Public Health Surveillance Overview

Definition

• Ongoing, systematic collection, analysis, interpretation, and dissemination of data regarding health-related events.
• Used to reduce morbidity, mortality, and improve health.
• Traditionally for infectious diseases, now for chronic diseases, injuries, health services uptake, vector distribution, environmental hazards.

Importance

• Acts as the eyes and ears of public health.
• Uses:
  • Characterizing disease patterns.
  • Detecting outbreaks.
  • Suggesting hypotheses for further investigation.
  • Identifying cases for research.
  • Guiding disease control programs.
  • Setting public health priorities.
  • Evaluating health programs.

Basic Elements

1. Detection and Notification: Health services or laboratories detect and report health events.
2. Collection and Storage: Systematic collection and storage of data.
3. Analysis and Interpretation: Data needs to be analyzed and interpreted.
4. Dissemination: Information must reach the right people for appropriate action.

Types of Surveillance

Passive Surveillance

• Routine reporting of health data.
• Examples:
  • Notifiable diseases.
  • Health data registries (births, deaths, cancers, chronic diseases).
  • Data from healthcare providers.
• Advantages:
  • Generally inexpensive.
  • Provides baseline data, monitors trends and impact of interventions.
  • Can link different data sets for comprehensive health picture.
• Limitations:
  • Underreporting due to mild/asymptomatic illness, lack of access to treatment, inadequate laboratory facilities, logistical problems.

Active Surveillance

• Health data is actively sought out.
• Common during outbreaks.
• Examples:
  • Health teams visiting communities.
  • Serosurveillance (testing blood for markers).
  • Health surveys (community members, healthcare facilities, entire countries).
• Advantages: More complete and better quality data.
• Disadvantages: More resource-intensive.

Sentinel Surveillance

• Uses selected institutions/groups to provide health data on specific diseases/conditions.
• Useful for monitoring disease trends and detecting outbreaks.
• Limitation: Restricted to few groups, hence not useful for rare/uncommon diseases.

Rumor Surveillance

• Relies on unofficial sources (blogs, internet discussions, media, hearsay, social media).
• Alerts public health authorities to incidents/events requiring further investigation.

Syndromic Surveillance

• Monitors non-specific syndromes (fever, respiratory/gastrointestinal illness, medicine purchases, absenteeism).
• Aims for early identification of illness clusters.
• Relies on automated electronic methods.

Other Types

• Pred: Website for disease event reports.
• Global Public Health Intelligence Network: Internet-based early warning tool monitoring online news sources.

Characteristics of a Good Surveillance System

• Clearly Stated Objectives: Must have and achieve clear objectives.
• Simplicity: Easy to operate, straightforward case definitions.
• Flexibility: Accommodates changes with minimal resources.
• Data Quality: Complete, accurate, high-quality data.
• Acceptance: Accepted by participants.
• Sensitivity and Predictive Value: High sensitivity and positive predictive value.
• Validity: Measures what it intends to measure.
• Representativeness: Accurately represents health events regarding time, place, and person.
• Timeliness: Detects health events timely for appropriate action.
• Stability: Stable and available resources.
• Routine Evaluation: Surveillance systems must be routinely evaluated to meet objectives and serve public health function.
• Public Health Action: Provides useful information for public health action.

Summary

• Overview of public health surveillance: Definition, types, and characteristics of a good surveillance system.