Surveillance for Specific Conditions
Surveillance systems are important tools for targeting, monitoring, and evaluating many health risks and interventions. Because managers need a wide variety of information for specific interventions, systems have been developed and tested to meet those needs.
Environmental Public Health Surveillance
Surveillance for environmental public health practice requires the collection, analysis, and dissemination of data on hazards, exposures, and health outcomes (figure 53.4; Thacker and others 1996).
[Figure
53.4]
Health outcomes of relevance include death, disease, injury, and disability. However, relating those outcomes to specific environmental hazards and exposures is critical to environmental public health surveillance. Hazards include toxic chemical agents, physical agents, biomechanical stressors, and biologic agents that are located in air, water, soil, food, and other environmental media. Exposure surveillance is the monitoring of members of the population for the presence of an environmental agent, its metabolites, or its clinically inapparent (for example, subclinical or preclinical) effects.
Four challenges complicate environmental public health surveillance. First, the ability to link specific environmental causes to adverse outcomes is limited by our poor understanding of disease processes, long lead times, inadequate measures of exposure, and multiple potential causes of disease. Second, data collected for other purposes rarely include sufficient information to meet a case definition for a condition caused by an environmental agent. Third, public alarm is often out of proportion to the hazard of concern, and sentiment will often influence public policy disproportionately to scientific information. Fourth, biologic markers will become increasingly critical elements of environmental exposure surveillance.
Obtaining data on exposure, which can include estimates derived from hazard data through sophisticated modeling or direct measurements of individual exposure obtained from use of personal monitors (for example, passive air samplers), is generally impractical in developing countries. Childhood blood lead levels are the only biomonitoring data that are collected routinely in several countries, either in national surveys or from screening programs for children at high risk.
Health outcome surveillance as applied to environmental public health is similar to traditional surveillance efforts. In the United States, the focus is on surveillance for birth defects; developmental disabilities (for example, cerebral palsy, autism, and mental retardation); asthma and other chronic respiratory diseases (for example, bronchitis and emphysema); cancer; and neurological diseases (for example, Parkinson's disease, multiple sclerosis, and Alzheimer's disease) (McGeehin, Qualters, and Niskar 2004). Other nations have different sets of priority conditions for surveillance. Disease registries, vital statistics data, annual health surveys, and administrative data systems (for example, hospital discharge data) are sources that have been used for monitoring health conditions. The challenges mentioned previously have constrained our ability in all nations, regardless of level of development, to establish and maintain effective and comprehensive environmental public health surveillance systems. As we invest in understanding the enlarging threats in the global environment, we must overcome these challenges and establish improved surveillance systems. The health of the global community depends on this investment.
Injury Surveillance
Injuries are a major public health problem and are among the 10 leading causes of death worldwide, killing an estimated 5 million persons each year and causing high rates of disability. People from all economic groups are at risk for injuries, but death rates caused by injury tend to be higher in developing countries (Peden, McGee, and Sharma 2002). Injury surveillance includes monitoring the incidence, causes, and circumstances of fatal and nonfatal injuries. Injuries are classified by the intention of the act into two groups: unintentional injuries and violence-related injuries. WHO (Holder, Peden, and Krug 2001) and the Pan American Health Organization (Concha-Eastman and Villveces 2001) have developed guidelines for establishing injury surveillance systems in developing countries.
If the range of fatal and nonfatal injuries, as well as the risk factors that can lead to injury, are to be fully captured, surveillance systems need to be established in multiple settings. Fatal injuries can be captured by using forensic or death certificate data. A far greater number of injuries are nonfatal and can be tracked through hospital- or primary care-based systems. Systematic information on nonfatal injuries, including prevalence, incidence, and related risk behaviors can also be obtained through ongoing population-based surveys.
Critical points should be addressed when planning an injury surveillance system in a developing country. First, data sources need to be clarified. In some developing countries, routine data on injuries are not always captured in health information systems. It is therefore necessary to consider other sources of data—for example, law enforcement agencies, coroners, or medical examiners. Next, the events and variables in an injury surveillance system should be defined according to the objectives of the system. Criteria such as the intentionality (violence-related injuries versus unintentional injuries); the outcome (fatal injuries versus nonfatal injuries); and the nature of violence-related injuries (physical, sexual, psychological, deprivation, or neglect) should be considered when establishing the system. Finally, case definitions and coding procedures should be defined before implementing the system.
For example, the Nicaraguan Ministry of Health, in collaboration with CDC and the Pan American Health Organization, began developing and implementing an injury surveillance system in 2001 (Clavel-Arcas, Chacon, and Concha-Eastman 2004). The system, based on the medical facility emergency department (ED), collects data on injuries in keeping with the Injury Surveillance Guidelines established by WHO (Holder, Peden, and Krug 2001). Under the system, a reportable case is defined as a patient who died from or was treated for an injury in the ED. Cases include patients with unintentional and violence-related injuries.
ED staff members identify cases and collect data in five hospitals in Nicaragua. Information used to complete the instrument is collected directly from the patients or their representatives. An ED admission clerk collects basic demographic data on the patient's arrival. ED medical staff members (physicians and nurses) collect the remaining information (for example, location, mechanism of injury, nature, severity, and circumstances surrounding the injury) during triage and assessment.
The hospital epidemiologist collects data collection forms daily from the ED, reviews the quality of data, and requests data from the ED staff if the forms are incomplete. The statistician reviews data daily. The country project coordinator also monitors the quality of the data periodically. Using Epi Info 2002 programs developed specifically for this project, the project coordinators analyze trends and identify potential risk factors (Noe and others 2004). The information is used to produce monthly reports for dissemination. Information is reported at both the regional and the country levels.
Injury prevention programs in Nicaragua use surveillance data to assess the need for new policies or programs and to evaluate the effectiveness of existing policies and programs. For example, the municipality of Leon is using the information from the hospital to monitor the increase in suicide attempts among youths abusing pesticides and to evaluate an intersectoral campaign to promote life that includes primary through tertiary prevention strategies.
Surveillance for Biologic Terrorism
Surveillance for biologic terrorism is conducted primarily for outbreak detection and management. Surveillance must support early detection of an incident of biologic terrorism and its characterization in the same manner as for the detection and control of naturally occurring outbreaks of infectious diseases. Early detection of outbreaks can be achieved by the following (Buehler and others 2004):
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timely and complete receipt, review, and investigation of disease case reports, including the prompt recognition and reporting to or consultation with health departments by physicians, health care facilities, and laboratories
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improvement of the ability to recognize patterns indicative of a possible outbreak early in its course (for example, by using analytic tools that improve the predictive value of data at an early stage of an outbreak or by lowering the threshold for investigating possible outbreaks)
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receipt of new types of data (such as purchases of health care products, absences from work or school, symptoms presented to a health care provider, or orders for laboratory tests) that can signify an outbreak earlier in its course.
Environmental detection systems for microbial pathogens and toxins of concern for biologic terrorism might also be categorized as new types of data early in the course of an outbreak, before infection (Meehan and others 2004). The primary surveillance tools for event detection and management are the traditional disease-reporting systems for notifiable diseases discussed elsewhere in this chapter. These core surveillance tools should be robust before new data types can be considered for supplementing public health surveillance.
Syndromic surveillance is an investigational approach by which health department staff members, assisted by automated data acquisition and generation of statistical signals (computerized algorithms), monitor disease indicators continually to detect outbreaks of disease earlier and more completely than might otherwise be possible with traditional reportable disease methods (Buehler and others 2004).
CDC's list of biologic terrorism agents and diseases can be found at http://www.bt.cdc.gov and an updated list of references dealing with syndromic surveillance is at http://www.cdc.gov/epo/dphsi/syndromic/.
Complex Emergency Surveillance
The key elements in planning a disaster surveillance system are establishing objectives, developing case definitions, determining data sources, developing simple data collection instruments, field testing the methods, developing and testing the analysis strategy, developing a dissemination plan for the report or results, and assessing the usefulness of the system. The surveillance needs are different in the preimpact, impact, and postimpact phases (Binder and Sanderson 1987).
The role of surveillance in disaster situations has included the following broad framework of activities:
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predisaster activities (for example, hazard mapping, provision of guidelines, and training for medical and rescue teams)
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continuous monitoring and surveillance for priority health problems in affected populations (for example, in the post-tsunami surveillance in Tamil Nadu, India, a one-page instrument was used for 10 priority health conditions for daily active surveillance in displaced populations at camps)
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prospective surveillance of affected populations focusing on the natural history of exposure and health effects and long-term effects of stress disorders among survivors.
Surveillance in Refugee Populations
Support of relief efforts following national and global disasters has been a relatively new application of epidemiologic practice for the public health professionals. Nevertheless, since the initial CDC involvement with the United Nations in a large-scale relief effort concerning approximately 20 million displaced people affected by the 1967-70 civil war in Nigeria, CDC staff members have participated in several assessments of the health needs, damage, and nutrition in refugee populations resulting from man-made and natural disasters. The more notable and extended actions were conducted in the 1979-82 Khmer Thailand-Cambodia refugee-relief action, followed by long-term public health surveillance of Somalian refugees (1980-83), periodic but comprehensive health and nutritional assessments of Afghan refugees in Pakistan (1980-2002), and growth and nutritional assessments of internally displaced populations—especially children—in the Democratic People's Republic of Korea (1990s) and southern Sudan. Although these relief efforts occurred many years and many thousands of miles apart, they shared several important characteristics:
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Large numbers of people were in fixed camps or on the move searching for food and shelter. These needs were usually addressed by external aid agencies and many times caused local environmental degradation (fuel, temporary housing, water pollution, and so on).
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Refugees, after the initial phase, competed with indigenous populations for scarce jobs, leading to social strife and stress. Refugees were also exploited and suffered violence—additional factors leading to stress and social maladjustment.
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No administrative structure to provide and coordinate assistance of the necessary magnitude existed before the crisis, and thus, it had to be created after the fact.
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Assistance was complicated by the uncertainty associated with military activity, crime, and hostile governments.
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Data that were relatively simple to gather and analyze provided health workers and administrators information needed to plan and monitor assistance and its impact.
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Close collaboration with other local and international relief organizations (such as the United Nations High Commissioner for Refugees, the International Red Cross, the United Nations Children's Fund, WHO, and USAID) was essential to instituting and sustaining a meaningful surveillance system for refugees that led to interventions.
The major goal of these activities is to identify and eliminate preventable causes of morbidity and mortality. Planning requires effective use of existing knowledge about characteristic or predictable demographic patterns, easily applied health indicators, and avoidable errors of omission or commission. As in disasters, the principles of surveillance (data collection, data analysis, response to data, and assessment of response) and other public health techniques should be an integral part of relief efforts. Retrospective evaluation of these efforts has also proved useful (CDC 1983).
Chronic Disease Surveillance Systems
Development and evaluation of policies for health improvement require a reliable assessment of the burden of disease and injury, an inventory of the disposition of resources for health, assessment of the policy environment, and information on the cost effectiveness of interventions and strategies. In all these areas, consideration of noncommunicable (mostly chronic) conditions becomes critical. In 1999, noncommunicable diseases were estimated to cause approximately 60 percent of the deaths in the world and 43 percent of the global burden of disease (WHO 2000a). WHO forecasts that by 2020 the burden of disease from noncommunicable diseases for developing and newly industrialized countries will have increased more than 60 percent (Murray and Lopez 1996).
Some developing countries have found it difficult to acquire and analyze accurate mortality statistics regularly, let alone morbidity and quality-of-life information. Ensuring development, implementation, and widespread use of noncommunicable disease data for better decisions on resource allocation is critical to improving the quality of lives and promoting a more equitable future for health within and between countries.
Hypertension, elevated blood cholesterol, tobacco use, excessive alcohol consumption, obesity, and the multiple diseases linked to these risk factors are a global public health problem. In one study, smoking, high blood pressure, and high cholesterol alone explained approximately two-thirds to three-fourths of heart attacks and strokes (Vartiainen and others 1995). Until recently, surveillance for risk factors was an activity commonly associated with developed countries (Holtzman 2003). However, recently WHO has increased attention to noncommunicable disease surveillance by developing tools and working to achieve data comparability between countries (WHO 2003c). Data on key health behaviors, obesity, hypertension, lipids, and diabetes are collected inconsistently in developing countries, especially in Africa. Data on tobacco use are available through the Global Youth Tobacco Survey (http://www.cdc.gov/tobacco/global).
Incidence data (the number and proportion of new cases in a population) are limited in developing countries. However, India's National Cancer Registry program may serve as a notable exception (http://icmr.nic.in/ncrp/cancer_regoverview.htm). In 1981, the Indian Council of Medical Research, recognizing that there was a lack of information on follow-up of cancer patients to assess quality of care, instituted a cancer registry network. The network provides data on the magnitude and patterns of cancer in eight areas of India to enable studies of the histologic features correlating with prognosis and association studies (for example, whether a history of vasectomy is associated with cancer of the prostate). Another important example relates to the widespread use of folic acid in China and the resultant reduction in incidence of birth defects (Kelly and others 1996; Wald 2004).
Surveillance data have been critical in establishing the importance of obesity as a public health priority in the United States. Data for individual states provided by CDC's BRFSS have enabled individual health departments to document their obesity epidemic (Sturm 2003). These data provide a measure of the effectiveness of interventions to meet the control objectives. The BRFSS is a practical tool for developing and middle-income countries, as Jordan demonstrated when it implemented a BRFSS in 2002; the first survey documented substantial levels of obesity, especially among women, combined with low levels of physical activity (CDC 2003b).
