Public Health Surveillance in the United States: Evolution and Challenges*

Stephen B. Thacker, MD1, Judith R. Qualters, PhD2, Lisa M. Lee, PhD1

1 Office of Surveillance, Epidemiology and Laboratory Services, CDC

2 National Center for Environmental Health, CDC

Corresponding author: Stephen B. Thacker, MD, USPHS, Office of Surveillance, Epidemiology and Laboratory Services, CDC, 2400 Century Center, MS E-94, Atlanta, Georgia, 30329; Telephone: 404.498.6010; Fax: 404.498.6365; E-mail: sthacker@cdc.gov.

"In public health, we can't do anything without surveillance.
That's where public health begins."
— David Satcher, MD, PhD, U.S. Surgeon General, 1998–2002

In its landmark 1988 report, a committee of the Institute of Medicine highlighted assessment as one of the three core functions of public health along with policy development and assurance (1). The committee recommended that every public health agency regularly and systematically collect, assemble, analyze, and make available information on the health of the community, including statistics on health status, community health needs, and epidemiologic and other studies of health problems. Public health surveillance, often called the cornerstone of public health practice, is an essential element of the assessment function.

Public health surveillance is the systematic, ongoing collection, management, analysis, and interpretation of data followed by the dissemination of these data to public health programs to stimulate public health action (2). The best recognized use of public health surveillance data is the detection of epidemics and other health problems in a community, but there are many other uses that are critical to public health practice. These data are used to estimate the scope and magnitude of a problem, including the geographic and demographic distribution of health events that will facilitate public health planning. Surveillance data also can be used to detect changes in health practices, monitor changes in infectious and environmental agents, evaluate control measures, and describe the natural history of a health event in a community that will generate hypotheses and stimulate applied research (3). In short, public health surveillance is the foundation for decision making in public health and empowers decision makers to lead and manage more effectively by providing timely, useful evidence (4).

In the United States, public health surveillance has focused historically on infectious diseases. Basic elements of surveillance were found in Rhode Island in 1741, when the colony passed an act requiring tavern keepers to report contagious diseases among their patrons. Two years later, the colony passed a broader law requiring the reporting of smallpox, yellow fever, and cholera (5). Lemuel Shattuck's 1850 report of the Massachusetts Sanitary Commission was a landmark publication that related death, infant and maternal mortality, and communicable diseases to living conditions. Shattuck recommended a decennial census; standardization of nomenclature of causes of disease and death; and a collection of health data by age, sex, occupation, socioeconomic level, and locality. He applied these concepts to program activities in the areas of vaccination, school health, smoking, and alcohol abuse and is credited with introducing related concepts into the teaching of preventive medicine (5).

Activities associated with disease at the national level began in the United States in 1850 when mortality statistics based on death registration and the decennial census were first published by the federal government for the entire country. Systematic reporting of disease in the United States began in 1874, when the Massachusetts State Board of Health instituted a voluntary plan for physicians to provide weekly reports on prevalent diseases, using a standard postcard-reporting format. In 1878, Congress authorized the forerunner of the U.S. Public Health Service (PHS) to collect morbidity data for use in quarantine measures against such pestilential diseases as cholera, smallpox, plague, and yellow fever (5).

In 1893, Michigan became the first jurisdiction to require the reporting of specific infectious diseases. Also in 1893, a law was enacted to provide for collecting information each week from state and municipal authorities throughout the United States. By 1901, all state and municipal laws required notification (i.e., reporting) to local authorities of selected communicable diseases that included smallpox, tuberculosis, and cholera. In 1914, PHS personnel were appointed as collaborating epidemiologists to serve in state health departments and to telegraph weekly disease reports to PHS (5).

In 1925, following markedly increased reporting associated with the severe poliomyelitis epidemic in 1916 and the influenza pandemic in 1918–1919, all states began participating in national morbidity reporting. Mortality data related to pneumonia and influenza were reported from 50 cities beginning in 1918 in the throes of a devastating pandemic, and that system has expanded and continues to the present to include 122 cities in 2012. A national health survey of U.S. citizens was conducted first in 1935. After a 1948 PHS study led to the revision of morbidity reporting procedures, the National Office of Vital Statistics assumed the responsibility for this activity. In 1949, weekly statistics that had appeared for several years in Public Health Reports began being published by the National Office of Vital Statistics. In 1952, mortality data were added to the publication that was the forerunner of MMWR (5).

Alexander Langmuir, the first chief epidemiologist at CDC, is recognized as the founder of public health surveillance, as it is known today, and his seminal 1963 publication describes the application of surveillance principles to populations rather than individual patients with a communicable disease (6). Langmuir worked with like-minded colleagues at the World Health Organization (WHO) to organize the 1968 World Health Assembly session on National and Global Surveillance of Communicable Diseases, and epidemiologic surveillance became a global practice (7).

In 1951, Langmuir established the Epidemic Intelligence Service (EIS), which provided a unique approach to training men and women in applied epidemiology (8). The program not only provided the epidemiologists for the 1955 polio investigation but has trained approximately 3,000 epidemiologists during the past six decades in the principles and practice of public health surveillance. It is now emulated as Field Epidemiology Training Programs in approximately 30 countries around the world (9,10). Langmuir also encouraged the organization of the state and territorial epidemiologists in 1952, and the Council of State and Territorial Epidemiologists now speaks effectively for the practice of applied epidemiology in the states. Other legacies of the Langmuir influence include surveillance programs in abortion, birth defects, and other crucial areas of reproductive health.

However, a single event in 1955 first put Langmuir, CDC, and public health surveillance on the map (11). The inactivated polio vaccine had become available in the spring of that year. However, soon after that national vaccine program began, cases of polio were linked to the vaccine, and the U.S. Surgeon General shut down the program. In a matter of days, Langmuir and his team of EIS officers set up a national surveillance system with daily reports from all the states and territories that were sent to the Surgeon General. Officers were sent to the field and within weeks, the source of the problem was detected and identified at a single manufacturer. As a result, the Surgeon General was able to reassure the public and restart the vaccination program within months.

In the early 1980s, a concerted effort at CDC focused on the practice of surveillance, and in 1986, an internal report included the following revised definition of epidemiologic surveillance: The ongoing, systematic collection, analysis, and interpretation of health data essential to the planning, implementation, and evaluation of public health practice, closely integrated with the timely dissemination of these data to those who need to know (12). The final link in the surveillance chain is the application of the data to prevention and control and includes a functional capacity for data collection, analysis, and dissemination linked to public health programs (12).

The 1986 internal report was directed at CDC but also included information and recommendations (e.g., a systematic approach for evaluating surveillance systems). A subsequent paper described the confusion engendered by use of the qualifying word "epidemiologic" to describe surveillance and argued for the use of the broader term "public health" instead (13). That paper also carefully defined the boundaries of public health surveillance, especially in terms of research and practice.

Current and Future Challenges

Given the proliferation of data systems, developments in preparedness and emergency response, rapid maturation and dissemination of the information sciences, and new tools and technologies, the time has come to reassess what is meant by public health surveillance. To begin this process, the planning committee for this consultation solicited the opinions of CDC/ATSDR scientists and managers on the state of surveillance at the agency. Division directors, members of the Surveillance Science Advisory Group (SurvSAG), and scientists on the science distribution list were invited to share their opinions. A web-based surveillance survey was established in the spring of 2009. A total of 434 persons responded to the survey. Approximately 60% of respondents agreed that the general state of surveillance at CDC is strong; only 16% disagreed. The question is where does the agency go from this point?

Only one third of CDC survey respondents agreed that the agency analyzes and disseminates surveillance data in a timely fashion, and only one in five reported that CDC surveillance systems are flexible and readily able to adopt new methods in a rapidly changing environment. In short, the agency and its scientists and managers must adapt and transform its surveillance systems to meet the public health practice needs of today and tomorrow.

"For surveillance systems to be useful, they must adapt to
the changing environment in which they operate and
accommodate emerging public health requirements that
were not conceived previously."
— Joseph S. Lombardo, MS,
Johns Hopkins University Applied Physics Laboratory, and David L. Buckeridge, MD, PhD, McGill University (14)

To advance public health surveillance in the 21st century, at least six major concerns must be addressed by the public health community: a common lexicon; global surveillance needs; informatics, including information technology; a skilled workforce; data access and use; and data management, storage and analysis.

Lexicon

The first concern is basic and deals with the lexicon that practitioners use, definitions, and the conceptual framework that is understood by those in public health and elsewhere who need to know. Terms used to modify surveillance are numerous, starting decades ago with "disease," "epidemiologic," "active," "passive," and "sentinel" and evolving to "integrated" and "syndromic" in recent years. Data-source terms (e.g., office-based, laboratory-based, and hospital-based) are used to clarify but sometimes only obfuscate. To complicate the lexicon further, every program adds a surveillance system modifier (e.g., chronic disease, environmental health, unintentional injury, and occupational) and surveillance systems also exist for behaviors or events (e.g., disasters or political conventions). Each new system will be designed with a different meaning and specialized framework. Most recently, the term "biosurveillance" was mandated by a Presidential Directive (Homeland Security Presidential Directive 21 [http://www.hsdl.org/?view&did=580002]), which was defined specifically to relate to such acute events as a terrorist threat or an influenza epidemic. These differences neither lead to clarity of purpose nor facilitate understanding.

A conceptual framework for health knowledge is a step toward increased understanding (Figure 1). Knowledge of the health of and health risks in a community or population depends on certain inputs in addition to public health surveillance, including research studies that produce generalizable knowledge, health surveys, registries of vital events (e.g., births and deaths), medical and laboratory information systems, environmental monitoring systems, censuses, and other data resources. However, a conceptual framework for public health surveillance examines many of the same data systems (Figure 2).

Global Surveillance Needs

CDC is an agency with global reach, and the agency and the world must collaborate for global public health surveillance. WHO has developed a global framework for infectious disease surveillance, which includes formal collaborators (e.g., national public health authorities and WHO collaborating centers and laboratories) and informal collaborators (e.g., nongovernmental organizations, including foundations) (Figure 3) (14). According to the planning committee survey, CDC scientists and managers agree to a limited degree (40%) that the agency maintains international partnerships to address global surveillance needs; however, one in four respondents did not know or had no opinion on this question. Clearly, through expanding global efforts in such vertical programs as global immunization, the acquired immunodeficiency syndrome programs, and the Field Epidemiology Training Programs, a strong effort should be directed towards public health surveillance.

Information Science and Technology

The roles of surveillance in information sciences and emerging technologies is possibly the most pressing issue that confronts the agency and its partners. At the same time, virtually everyone in public health acknowledges that the progress in informatics, including information technology, has paved the way for exciting opportunities to practice public health surveillance more efficiently and effectively. However, only 22% of respondents to the CDC survey agreed that CDC surveillance systems work well in today's world of information technology, and 60% of respondents agreed that the agency should provide and support a common standard for the informatics framework applicable to all surveillance systems across the agency. Data quality can be improved and information made accessible in a more timely manner, especially through use of integrated electronic health records.

Through improved tools and better strategies, the opportunity exists to link to important data not available traditionally in public health. For CDC and its partners to take advantage of these opportunities, development and use of standards should be improved to facilitate data exchange. This will depend on more effective policies to enable partnering with state and local health departments as well as other federal agencies engaging in public health surveillance (e.g., the U.S. Departments of Homeland Security and Defense and the Environmental Protection Agency [http://www.hsdl.org/?view&did=580002]) and our global partners both governmental and private. This will require substantial time, resources, effort, and commitment. Approximately 70% of CDC scientists and managers agreed that CDC leadership values the work and scientific contribution of surveillance activities, and in 2009, the CDC Director made surveillance a visible priority for this agency. Meanwhile, only 18% of respondents agreed that the agency adequately funds surveillance activities and that increased resources to rebuild partnerships to address local, state, and global surveillance were needed both centrally (51%) and in individual programs (69%). However, to be useful, technology must have a purpose; user requirements must have a higher priority than solutions that are technologically exciting (15).

Skilled Workforce

Two thirds of the CDC survey respondents agreed that CDC has surveillance expertise across subject matters throughout the agency; however, only 38% agreed that the agency offers training that promotes high-quality surveillance methods. Approximately 70% of respondents agreed that CDC should implement a broad initiative to train all agency staff about skills needed for effective public health surveillance in the 21st century. An even greater existing and future need exists for workforce development in state and local health departments and internationally (16,17). Despite the increasing efficiencies that automation might bring to surveillance, even in the most sophisticated systems, human input will remain large and consequential (Figure 4).

Data Access and Use

A fifth major issue in advancing public health surveillance relates to accessing and using data. A limited number of respondents to CDC's survey (20%) agreed that CDC provides timely access to surveillance data internal to the agency through centralized data bases, and a slightly higher percentage (25%) agreed that the agency provides timely access to public use datasets from surveillance activities. In contrast, a substantial percentage (77%) agreed that CDC should apply consistent standards across the agency for timely dissemination of surveillance data. The opportunities are great. The future system is likely to consolidate information in health information exchanges that allow providers and institutions to share patient data among themselves and with public health agencies without having to turn over the data to the participating institutions. Nationally, an electronic health grid could include consumers, providers, and public health agencies at all levels participating in such data sharing for public health surveillance (Figure 5). In this grid, data can be shared without violating confidentiality and the "owner" remains the responsible steward for ensuring this and other factors (e.g., quality and discoverability). This "shared" model facilitates improved public health by providing access and a relation among complex data sets/systems.

Data Management, Storage and Analysis

The last concern relates to analytical challenges, and the most urgent of these challenges relates to data base management. With the increasing availability of clinical, insurer, social, and environmental data sets, the immediate challenge is to organize the data into a format that is accessible and useful for epidemiologists, statisticians, and others who might be able to use these data for public health surveillance. Until these data are available in a useable format, interpretation by subject matter experts is impossible and the data will not be useful. Only 28% of survey respondents agreed that the agency maintains rigorous standards for the collection, maintenance, and analysis of data for CDC/ATSDR and its partners. Clearly, there remains much to do.

Conclusion

In summary, the challenge remains to take this opportunity to build on the existing organizational resources and common interests to strengthen public health surveillance. This consultation offers a tremendous opportunity to inform and shape the direction of the new organizational unit to be developed under the new Deputy Director for Surveillance, Epidemiology, and Laboratory Services. This is also an opportunity to build relationships with other surveillance professionals at CDC/ATSDR through shared knowledge and experience and has the potential to build collaborations that can leverage resources and expertise to enhance the practice of public health surveillance at the agency and among our partners, domestic and international.

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