Defining Field Epidemiology

Introduction

Although epidemiologists work in field settings in different contexts, the term field epidemiology as used in this manual describes investigations initiated in response to urgent public health problems. A primary goal of field epidemiology is to guide, as quickly as possible, the processes of selecting and implementing interventions to lessen or prevent illness or death when such problems arise. Despite continuing changes in the contexts within which epidemiologists operate, as well as the types and quantity of information that epidemiologists have at their disposal, the core principles of field epidemiology remain largely constant.

The constellation of problems faced by epidemiologists who investigate urgent public health problems shapes the definition of field epidemiology. For example, consider the following scenario: At 8:30 am on Monday, August 2, 1976, Dr. Robert B. Craven, an Epidemic Intelligence Service (EIS) officer assigned to the Center for Disease Control's (CDC) Viral Diseases Division, received a telephone call from a nurse at a veterans' hospital in Philadelphia, Pennsylvania. The nurse reported two cases of severe respiratory illness (including one death) in persons who had attended the recent American Legion Convention in Philadelphia. Subsequent conversations with local and state public health officials revealed that 18 persons who had attended the convention during July 21–24 had died during July 26–August 2, primarily from pneumonia. By the evening of August 2, an additional 71 cases had been identified among Legionnaires. As a consequence of this information, a massive epidemiologic investigation was immediately initiated that involved local, state, and federal public health agencies. This problem became known as the outbreak of Legionnaires' disease, and the investigation of the problem led directly to discovery of the bacterial pathogen, Legionella pneumophila, 12enabling further studies of the nature and modes of transmission of this organism, the epidemiology, and natural history of Legionella infections, as well as more precise recommendations for prevention and treatment.

The Legionnaires' disease outbreak and the public health response it triggered illustrate the raison d'être for field epidemiology. Using this epidemic as an example, we can define field epidemiology as the application of epidemiology under the following general conditions:

• The timing of the problem is unexpected.
• A timely response is demanded.
• Public health epidemiologists must travel to and work in the field to solve the problem.
• The extent of the investigation is likely to be limited because of the imperative for timely intervention and by other situational constraints on study designs or methods.

Although field investigations of acute problems share many characteristics with prospectively planned epidemiologic studies, they differ in at least three important aspects.

• Because field investigations often start without specific hypotheses about the cause or source of disease, they require the use of descriptive studies to generate hypotheses before analytic studies can be designed and conducted to test these hypotheses.
• As noted previously, when acute problems occur, an immediate need exists to protect the community's health and address its concerns. These responsibilities drive the epidemiologic field investigation beyond the confines of data collection and analysis and into the realm of public health policy and action.
• Field epidemiology forces the epidemiologist to consider when the findings are sufficient to take action rather than to ask what additional questions might be answered by additional data collection or analyses or, alternatively, to take initial actions that might be modified as additional information is obtained through further investigation.

Although the timing of acute public health problems that prompt field investigations is typically unexpected, emergencies often unmask latent threats to health that had gone unrecognized or had been "waiting to happen." For example, sporadic or epidemic illness might be inevitable if restaurants fail to adhere to food management guidelines, if hospitals fail to properly sterilize instruments, if employers fail to maintain workplace safety standards, or if members of social networks engage in unsafe sexual behaviors. As a result, field investigations can prompt both immediate interventions and longer term recommendations, or they can identify problems that require further study after the immediate problem has been addressed.

Experiences during 2014–2016 with the Ebola virus disease (EVD) outbreak in West Africa underscore how networks of professionals trained in the basics of field epidemiology can play key roles in mitigating the health and economic effects of emerging disease threats, such as EVD. When left unchecked in many locations in West Africa, the EVD outbreak resulted in more than 28,000 cases and 11,000 deaths34. However, in July 2014, when a case of EVD was introduced into Nigeria, epidemiologists, in close partnership with the Ministry of Health, nongovernmental organizations, and other community members, conducted rapid field investigations to prevent further transmission5. Given the population size of Nigeria, timely epidemiologic response might have helped to avert a considerably larger disaster.

The concepts and methods used in field investigations derive from clinical medicine, epidemiology, laboratory and behavioral sciences, decision theory, an expanding array of other scientific disciplines, skill in communications, and common sense. In this manual, the guidelines and approaches for conducting epidemiologic field investigations reflect the urgency of discovering causative factors, use of evolving multifaceted methods, and need to make timely practical recommendations.

Determinants for Field Investigations

Health departments become aware of possible disease outbreaks or other acute public health problems in different ways. Situations might gain attention because astute clinicians recognize unusual patterns of disease among their patients and alert health departments, surveillance systems for monitoring disease or hazard trends detect increases, the diagnosis of a single case of a rare disease heralds a broader problem or potential threat, or members of the public are concerned and contact authorities.

After such alerts, the first step is to decide whether to conduct a field investigation. Initial assessments might dispel concerns or affirm that further investigation is warranted. After initiated, decisions must be made at successive stages about how far to pursue an investigation. These decisions are necessary to make the most effective use of public health resources, including capacities to conduct field investigations and optimize opportunities for disease prevention.

In addition to the need to develop and implement control measures to end threats to the public's health, such as the Legionnaires' disease and EVD outbreaks, other determinants that shape field investigations include (1) epidemiologic, programmatic, and resource considerations; (2) public and political considerations; (3) research and learning opportunities; (4) legal obligations; and (5) training needs.

Epidemiologic, Programmatic, and Resource Considerations

Certain disease control programs at national, state, and local levels have specific and extensive requirements for epidemiologic investigation. For example, as part of the measles elimination effort in the United States, a measles outbreak is defined as a chain of transmission including three or more cases linked in time and space6. Accordingly, every case of measles might be investigated to identify and vaccinate susceptible persons and to evaluate other control strategies, such as the exclusion from school of children who cannot provide proof of vaccination. This recommendation reflects the epidemiology of measles in the United States, where most cases result from travel-related introduction of measles into the country and where vaccination programs have dramatically reduced the incidence of measles although pockets of vulnerability to transmission remain.

Additional situations in which investigations are likely to be initiated after the diagnoses of individual cases include the emergence of highly pathogenic infections, such as influenza A(H5N1) and A(H7N9) in Asia and Middle East respiratory syndrome coronavirus. Given past experiences with influenza pandemics and severe acute respiratory syndrome (SARS), detection of such events have prompted multiple field investigations. The diagnoses of individual illnesses that might be associated with bioterrorism also should prompt investigations, at least to the point of dismissing concerns that exposure resulted from an intentional act. For example, diagnosis of a case of inhalation anthrax in a photo editor for a national media company in 2001, an occupation not associated with exposure to naturally occurring anthrax, was the first of 22 cases of terrorism-related anthrax and five associated deaths that were exhaustively investigated 7and led to massive increases in investments in public health emergency preparedness in the United States. The anthrax attacks and other bioterrorism-related concerns brought about a lowering of the threshold of suspicion necessary for triggering a full field investigation89.

Different clinical, laboratory, and surveillance technologies have the potential to enhance recognition of situations that merit investigation, including detection of individual cases of disease that might signal a larger threat to public health, early detection of disease outbreaks, or detection of environmental hazards that can result in widespread disease. Conversely, the potential benefits of these technologies might be offset by increasing the likelihood of detecting situations that do not represent public health threats yet require time and resources to draw that conclusion. At the individual level, the advent of multipathogen detection platforms also enables the simultaneous detection of multiple viruses and bacteria in a single clinical specimen. Although this technology can provide important clinical health benefits, it can challenge efforts to distinguish pathogens that are potentially related to disease outbreaks versus organisms that are merely commensal10. At the outbreak level, the advent of highly automated public health surveillance systems that incorporate statistical algorithms to detect unusual trends can provide an early warning for the onset of outbreaks as well as statistical aberrations that do not herald substantial threats11. At the level of environmental monitoring, debates surrounding proposed enhancements in the pathogen monitoring capacities of the US BioWatch system for detecting airborne biological hazards included consideration of the potential for more frequent alerts resulting from the detection of naturally occurring microbes that do not represent substantial public health threats12.

Global disease elimination and eradication programs, international preparedness and coordination for emerging threats, and advances in surveillance and laboratory technologies have helped to strengthen public health. However, these developments also place new pressures on epidemiology program managers to prioritize resources. Any expenditure of public resources should be judicious. Field investigations can be costly in personnel time and other resources and can incur opportunity costs by detracting from other public health activities. In addition, field investigations consume the time and effort of persons investigated and of persons whose collaboration is often essential. Thus, the capacity to conduct field work can be limited not only by the resources or capacity of individual public health agencies, but also by competing demands of other programs within an agency or by other situational demands. Resource constraints also might shape the extent to which investigations are conducted. In the United States, state health departments might help local governments when needed, and state or local health departments might request assistance from the CDC when their capacities are exceeded by the demands of an event. Globally, the World Health Organization and its network of regional offices serve as resources to national governments.

Public and Political Considerations

Scrutiny from the public, political leaders, and the media can occur at all stages of field investigations, including the stage when initial assessments are conducted to determine whether a field investigation is warranted. This scrutiny can affect the perceived urgency of a situation or the perceived need for investigations. The importance that others attach to problems and the conclusions that others draw from initial knowledge of situations might differ from or align with the positions of epidemiologists responsible for conducting field investigations or those of more senior public health officials responsible for determining when field investigations should be started.

In certain instances, a citizen's alert can lead to recognition of a major public health problem, such as with Lyme disease in Lyme, Connecticut, in 197613. In other cases, however, public concerns and attendant pressures might lead to investigations that otherwise are premature or unlikely to be fruitful from a scientific perspective but are critical in terms of community relations. Small clusters of disease (e.g., leukemia or adverse fetal outcomes) are an example of problems that frequently generate substantial public concern. Perceived clusters of disease might prove to represent unrelated events after formal scrutiny; small clusters of disease might occur by chance alone, and field investigations are often inconclusive and only occasionally yield new information about etiologic links to putative exposures14. However, because community members might perceive a health threat, and certain clusters do represent specific preventable risks, some public health agencies have developed standard procedures for investigating such clusters even though the likelihood of identifying a remediable cause is low15.

Determining how long an investigation should be continued can become a matter of public controversy. A decision to postpone interventions pending completion of thorough epidemiologic investigations might be perceived as community experimentation or bureaucratic delay. For example, in a large Escherichia coli enteric disease outbreak at Crater Lake National Park, Oregon, in 1975, a 1-day delay in implementing control measures to obtain more definitive epidemiologic data resulted in a Congressional hearing and charges of a cover-up16.

Research and Learning Opportunities

Because almost all outbreaks are "natural experiments," they present opportunities to address questions of importance both to basic scientists and to persons in the applied science of public health practice. Even when a clear policy exists for control of a specific problem, investigation can still provide opportunities to identify new agents and risk factors for infection or disease, define the clinical spectrum of disease, measure the effect of new control measures or clinical interventions, assess the usefulness of microbiologic or other biological markers, or evaluate the utility of new diagnostic tests.

Recognition of newly emergent or reemerging diseases often prompts aggressive investigations because of the potential for extensive, life-threatening illness. Certain diseases are initially recognized only on the occasion of an epidemic, although subsequent investigations and studies enable retrospective diagnosis of earlier occurrences, as well as more complete characterization of the spectrum of clinical manifestations and epidemiology. For example, as referred to earlier, after L. pneumophilia was discovered and a serologic test developed, subsequent studies showed that, in addition to the severe illness manifest in the 1976 Philadelphia outbreak, Legionella infection commonly results in mild disease or asymptomatic infection. Often, when new diseases are detected, they are recognized in their most severe or distinctive stage, followed later by recognition of a broader spectrum of illness. The initial recognition of certain other problems—such as toxic shock syndrome, influenza A(H1N1)pdm09, AIDS, Hantavirus pulmonary syndrome, West Nile virus disease, and SARS—was followed by aggressive investigations that enabled analogous understanding of the natural history and disease spectrum of these infections. One caveat is that dramatic outbreaks and investigations that identify previously unrecognized pathogens and that yield a wealth of new scientific insights are unusual; more commonly, field investigations of outbreaks identify familiar pathogens and modes of transmission. Yet, even for familiar diseases and modes of exposure or transmission, investigations are warranted to interrupt outbreaks and understand the evolving context in which outbreaks occur. For example, the changing prevalence of underlying conditions (e.g., obesity, diabetes, and cardiovascular disease) among the US population and demographic characteristics (e.g., cultural determinants and age) of the population have the potential to alter host susceptibility and, indeed, the epidemiologic consequences of exposure to pathogens and other hazards.

Certain outbreaks that initially appear to be routine might lead to important epidemiologic discoveries. For example, in 1983, investigators pursued a cluster of diarrhea cases, an extremely common problem, to extraordinary lengths17. As a result, the investigators were able to trace the chain of transmission of a unique strain of multiply antibiotic-resistant Salmonella back from the affected persons to hamburger they ate, to the meat supplier, and, ultimately, to the specific animal source herd. This investigation played a key role in clarifying the link between antibiotic use in the cattle industry and subsequent antibiotic-resistant infection in humans.

Legal Obligations

Field investigations frequently require access to patients' private medical records, queries about private behaviors, analyses of private enterprises putatively responsible for illness-causing exposures, reviews of proprietary information, or assessments of reported putative errors of healthcare providers or health product manufacturers. These tasks may be necessary to complete an objective, defensible field investigation, but each is also fraught with considerable ethical and legal overtones (see Chapter 13).

Findings from some investigations are likely to be used as testimony in civil or criminal trials18. In these situations, investigations might be carried further than they otherwise would be. For example, investigations in situations where criminal actions might be suspected to have played a role 19might carry additional legal requirements for establishing a chain of custody of evidence, which is necessary for criminal prosecutions. The anthrax attacks during fall 2001 and related concerns about bioterrorism have stimulated other advanced and carefully designed legal measures to facilitate joint epidemiologic and criminal investigations. An example of such measures is a protocol developed by the New York City Department of Health and Mental Hygiene, New York City Police Department, and Federal Bureau of Investigation to guide in the interviewing of patients during joint investigations by public health and law enforcement professionals representing those agencies20. Similar collaborations exist at the federal level21.

Training Needs

By analogy to clerkships in medical school and postgraduate residencies, outbreak investigations provide opportunities for training in basic epidemiologic skills. Just as clinical training often is accomplished at the same time patient care is delivered, training in field epidemiology often simultaneously assists in developing skills in and the delivery of disease control and prevention. For example, since 1951, CDC's EIS Program has provided assistance to state and local health departments while simultaneously training health professionals in the practice of applied epidemiology2223. Changes in the epidemiologic capacities of state and local health departments 24also highlight the need for workforce training and education on an expanded set of skills, such as bioinformatics, health economics, communications, systems thinking, and laboratory techniques. Globally, more than 70 Field Epidemiology Training Programs have been modeled after EIS but are owned by individual countries and ministries of health. These Field Epidemiology Training Programs provide similar on-the-job training but within the context of specific cultures, partners, capacities, and public health systems25.

Unique Challenges to Epidemiologists in Field Investigations

An epidemiologist investigating problems in the field faces unique challenges that sometimes constrain the ideal use of scientific methods. In contrast to prospectively planned studies, which generally are based on carefully developed and refined protocols, field investigations must rely on data sources that are immediately available, less readily controlled, and subject to change with successive hours or days. In addition to possible limitations in data sources, factors that pose challenges for epidemiologists during field investigations include sampling considerations, availability of specimens, effects of publicity, reluctance of persons to participate, and conflicting pressures to intervene. New technologies hold the promise of mitigating some of these challenges.

Data Sources

Field investigations often use information abstracted from different sources, such as hospital, outpatient medical, or school health records. These records vary substantially in completeness and accuracy among patients, healthcare providers, and facilities because entries are made for purposes other than conducting epidemiologic studies. Moreover, rapid and substantive transitions have occurred for several key information sources—as, for example, in the growing use of electronic medical records, hospital and managed-care data systems, and laboratory information management systems. These automated systems can facilitate access to needed records but might not be compatible with meeting the needs of or supporting specific record access by external investigators. Thus, the quality of such records as sources of data for epidemiologic investigations can be substantially less than the quality of information obtained when investigators can exert greater control through the use of standardized, pretested questionnaires; physical or laboratory examinations; or other prospectively designed, rather than retrospective, data collection methods. These transitions necessitate that epidemiologists involved in field investigations increasingly might need to know how to use these data sources and, therefore, possess the requisite skills needed to analyze them.

The increasing use of social media and email can facilitate outreach to and queries of persons who might have common exposures in an outbreak situation, such as participants in an organized event linked to a common-source exposure. Recently, social media networks have been used to assist in identifying contacts of persons with sexually transmitted diseases who might be at high risk and should be considered for targeted prophylaxis. These communication tools have provided added insight into social links and high-risk behaviors and have been used to guide and augment data collected from traditional case investigation methodologies26.

Small Numbers

In a planned prospective study, the epidemiologist determines appropriate sample sizes that are based on statistical requirements for power to draw conclusions about associations between exposures and health outcomes. In contrast, outbreaks can involve a relatively small number of persons, thereby imposing substantial restrictions on study design, statistical power, and other aspects of analysis. These restrictions, in turn, place limitations on the inferences and conclusions that can be drawn from a field investigation. However, communication technologies between jurisdictions can now be used to help alleviate this problem. For example, the electronic Epidemic Information Exchange (Epi-X) was developed for CDC officials, state and local health departments, poison control centers, and other public health professionals to access and share preliminary health surveillance information27. Although a primary motivation for this system was to enhance the recognition of multistate events or the multistate dispersion of persons with disease exposures in a single state or outside the United States, the resulting cross-jurisdictional collaboration has the additional benefit of increasing potential sample sizes for field investigations.

Specimen Availability

Because the field investigator usually arrives on the scene after the fact, collection of necessary environmental or biological specimens is not always possible. For example, suspected food items might have been entirely eaten or discarded, a suspected water system might have been flushed, or ill persons might have recovered, thereby precluding collection of specimens during the acute phase of illness when certain tests are most likely to be informative. Under these conditions, the epidemiologist depends on the diligence of healthcare providers who are first to evaluate the affected persons and on the recall of affected persons, their relatives, or other members of the affected community.

This challenge increasingly is counterbalanced by expanding technologies in the laboratory to help in using routinely collected specimens to determine sources of outbreaks. For example, PulseNet is a national laboratory network that enables the use of DNA fingerprinting to detect thousands of local and multistate outbreaks28, thereby enabling epidemiologists to rapidly implement control measures for food safety problems that would not otherwise be recognized. As another example, in 2015, epidemiologists investigated the largest HIV outbreak in the United States since 1996. Phylogenetic analyses of target genes within the human immunodeficiency and hepatitis C viruses enabled epidemiologists to retrospectively determine and intervene in the link between specific outbreak strains and local needle-sharing networks using contaminated equipment29.

Effects of Publicity

Acute disease outbreaks often generate considerable local attention and publicity. In this regard, media coverage can assist the investigation by helping to develop information, identify cases, or promote and help implement control measures. Conversely, such publicity can cause affected persons and others in the community to develop preconceptions about the source or cause of an outbreak, which in turn can lead to potential biases in comparative studies or failure to fully explore alternate hypotheses.

As government employees, field epidemiologists are obligated to communicate with the public about what is known, what is unknown, and what actions are being taken to assess public health threats. Many reporters, in turn, endeavor to find and bring this information to the public's attention. That said, reporters in pursuit of the most current information on the investigation can demand a considerable amount of epidemiologists' time to the detriment of the field investigation itself. Ensuring that a member of the response team has the time and skills to communicate effectively with reporters can be essential to the success of a field investigation and to disease control and prevention efforts, particularly in high-profile situations. Frequently during the course of an event, as information unfolds and as field epidemiologists test, reject, or accept and reshape and retest hypotheses, recommendations for interventions might evolve or become more focused. Apprising affected parties and the public of the rationale for these changes is important to ensure the credibility of the field epidemiologists and of public health recommendations (see Chapter 12).

In recent years, CDC and other public health agencies have used social media tools to disseminate health messages. Although unskilled use of this medium during an ongoing investigation can pose challenges, such as spreading misperceptions or fostering information biases, social media also can be an effective means for expanding the reach of pertinent evidence-based health messages30.

Reluctance to Participate

Although health departments are empowered to conduct investigations and gain access to records, voluntary and willing participation of involved parties (e.g., case-patients, persons potentially exposed to pathogens, owners or operators of settings in which exposure or transmission might have occurred) is more conducive to successful investigations than compelled participation. In addition, persons whose livelihoods or related interests are at risk might be reluctant to cooperate voluntarily. This reluctance often can be the case for common-source outbreaks associated with restaurants and other public establishments, in environmental or occupational hazard investigations, or among healthcare providers suspected as being sources for transmission of infectious diseases, such as hepatitis B. When involved parties do not willingly cooperate, delays can compromise access to and quality of information (e.g., by introducing bias and by decreasing statistical power).

Conflicting Pressures to Intervene

Epidemiologists who conduct field investigations are often working in a fishbowl-type of environment. Epidemiologists conducting field investigations and the public health officials under whose direction they work must weigh the need for further investigation against the need for immediate intervention, often in the face of strong and varying opinions of affected persons and others in the community. In the absence of definitive information about the source, cause, or potential impact of a problem, the various parties affected by a particular situation might view implementation of a plausible control measure differently. The action might be welcomed by those who favor erring on the side of protecting health and challenged by those who question the rationale for interventions absent definitive information about the cause or source of illness, particularly if their economic or other personal interests are threatened. Delaying interventions might allow time to obtain more definitive information, but such delays also might lead to additional illness. Although this dilemma is not unique to field epidemiology within the realm of public health practice, the heightened urgency of acute situations can elevate the emotional impact on all involved parties.

Standards For Epidemiologic Field Investigations

Field investigations are sometimes perceived to represent what is sometimes called "quick and dirty" epidemiology. This perception might reflect the inherent nature of circumstances for which rapid responses are required. However, these requirements for action do not justify epidemiologic shortcuts. Rather, they underscore for the field epidemiologist the importance of combining good science with prudent judgment. A better description of a good epidemiologic field investigation would be "quick and appropriate."

In judging an epidemiologic field investigation, consideration should be given to the quality of the science, opportunities and constraints that shaped the context of the investigation, and judgment applied in using the findings to take public health actions. The goal should be to maximize the scientific quality of the field investigation in the face of the full range of limitations, pressures, and responsibilities imposed on the investigator(s). Thus, the standards for an epidemiologic field investigation are that it 1is timely; 2addresses an important public health problem in the community, as defined by standard public health measures (e.g., attack rates, apparent or potential serious illness, or death) or community concern; examines 3resource needs early and deploys them appropriately; 4uses appropriate methods of descriptive and/or analytic epidemiology that make optimal use of all appropriate available data; 5engages expertise, when indicated, from other public health sciences, such as microbiology, toxicology, psychology, anthropology, informatics, economics, laboratory sciences, or statistics; 6probes causality to enable identification of the source and/or etiology of the problem; 13 7identifies evidence-based options for immediate control and long term interventions; and 8is conducted in active collaboration with colleagues who have policy, legal, programmatic, communication, or administrative roles to ensure that the evidence from the investigation is used optimally.

Conclusion

This chapter has provided a definition of and framework for field epidemiology in a modern and evolving context. Key developments in public health practice during recent decades reflect the growing recognition and formalization of field epidemiology, including establishment of field epidemiology training programs in affiliation with ministries of health and other national-level public health agencies around the world31. Other examples of this trend include the development of field epidemiology courses and tracks within curriculum offerings of schools of public health32; undergraduate programs, and even middle school and high school programs in the United States; the emergence of organizations that promote or link national-level field epidemiology programs; 33and the growth of a body of literature related to the field epidemiology worldwide3435. CDC's own workforce development program in field epidemiology, EIS, has operated continuously since its creation in 1951 and has helped to train more than 4,500 professionals in this discipline3637.

As the discipline of field epidemiology continues to evolve, new developments and trends are shaping its ongoing incorporation within public health practice. Examples of these developments include the following.

• The importance of global epidemiologic capacity building to protect the United States and other populations in an era of expanded travel and population connectivity.
• The potential for parties affected in outbreaks to threaten or actually bring lawsuits and how threatened or actual litigation might affect an ongoing investigation (e.g., complicate or otherwise interfere with data collection or create or increase response bias).
• The importance of ethical public health practice, including the ongoing need to respect privacy and protect confidentiality in the face of the ever-evolving landscape of culture, policy, law, and technology.
• The persistent awareness of and concerns about intentionality as a cause of disease outbreaks, including lower thresholds for considering intentional actions as a primary or contributing determinant for an outbreak and, when criminal or terrorist acts are suspected, the resulting need for public health and law enforcement agencies to coordinate investigations.
• Uses during field investigations of Internet-based and other advanced information technologies for connecting jurisdictions, identifying cases and contacts, conducting surveys or collecting electronically stored health data, and communicating findings and control measures.
• The use of new laboratory methods for multipathogen detection, genetic sequencing, and environmental testing to increase opportunities for detecting and investigating epidemics, emphasizing the need for increased close communication between epidemiologists and laboratory scientists.
• The increasing expectation from the public for government transparency and for timely information about unfolding events, combined with the advent of social media and the 24-hour news cycle for transmitting instant, if not consistently accurate, information, each of which underscores the heightened importance of evidence-based decision-making and enhanced communication skills.

Field epidemiology draws on general epidemiologic principles and methods, and field epidemiologists face questions that are familiar to all epidemiologists regardless of where they work, including questions about how study methods are shaped by logistical constraints and about the amount of information necessary to recommend or take action. Likewise, field epidemiologists are affected by trends that influence the practice of epidemiology in general, such as public concerns about the privacy of health information, the increasing automation of health information, and the growth in use of the Internet. Field epidemiology is unique, however, in compressing and pressurizing these concerns in the context of acute public health emergencies and other events and in thrusting the epidemiologist irretrievably into the midst of the administrative, legal, and ethical domains of policy-making and public health action.

Acknowledgements

Portions of this chapter as incorporated within previous editions of this book were adapted from Goodman RA, Buehler JW, Koplan JP. The epidemiologic field investigation: science and judgment in public health practice. Am J Epidemiol. 1990;132:91–96.