PUBLIC HEALTH SURVEILLANCE

SURVEILLANCE AND MONITORING zHealth Surveillance -- the collection, analysis and interpretation of data on individuals or groups to detect the occurrence of certain events and their putative causes for (1) the purpose of prevention or control of certain diseases and other health conditions, (2) formulation of interventions, and (3) evaluation of the impact of programs zGenerally, surveillance requires three functions in this sequence: (1) data collection, (2) analysis and interpretations, and (3) decision making

zSurveillance may be performed using data from a variety of sources: zMortality Data derived from death certificates and population censuses analyze by census tract characteristics such as geographic regions and socioeconomic status of the population zMorbidity and Disability Data derived from regularly available sources such as hospitals, industry and schools. Morbidity and disability data may also be obtained via surveys of representative samples of populations -- e.g., National Health Interview Survey, BRFSS

zSpecially Designed Data Sources such as cancer registries, which combine mortality and morbidity and serve many surveillance uses. For example, time trends for site-specific cancers, cancer control measures, new treatments, and the emergence of rare cancers may be identified and evaluated using cancer registries

zBiologic Characteristics such as population growth, blood pressures, and nutritional status may also be the subject of surveillance -- e.g., growth of school children made once a year and supplemented by additional information from students and parents on nutritional status, respiratory functions, etc. Allows comparison of such indicators as height and weight of equivalent age groups in successive calendar years as well as the comparison of annual growth rates of various age cohorts

PURPOSES OF PUBLIC HEALTH SURVEILLANCE zDescribing trends and the natural (secular) history of health problems zDetecting epidemics zProviding details about patterns of disease zMonitoring changes in disease agents through laboratory testing zPlanning and setting health program priorities zEvaluating the effects of prevention and control measures zDetecting critical changes in health practices

zEvaluating hypotheses about the cause of health problems zDetecting rate but important cases of diseases, such as botulism

TYPES OF SURVEILLANCE zFour general categories of public health surveillance zPassive Surveillance yThe most commonly practiced disease surveillance at state and local health departments -- generally used standardized reporting cards or forms that are distributed in batches to hospitals, clinics, laboratories and other health care settings yPassive surveillance usually targets physicians, laboratories, and infection control officers yReferred to as passive because no action is taken unless completed reports are received by the public health agency and further public health action is deemed desirable yCompleteness of reporting is usually lowest for passive systems, but they tend to be the least expensive to maintain

TYPES OF SURVEILLANCE (cont’d.) zActive Surveillance yActive surveillance involves an ongoing search for cases yThis may involve regular contacts with key reporting sources, such as telephone calls to physicians or laboratories, or a frequent review of data that may include cases of a specific condition, such as a review of laboratory logs for certain bacterial isolates or a review of admissions to burn units to identify severely burned individual yActive surveillance systems may have high levels of completeness but are usually much more expensive to maintain; some question the cost-effectiveness of active surveillance

TYPES OF SURVEILLANCE (cont’d.) zSentinel Surveillance ySentinel surveillance involves the use of a sample of providers -- most generally, a sample of physicians or emergency rooms -- to identify trends in diseases that occur at relatively high frequencies yE.g., sentinel surveillance systems, such as those for influenza, provide timely information about trends in influenza-like illness activitiy, and are useful for obtaining information about strains that may be circulating in a community -- assuming that there is a laboratory-based component to the surveillance

TYPES OF SURVEILLANCE (cont’d.) zSpecial Surveillance System ySpecial surveillance systems have been found useful for certain types of surveillance activities yThe Behavior Risk Factor Surveillance System (BRFSS) involves administering a questionnaire to a random sample of individuals on a ongoing basis to identify trends in behavior that affect health risk -- e.g., monitoring the impact of such activities as breast cancer screening with mammography, cervical cancer with pap smears, use of smoke alarms in houses, as well as other health-related behaviors and practices yMocrobiologic surveys have been useful in determining the antibioltic resistance among persons with invasive pneumococcal infections

THE BEHAVIORAL RISK FACTOR SURVILLANCE SYSTEM (BRFSS) zIn 1981, the CDC began helping states and communities to survey adults, 19 years and older, by telephone about their health behaviors zIn 1984, the CDC initiated the BRFSS to enable states to collect state-specific behavioral risk factor data zData are used to estimate the prevalence of behaviors related to the leading causes of death and disability, and are available by such control variables as age, race, sex, income, and education

THE BEHAVIORAL RISK FACTOR SURVILLANCE SYSTEM (BRFSS) zBy 1994, all 50 states and D.C. were participating in the BRFSS -- a telephone survey using random-digit dialing and a probability sample of U.S. householdsl zThe BRFSS survey instrument consists of: yCore questions asked in all states -- dealing primarily with recent or current behaviors that are risk factors for disease or injury and with quality of life indicators yStandard modules -- sets of questions developed by the CDC on specific topics suggested by states -- each state decides every year which, if any, standard modules they will include yState-specific questions -- included only in a particular state’s survey coverage