ns and related critical issues. The following provides a brief overview.
I. The Role of Public Health Assessment in Genetics
Public health assessment in genetics relies on scientific approaches to assess the impact of discovered genes on the health of communities. The traditional forms of applied research in public health include surveillance and epidemiology, which are explored in more detail in section II (chapters 6 through 11).
In general, surveillance-the systematic gathering, analysis and dissemination of population data (23)-is needed to determine the population frequency of genetic variants that predispose people to specific diseases, both common and rare; the population frequency of morbidity and mortality associated with such diseases; and the prevalence and effects of environmental factors known to interact with given genotypes in producing disease. Information could be gathered also through broader surveillance of the economic costs of the genetic component of various diseases (e.g., expressed by healthcare costs, hospitalization rates, years of potential life lost and other measures); genetic testing issues (e.g., access to services, quality of tests, usage by providers and potential discrimination); and issues related to interventions (e.g., availability, safety and effectiveness). Examples of existing surveillance and health information systems include the National Health and Nutrition Examination Survey (24), population-based birth defects surveillance systems (25) and cancer surveillance systems (26).
Epidemiology is often viewed as the scientific core of public health. A widely used definition is "the study of the distribution and determinants of health-related states or events in populations, and the application of this study to control health problems" (27). Epidemiologists not only investigate outbreaks of disease in different populations but also conduct studies to determine risk factors for various diseases, identify high-risk subpopulations to which to target prevention and intervention actions, and evaluate the effectiveness of health programs and services in improving the population's health (28).
Over the last two decades, epidemiologic methods and approaches have been increasingly integrated with those of genetics through the discipline of genetic epidemiology, which seeks to identify the role of genetic factors in disease occurrence in populations and families (29). In addition, a new brand of epidemiology has emerged-molecular epidemiology-that seeks to study disease occurrence using biological markers of exposure, susceptibility and effects (30).
Most discoveries for gene variants are based on studies of high-risk families or selected groups. To translate the results of this genetic research into opportunities for treating and preventing disease and promoting health, population-based epidemiologic studies are increasingly needed to quantify the impact of gene variants on the risk of disease, death and disability, and to identify and quantify the impact of modifiable risk factors that interact with gene variants. The results of such studies will help health professionals to better target medical, behavioral and environmental interventions. Epidemiologic studies are also required for clinical validation of new genetic tests, monitoring a population's use of genetic tests, and determining the safety, effectiveness and impact of genetic tests and services in different populations.
To accomplish translation of genetic discoveries into public health practice, epidemiologists must collaborate with practitioners of other disciplines such as clinical genetics, laboratory sciences, behavioral and social sciences, communication sciences, ethics, and law. A combined genetic-epidemiologic approach is essential for better understanding disease etiology and developing molecular diagnostics. Data generated from such collaborations are urgently needed in developing medical and public health policy. For example, issues have been debated regarding population-based genetic testing for breast cancer in relation