Epidemiological Surveillance (ES)

1. Definition:

Epidemiological surveillance (ES) is the systematic and ongoing collection, analysis, interpretation, and dissemination of health information. This activity plays a crucial role in monitoring the health status of a population, identifying health risks and outbreaks early, evaluating the effectiveness of prevention and control measures, and informing public health decision-making.

2. Public Health Activities:

• Identifying priorities: Determining the public health issues that require surveillance.

• Planning: Developing a surveillance plan that outlines objectives, methods, resources, timelines, and personnel.

• Implementation: Carrying out the collection, analysis, and interpretation of information according to the established plan.

• Evaluation: Assessing the effectiveness of the surveillance system, identifying limitations, and making necessary adjustments.

3. Objectives:

• Understanding the current and potential patterns of disease: Surveillance helps identify trends, geographical distribution, seasonality, and risk factors associated with diseases.

• Knowing the natural history, spectrum of disease, and epidemiology of disease: Providing information about the transmission, progression, and impact of disease.

• Evaluating the effectiveness of preventive measures: Surveillance allows assessment of the impact of prevention and control programs.

4. Origins:

• Alexander D. Langmuir is considered the father of modern epidemiological surveillance. He emphasized the importance of systematic data collection and analysis for public health decision-making.

5. Types of Surveillance:

• Epidemiological surveillance: Monitoring health status within a population.

• Medical surveillance: Monitoring individuals who may have been exposed to a disease.

6. Types of Epidemiological Surveillance:

• Passive surveillance through disease and hospital reporting: This is the oldest form of surveillance, relying on voluntary reporting and passive data collection. While it can provide basic information about disease outbreaks, it can be prone to underreporting.

• Secondary surveillance: This system relies on analyzing data already collected from existing health databases. It provides insights into long-term trends and patterns.

• Active surveillance: This involves proactively seeking out data through surveys, interviews, and direct contact with individuals. It can be more resource-intensive but provides more accurate and timely information.

• Repeated cross-sectional surveys: Conducting surveys at specific intervals to track changes in health status.

• Targeted surveillance: Focusing on high-risk areas or populations for specific diseases.

7. Types of Surveillance Based on Information Sources:

• Active surveillance: Collecting information from various sources, such as reports, surveys, and data collection efforts.

• Passive surveillance: Receiving information from voluntary reporting sources.

• Surveillance based on the inverse new case proportion: Using the proportion of new cases to estimate the true number of cases in a population.

• Surveillance based on secondary data: Utilizing existing data that has been collected, analyzed, and aggregated.

8. Advantages and Disadvantages of Surveillance Types:

• Passive surveillance:

• Advantages: Easy to implement, low cost.

• Disadvantages: Low efficiency, can miss cases.

• Surveillance based on the inverse new case proportion:

• Advantages: Provides information on the true number of cases.

• Disadvantages: Expensive and complex.

• Surveillance based on secondary data:

• Advantages: Suitable for monitoring chronic diseases and overall population health.

• Disadvantages: Requires long-term data collection.

9. Minimum and Maximum Number of Cases to Report:

• Minimum number of cases: 35 cases should be reported.

• Maximum number of cases: 135 cases should be reported.

10. Notifiable Diseases:

• 42 diseases: These are notifiable under the Ministry of Health’s Circular 54/2018/TT-BYT dated December 17, 2018.

• 43 diseases: Zika

• 44 diseases: COVID-19

11. Surveillance Systems:

• Surveillance systems are categorized into four types:

• Animal population: Monitoring animal diseases.

• Environmental diseases: Surveillance of environmental conditions and their impact on health.

• Use of medicines and biological products: Monitoring the use of medicines and adverse effects of drugs.

• Diseases among students and workers: Monitoring the health of students and workers.

12. Steps to Establish a Surveillance System:

• 6 steps to establish a surveillance system:

• Consider the rationale: Clearly defining the purpose and requirements of surveillance.

• Define objectives: Setting clear goals for surveillance.

• Define case definition: Establishing clear diagnostic criteria for cases.

• Actions: Identifying necessary actions for data collection, analysis, and interpretation.

• Collaboration: Building collaborative networks for data collection.

• Implementation: Carrying out surveillance activities according to the planned framework.

13. Evaluating a Surveillance System:

• 6 criteria for evaluation:

• Simplicity: The surveillance system should be simple and easy to implement.

• Flexibility: The system should be flexible to adapt to changing disease patterns.

• Acceptance: The system should be acceptable to all stakeholders.

• Sensitivity: The system should be sensitive to changes in disease patterns.

• Representativeness: The system should represent the population being monitored.

• Timeliness: The system should provide timely information to support prevention and control efforts.

14. Factors Affecting Surveillance Systems:

• 9 factors:

• Population size:

• Access to information:

• Workload:

• Policymakers’ interest:

• Surveillance objectives:

• Personnel expertise:

• Usefulness of local data:

• Data used:

• Relevance:

Note:

• Epidemiological surveillance is a critical tool for monitoring public health, but it needs to be conducted systematically and scientifically to ensure effectiveness and reliability.

• The use of information and communication technologies (ICT) in surveillance can enhance efficiency and timeliness.

• Strong collaboration among agencies, organizations, and individuals is essential for comprehensive and effective surveillance systems.

Conclusion:

Epidemiological surveillance plays a vital role in monitoring public health, detecting disease risks early, evaluating the effectiveness of prevention and control measures, and informing public health decision-making. Building and operating an effective, timely, accurate, and transparent surveillance system is essential to ensure public health.