Surveillance Systems

Introduction to Surveillance - Disease Detectives

• Definition: Ongoing, systematic collection, analysis, interpretation, and dissemination of health data for effective public health action.
• Purpose:
  • Detect outbreaks & monitor disease trends.
  • Evaluate interventions (e.g., vaccines).
  • Guide health policy & resource allocation.
• Objectives:
  • Early warning of potential health threats.
  • Inform evidence-based policy making.
  • Optimize resource allocation.
• Types: 📌 Mnemonic: "P.A.S.S. D.R."
  • Passive: Routine reporting by health facilities.
  • Active: Health authorities actively seek out data.
  • Sentinel: Data from selected sites/providers for specific conditions.
  • Syndromic: Tracks symptoms/health data before diagnosis.
  • Digital: Uses online data (social media, news alerts).
  • Rumor: Investigates unofficial reports or public concerns.

⭐ Sentinel surveillance is often used for influenza-like illness (ILI) and severe acute respiratory infections (SARI).

Process of Surveillance - The Watchful Cycle

A continuous, systematic cycle for timely public health action.

• 1. Data Collection: Gathering relevant health data.
  • Sources: Notifiable diseases (IDSP), lab reports, hospital records, surveys (NFHS).
  • Methods: Forms, interviews, digital platforms (e.g., IHIP).
• 2. Data Collation & Analysis: Organizing and examining data.
  • Collation: Systematic data aggregation.
  • Analysis: By time, place, person; calculating rates (incidence, prevalence) & ratios.

  ⭐ Analysis by time, place, and person is crucial for identifying patterns in disease occurrence.

• 3. Interpretation: Making sense of analyzed data.
  • Identifying changes in disease frequency, trends, or outbreaks.
  • Comparing current data with baseline levels.
• 4. Dissemination: Communicating findings to stakeholders.
  • Methods: Reports, bulletins, alerts to health authorities, policymakers, community.
• 5. Public Health Action: Implementing evidence-based interventions.
  • Actions: Control measures (vaccination, sanitation), policy changes, resource allocation, further investigation.

Surveillance Systems in India - Our Health Sentinels

• Integrated Disease Surveillance Programme (IDSP): For outbreak detection & response.
  • Objectives: Early warning, rapid response to outbreaks.
  • Components: Central, State, District units; Labs; IT; Training.
  • Reporting: Weekly reporting (epidemic-prone diseases). Forms:

    Form	Captures
    S	Suspected cases
    P	Probable/Presumptive cases
    L	Laboratory-confirmed cases

  • ⭐

    Under IDSP, 'S' form is for suspected cases, 'P' form for probable/presumptive cases, and 'L' form for laboratory-confirmed cases.

  • Data Flow (IDSP):

• National Centre for Disease Control (NCDC): Apex body for IDSP, outbreak investigation.

• Key National Surveillance Programs:

  • AFP Surveillance: For Polio (target: AFP rate >2/100,000 <15 yrs).
  • Measles & Rubella Surveillance.
  • HIV Surveillance: (NACO/SACS).
  • RNTCP: (TB).
  • NCD Surveillance: (Cancer, Diabetes, Hypertension registries).

Attributes & Evaluation of Surveillance - System Report Card

Key attributes assess surveillance system quality:

Key attributes assess surveillance system quality:

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| Specificity | Excludes non-cases; $TN / (TN + FP)## Attributes & Evaluation of Surveillance - System Report Card

Key attributes assess surveillance system quality:

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| PVP | Proportion of positives that are true; $TP / (TP + FP)## Attributes & Evaluation of Surveillance - System Report Card

Key attributes assess surveillance system quality:

| | Representativeness| Accurate picture of disease in population | | Timeliness | Speed of detection & reporting | | Completeness | Proportion of all cases detected | | Flexibility | Adaptability to new diseases/conditions | | Acceptability | Willingness to participate | | Simplicity | Ease of operation |> ⭐ Timeliness is a critical attribute for effective outbreak response.

📌 Mnemonic: Sensitive Systems Provide Relevant, Timely, Complete, Flexible, Acceptable, Simple data (SSPRTCFAS).

High‑Yield Points - ⚡ Biggest Takeaways

• IDSP is India's core program for disease surveillance and outbreak detection.
• Key types: Passive (routine reporting), Active (proactive search), Sentinel (select sites, quality data).
• Zero reporting in passive surveillance confirms system vigilance and data completeness.
• Notification of specified diseases is a legal mandate for public health action.
• Surveillance involves: Case definition, data collection, analysis, interpretation, and dissemination.
• Event-Based Surveillance (EBS) detects early signals of unusual health events.
• IHR (2005) requires robust national surveillance for global health security.