding areas of
disease and injury control in both the public and private sectors.
Through these changes, the EIS programme has had the flexibility to evolve from a team of ‘disease detectives’ with a mission
to track and protect the public from possible biological warfare
to include investigation and prevention of non-infectious diseases and injuries. Changes in the training of officers have been
implemented through their mentors in anticipation of these
changes in public health practice to include social and behavioural sciences, prevention effectiveness and informatics. In
addition, the programme has attracted new kinds of professionals. Before the 1980s nearly all EIS officers were US citizens,
and more than 90% were physicians, the remaining 10% being
mostly veterinarians, nurses, and dentists. Today, EIS officers
include increasing numbers of non-physicians with doctoral
degrees in the social and behavioural sciences as well as epidemiology.39 In addition, increasing numbers of non-US citizens
have entered the programme.
One area of increased trainee recruitment has been nonmedical, doctoral level scientists. Since 1964 more than 160
non-medical level doctoral level scientists have entered the EIS
programme, including 94 with advanced degrees in epidemiology
and others with degrees including demography, anthropology,
sociology, behavioural science, psychology, statistics, economics, and
other health-related areas.39 Nearly all of these officers came to EIS
after 1980. This recruitment was in response to changing needs at
CDC as the agency not only expanded its mission but also recognized the multi-factorial determinants of disease and injury in
all of public health. Following completion of the programme,
84% of these non-medical graduates continued to work in public
health activities with about half employed at CDC and others
either in academic institutions, state and local health departments, other federal agencies, or international health agencies.
Global training in applied epidemiology
With the growing recognition of the need for epidemiologically
trained health professionals in many countries in the past
20 years, there has been expansion of training in applied
epidemiology. Since the first non-US citizen enrolled in EIS in
1975, 174 officers have been non-US citizens; half came from
industrialized nations (Western Europe, Australia, New Zealand,
and Canada); of the 174, 17% come from Asia or the Pacific
Islands; 14% from the Caribbean, Central or South America;
10% from Eastern Europe or the Middle East; 9% from Africa.
Their entry into EIS was in recognition of the need for CDC to
help build an international epidemiological network to respond
to emerging global health issues. Most are physicians (90%).
Following EIS, 43% of these graduates work in government
agencies; 22% in academics; 14% in international agencies,
13% in private organizations, and 8% in fields outside of public
health. The majority of non-US citizens completing EIS return
either to their country of citizenship or another international
setting to work in public health areas of international scope. In
1999, 62% were working outside the US.
Epidemic Intelligence Service graduates and CDC staff have
also served as technical consultants to 19 countries aiding their
efforts to create programmes of training similar to EIS. Most of
these programmes are known as Field Epidemiology Training
Programmes (FETP), and trainees in these programmes are
citizens of the countries sponsoring the programmes.40 Beginning with Canada in 1974, and Thailand in 1981, FETP provide
training designed to build public health capabilities and infrastructure within the participating country through the development of field-trained epidemiologists competent in applying
epidemiological methods to local public health problems. As
of January 2000, approximately 900 men and women had
completed training in these programmes.
Another applied epidemiology training programme founded
on the EIS model, the European Programme for Intervention
Epidemiology Training (EPIET), was financed through a grant
from the Commission of the European communities.41 The first
cohort of EPIET fellows was enrolled in November 1995 in an
effort to create a network of professionals throughout Europe
trained to use a standard approach to applied epidemiology including field work, surveillance, applied research, communication,
and the use of epidemiological information for public health
action. The World Health Organization (WHO) has offered an
assignment in EPIET and has had a supporting role in several
FETP. In addition, in 1999 WHO initiated the Global Health
Leadership Programme in which WHO and CDC teach applied
epidemiology and management skills to WHO staff throughout
the world.
Since 1989, the Rockefeller Foundation has sponsored
international training in clinical epidemiology, the International
Clinical Epidemiology Network (INCLEN), in 20 countries.42
The Rockefeller Foundation also funded Public Health Schools
Without Walls (PHSWOW) which are the public health equivalent
of INCLEN. Three of these programmes, in Uganda, Zaire and
Vietnam, were developed with technical assistance from CDC.
Another PHSWOW was established by the Ministry of Health
and School of Public Health in Ghana. The PHSWOW were
established in part to narrow the gap between the academic
sector in these countries and the Ministries of Health.
APPLIED EPIDEMIOLOGY FOR THE 21ST CENTURY
Training in applied epidemiology has also taken the form of
short courses, usually modelled on the introductory 3-week
course for EIS officers, but adapted for different student populations. For example, since 1986, the Institut pour le Developpement d’epidemiologie de Terrain (IDEA), the Merieux
Foundation, and the National School of Public Health in France,
in consultation with CDC, have offered an intensive 3-week
course in the principles and practices of applied epidemiology to
nearly 500 students from around the world.43 Similar courses
have been conducted in the US, Europe, Asia, and Africa.
Discussion
The applied epidemiological approach of the EIS programme,
the FETP, the PHSWOW, and EPIET respond to the concerns
that the teaching of epidemiology must be anchored to public
health practice. The epidemiologist-in-training should be
supervised by experienced faculty who understand and embody
population-based public health values. Just as physicians learn
the practice of medicine as interns and residents caring for
individual patients, students in each of these programmes learn
the practice of epidemiology by addressing public health problems of communities, and through application of epidemiological judgement are expected to practice rigorous research in
a social context. Putting epidemiological research methods to
use in public health practice is a crucial orientation of applied
epidemiology.44,45 The epidemiological field investigation is a
special illustration of a training opportunity in applied public
health.46 The inclusion in the EIS programme of people with
training in behavioural and social sciences complements the
work of traditional epidemiology in pursuit of the goal of enhanced public health practice. The goal is not to make epidemiologists into social scientists or economists, rather to give
the applied epidemiologists the tools to work with experts on
other disciplines to address the public health issues that affect
human populations. The increased inclusion of non-US citizens
in the EIS programme and the establishment of training opportunities in applied epidemiology throughout the world has been
a deliberate response to the global recognition of the crucial role
of epidemiologists in public health issues.
The adaptation of a new paradigm—whether it be the
ecosocial framework of Krieger,27 the Chinese boxes of Susser,7
or some other modification—must recognize the underlying
principle that social inequalities in health remain a defining
problem for the practising epidemiologist. In the words of Rose,
‘To find the determinants of prevalence and incidence rates, we
need to study characteristics of populations, not characteristics
of individuals’.47 Epidemic Intelligence Service training and
applied epidemiology focus on active public health problems,
and the research conducted by EIS officers is driven by population needs and the desire to improve the public’s health.
Development and subsequent implementation of training
for a new paradigm in epidemiology includes a continuous
323
adaption of coursework to involve new knowledge (e.g genetics
and molecular biology), new methods such as seen in the information sciences (e.g. hand-held computers), new and more
wide-reaching communications mechanisms such as the Internet,
and the recognition of societal challenges at the local as well as
the global level. In this context of adapting to change, the
traditional tools of the applied epidemiologist (e.g. public health
surveillance) must be adapted to new technologies and new
societal norms (e.g. effect of regulations on privacy on public
health surveillance) to best serve the public’s needs. At the same
time, the gap between academic epidemiology and public health
practice must not widen further, and the training of applied
epidemiologists should be a part of the effort to close that gap.
The applied epidemiologist is by definition an activist, moving
rapidly from findings to policy, putting epidemiological knowledge to good use. Skills in communication must be an integral
part of an epidemiologist’s repertoire, as must the ability to work
in multi-disciplinary coalitions. The 21st century epidemiologist
must do all these things in addressing public concerns while
maintaining a foundation of high-quality epidemiological research
and practice.
The EIS and other training programmes in applied epidemiology demonstrate the vitality of epidemiology as a discipline. In response to the eco-social critique, these programmes
hold public health as a primary value and are anchored in
public health practice. The faculty are epidemiologists practising
in public health settings which by their nature provide a
population-based perspective. On a daily basis these trainees are
confronted with the tension between the search for causes of
disease and injury and the pressure to improve the public’s health.
They are asked to apply the modern tools of epidemiology to
public health problems that require immediate response, yet
must also apply these tools with scientific rigor in the context
of social and cultural pressures. Essential to the viability of
these training programmes is the flexibility to incorporate not
only new analytical tools and technologies, but also different
perspectives to address pressing public health issues. The entry
of social and behavioural scientists into the EIS and the
inclusion of economic methods into the training programme
illustrate this flexibility and a responsiveness that is essential
to maintaining the relevance of epidemiology to the modern
world.
In the waning years of the 20th century, the practice of
epidemiology came under serious scrutiny, from both inside
and outside the field. The limits of epidemiology, however, are
imposed primarily by perspective. If epidemiology is narrowed
to the black box of risk factor epidemiology, what we learn
and what we can contribute to the public’s health is constrained
dramatically. On the other hand, an applied approach to
epidemiology links the discipline to public health practice and
population-based research, addressing evolving global needs in
a responsible and effective manner.
324
INTERNATIONAL JOURNAL OF EPIDEMIOLOGY
KEY MESSAGES
• Training in applied epidemiology holds public health as a primary value, and training programmes are anchored
in public health practice.
• Essential to the viability of training programmes in applied epidemiology is the flexibility to incorporate new analytical
methods and integrate perspectives in social, behavioural, and economic sciences into the learning process.
• The essence of training in applied epidemiology is a 2-year field experience mentored by a practising public health
epidemiologist.
• Since 1951 more than 3000 health professionals have completed training programmes that have been established
in 20 countries.
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