24 Public Health Surveillance

Dimkhoihoi Baite and Sanjenbam Yaiphaba Meitei

epgp books

 

Contents:

 

1.0 Introduction

 

2.0 Model of the cycle of Surveillance

 

3.0 Importance of Surveillance

 

4.0 Types of Surveillance

 

4.1 Active Surveillance

 

4.2 Passive Surveillance

 

4.3 Sentinel Surveillance

 

5.0 Purposes of Surveillance

 

6.0 Uses of Public Health Surveillance System

 

7.0 Summary

 

 

Learning Objectives:

  •  after reading this module, you will be able to:
  •  define the meaning of public health surveillance;
  •  explain the main uses of surveillance data and information in public health practice;
  •  identify and discuss the steps in the surveillance cycle;
  •  describe the different types of surveillance; and
  •  what are the uses of public health surveillance system?

 

1.0 Introduction

 

Public health surveillance is the ongoing systematic collection, analysis, and interpretation of health related data essential to the planning, implementation and evaluation of public health practice, closely integrated with the timely dissemination of these data to those responsible for preventing and controlling disease and injury (Thacker and Berkelman 1988). Public health surveillance is a tool to estimate the health status and behaviour of the populations served mostly by Government health agency. Because surveillance can directly measure what is going on in the population, it is useful both for measuring the need for interventions and for directly measuring the effects of interventions. The purpose of surveillance is to empower decision makers to lead and manage more effectively by providing timely, useful evidence. Apart from the government agencies, surveillance has also become an integral part of health research.

 

The concept of surveillance dates from as far back as John Graunt in the 17th century and William Farr in the 19th century. Graunt was the first to quantify patterns of birth, death and disease. Farr, who is known as the “father of modern vital statistics and surveillance”, systematically collected and analyzed Britain’s vital statistics, particularly occupational mortality, for the General Register Office. From these beginnings, surveillance has continued to evolve into a major mechanism by which public health practitioners monitor the health of the community. The importance of surveillance in protecting individual nations and the global community been often highlighted in the case epidemics. Currently different countries have expanded nation’s own surveillance. For example, in 2005, China rapidly began to expand its surveillance and response capacity through its Field Epidemiology Training Program (FETP); Brazil and Argentina chose to use World Bank loans to develop surveillance capacity; and the U.S. Agency for International Development (USAID) redesigned its surveillance strategy to focus on the use of data to improve public health interventions (USAID 2005). Moreover, WHO formulated the guidelines to implement International Health Regulations, for which the member states to have key persons and core capacities in surveillance (http://www.who.int/csr/ihr/howtheywork/faq/en/#draft).

 

Surveillance information is really “information for action” – in order to be useful and effective, it needs to be transmitted to those who can take action to control or prevent further harm to individuals or communities. Given the intersectoral nature of public health, this may include not only those working within the health sector, but may also other sectors including both government and non-government agencies including NGOs, depending on the circumstances.

 

 

2.0 Model of the Cycle of Surveillance

 

Health surveillance is an ongoing cycle of public health actions that involve both health service providers and agencies. In general, the cycle begins when a case of a disease or other health event occurs and is reported by a health

 

practitioner to a public health agency. The cycle is not completed until information has been collected, integrated, analysed, interpreted, surveillance products produced and, most importantly, disseminated to “those who need to know”, including the health practitioner who first reported the event, health agencies and the public (https://cursos.campusvirtualsp.org/mod/tab/view.php?id=23160).

The surveillance cycle consists of the following components:

 

Collection of data Integration

 

Analysis and interpretation

 

Development of surveillance products Dissemination

 

Evaluation

 

Collection of Data: Data collection is one of the important components for the surveillance. Prior to data collection, data framework should be defined for which the surveillance is to be recorded. The data framework is usually defined in terms of indicators. An indicator is a measurable factor that allows decision makers to estimate objectively the size of a health problem and monitor the processes, the products, or the effects of an intervention on the population (Nsubuga et al., 2016). Choosing the best sources and methods for gathering the data are needed in this stage. This may need to balance competing needs for timeliness, simplicity, and completeness. Proper designing and selection of tools is needed to get required data. These data may be collected for a variety of purposes – for surveillance to administer health services, research purposes that actually have an impact on health, statutory reasons, etc. Key data collection can be of health survey approach wherein risk factors to any health issue be screened in a population. It can be also of administrative data which is compiled from both service provider based systems (e.g. hospital or laboratory records) and population based systems (e.g. vital records) and the concerned administrative department. For communicable disease cases, it will be mandatory reports. Further, it can be again of voluntary reports or Studies of special groups according to the special attention of the data collection (Choi, 2006). Information collected on novel diseases include characteristics such as the type of pathogen involved, symptoms caused, the infected population, and the morbidity and mortality rates.

 

Integration: Data collected from a number of sources provide a more comprehensive picture of the trend of the concerned topic for which surveillance is made. Different information collected from different sources at different time period of the surveillance need to be assembled or compiled for systematic analysis of the data.

 

Analysis and Interpretation: The analysis and interpretation stage includes expert analysis of the data that have been collected to determine the occurrence of a health concern and the characteristics and behaviours of people with a health concern as well as changes over time. Surveillance data initially should be analyzed in terms of time, place, and person (Brachman, 1982), by looking at time trends and geographic distribution and comparing age, sex, and population groups (Chambers et. al., 2006). Special analytical tools such as cluster and time series analysis or computer mapping techniques, are being used for analysis in present days. Data analysis is followed by interpretation. Interpretation involves consideration of whether the apparent increases in disease occurrence, within a specific population at a particular time and place, represent true increases. Possibilities for variation include an increase in population size, improvement in diagnostic procedures, enhanced reporting, duplicate reporting, and other changes in the system. Understanding of the sources of possible study biases can help interpretation of results. In many instances it may be difficult to decide if the change detected is real or artificial, but this question must be answered before action can be contemplated. Data cannot stand alone in a surveillance system – raw data, without context and interpretation, can be analyzed to produce very different conclusions, and can also be applied inappropriately to populations to which they do not refer. The process of analyzing and interpreting the data is an integral part of a surveillance system: the appropriate analyses must be standardized. The analysis is always guided by the important questions or hypotheses in the topic area and the analysis methods must be provided in a manner that can be readily understood by the intended audience. The analysis first considers the three variables of person, place and time, and, in general, current data is compared to baseline or expected data values.

 

Development of Surveillance products: The information generated in the surveillance needs to be transmitted for action to take up remedial measures to control or prevent from further damage. The process of analyzing and interpreting surveillance data results in the development of a wide variety of products, which aims at transforming the information into actions. These surveillance products can take various forms, depending on the target population as in the form of health alerts or advisories, press releases, and annual reports, etc.

 

Dissemination and Evaluation: The final stage in the public health surveillance process is the timely communication of information to users or the public and it is important for follow-up action. Surveillance users include public health practitioners, health planners, epidemiologists, researchers, and policy-makers as well as members of the public and the media. Public health decision making depends on three types of knowledge: surveillance, scientific research, and lay experience. Surveillance knowledge includes statistics that measure health outcomes, health care performance, and other determinants of health. Public health practitioners and researchers need to understand and effectively communicate these three complementary types of knowledge. Dissemination of surveillance information is one of the most important aspects of the surveillance cycle as regular and timely data dissemination allows effective control and prevention. The reports disseminated needs to be evaluated thoroughly by concerned authority especially policy makers to control the health problems.

 

4.0 Types of Surveillance

 

Type of surveillance may differ from one disease to another depending on the attributes of the disease and the objectives of the immunization programme. Broadly surveillance can be of three types:

 

4.1 Active Surveillance: Active surveillance involves visiting health facilities, talking to health-care providers and reviewing medical records to identify suspected cases of disease under surveillance. Designated active surveillance staff regularly visit health facilities in person to search for suspected cases among persons who might have attended the facility. In fact, it involves physical review of medical records and registers, interviews with health care workers and visits to relevant outpatient clinics and hospital wards. When a case is found, the active surveillance staffs investigate it, document clinical and epidemiological data, arrange to send appropriate laboratory specimens and report the information rapidly, according to national policy. This method is usually used when a disease is targeted for eradication or elimination, when every possible case must be found and investigated. It is also used for outbreak investigations. This type of surveillance requires substantially more time and resources and is therefore less commonly used in emergencies, but it is often more complete than other type of surveillance. It is frequently used if an outbreak has begun or is suspected to keep close track of the number of cases.

 

4.2 Passive Surveillance: Passive Surveillance often gathers disease data from all potential reporting health care workers. Regular reporting of disease data by all institutions that see patients (or test specimens) and are part of a reporting network is called passive surveillance. Unlike active surveillance, there is no active search for cases in this type of surveillance. It relies on the reports or data generated by the concerned health agencies. It works mainly on the cooperation of health-care providers like laboratories, hospitals, health facilities and private practitioners. Once the data have been received, they must be compiled and then analyzed to monitor disease patterns and identify possible outbreaks. It is the most common method used to detect vaccine-preventable diseases as it involves the regular collection and reporting of surveillance data. Moreover, it is less expensive than other surveillance strategies and covers wide areas (whole countries or provinces); however, because it relies on an extensive network of health workers, it can be difficult to ensure completeness and timeliness of data.

 

4.3 Sentinel Surveillance: A sentinel surveillance system is used when high-quality data are needed about a particular disease that cannot be obtained through a passive system. Selected reporting units, with a high probability of seeing cases of the disease in question, good laboratory facilities and experienced well-qualified staff, identify and notify on certain diseases. The difference from passive surveillance is that it involves only a limited network of carefully selected reporting sites rather than numerous sites of passive surveillance. Data collected in a well-designed sentinel system can be used to signal trends, identify outbreaks and monitor the burden of disease in a community, providing a rapid, economical alternative to other surveillance methods. However, it may not be as effective for detecting rare diseases or diseases that occur outside the catchment areas of the sentinel sites as it is conducted only in selected locations.

 

There are certain criteria to be taken care in selecting a sentinel health facility (usually a general or infectious disease hospital):

 

It should be willing to participate.

 

It should serve a relatively large population that has easy access to it.

 

It should have sufficient medical staffs, specialized in diagnose, treat and report cases of the disease under surveillance.

 

It should have high-quality diagnostic laboratory.

 

 

Attributes of Surveillance

 

In general, public health surveillance system has the following attributes (Romaguera et al. 2000) such as,

 

a) Simplicity: Easy to operate, elegance of design and limitation of size.

b) Flexibility: Ability to adapt to changing needs.

c) Acceptability: Willingness to participate in the system.

d) Sensitivity: Ability to detect epidemics or health problems.

e) Positive predictive value: Proportion of case identified.

f) Representativeness: Accurate description of the occurrence of a health event over time or its distribution.

g) Timeliness: Ability to take appropriate public health action.

h) Cost: Resources used to operate the system.

 

5.0 Purposes and Uses of Surveillance: Public health surveillance provides and interprets data to facilitate the prevention and control of disease. To achieve this purpose, surveillance for a disease or other health problem should have clear objectives. It includes the following objectives

  • Assess health status of a population,
  • Prioritize public health,
  • Assess program effectiveness,
  • Stimulate research.

Surveillance systems generate data that help public health officials understand existing and emerging infectious and non-infectious diseases. Without a proper understanding of the etiology, distribution, and mechanism of infection, it will be difficult to enhance the health issue. Continued data collection is needed to monitor new diseases that threaten global health security (like the Ebola virus) and the changes in distribution and virulence of well-known diseases (like the Influenza virus). Without surveillance, public health officials would be unable to dissect the problems thoroughly. Moreover, Public Health Surveillance system has also been used to determine geographic distribution of illness, to understand the natural history of a disease, to detect outbreaks or epidemics, to generate hypothesis about etiology of a disease, and to facilitate epidemiologic and laboratory research. Finally, the information generated in the surveillance will be of significance in health planning and policy makers, which ultimately can evaluate the existing system and look for better and alternative measures.

 

Public Heath Surveillance and Research

 

It is already mentioned earlier that surveillance facilitate epidemiologic and laboratory research. Health research has been the important arena of research since long time. Understanding the human health problems is being one of the important concerns of health scientists including anthropologists. Research findings from both governmental and non-governmental agencies being the important sources of data of the surveillance. At the same time, official reports published as surveillance products are also being analyzed deeper to probe out the factors associated with disease etiology. Research promotes the analytical skill to understand the human health problems more thoroughly. In the era of complex disorders, health research becomes an important arena for epidemiologists. Redefining the complex nature of such disorders has been the target for epidemiologist. Moreover the concept of translational research in the health issues, wherein the research findings being translated to the public, adopts the dissemination nature of public health surveillance. Even it can be said health research is a part of health surveillance.

 

 

Summary

 

  •  Public health surveillance is the ongoing systematic collection, analysis, and interpretation of health related data essential to the planning, implementation and evaluation of public health practice.
  •  The purpose of surveillance is to empower decision makers to lead and manage more effectively by providing timely, useful evidence.
  •  The surveillance cycle consists of five components, they are: Collection of data, Integration, Analysis and interpretation, Development of Surveillance products, Dissemination and Evaluation.
  •  Proper designing and selection of data collection tools is needed to get accurate information.
  •  Different information collected from different sources at different time period of the surveillance need to be assembled or compiled for systematic analysis of the data.
  •  Special analytical tools such as cluster and time series analysis or computer mapping techniques, are being used for analysis in the present days.
  •  The analysis is always guided by the important questions or hypotheses in the topic area and the analysis methods must be provided in a manner that can be readily understood by the intended audience.
  •  The process of analysing and interpreting surveillance data results in the development of a wide variety of products, which aims at transforming the information into actions.
  •  Public health decision making depends on three types of knowledge: surveillance, scientific research, and lay experience.
  •  Dissemination of surveillance information is one of the most important aspects of the surveillance cycle as regular and timely data dissemination allows effective control and prevention.
  •  The different types of Surveillance are: Active, Passive and Sentinel.
  •  Type of surveillance may differ from one disease to another depending on the attributes of the disease and the objectives of the immunization programme.
  • Active surveillance involves visiting health facilities, talking to health-care providers and reviewing medical records to identify suspected cases of disease under surveillance.
  •  Passive Surveillance often gathers disease data from all potential reporting health care units.
  •  A sentinel surveillance system is used when high-quality data are needed about a particular disease that cannot be obtained through a passive system.
  •  Attributes of Surveillance includes simplicity, flexibility, acceptability, willingness, sensitivity, positive predictive value, representativeness, timeliness and cost.
  •  Public health surveillance provides and interprets data to facilitate the prevention and control of disease.
  •  The information generated in the surveillance will be of significant in health planning and policy makers, which ultimately can evaluate the existing system and look for better and alternative measures.
  •  The concept of translational research in the health issues, wherein the research findings being translated to the public, adopts the dissemination nature of public health surveillance.
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