Disease Surveillance Overview

DISEASE SURVEILLANCE STUDY NOTES

WHAT IS DISEASE SURVEILLANCE

  • Definition (WHO): Disease surveillance is the ongoing systematic collection, analysis, and dissemination of data on diseases of public health importance, enabling timely action to prevent or halt disease spread.
  • Definition (CDC, 1986): Involves the ongoing systematic collection, analysis, and interpretation of health data essential for public health practice planning, implementation, and evaluation, closely tied to timely data dissemination to stakeholders.
  • Primary Functions:
    • Guides Disease Control Activities: Aids in measuring the impact of immunization services.
    • Application of Data: The final link in the surveillance chain involves applying collected data to prevent and control diseases.

IMPORTANCE OF DISEASE SURVEILLANCE

  • Epidemiological and Clinical Tool:

    • Assists in establishing baseline disease rates and detecting changes.
    • Estimates prevalence, time trends, and geographic distribution of health issues.
    • Aids in understanding disease progression and associated risk factors.
    • Generates hypotheses around causes and transmission.
    • Fosters research initiatives on disease causation, control, and prevention.

  • Practical Uses:

    • Predicts/detects disease outbreaks for containment.
    • Identifies high-risk populations and areas for focused interventions.
    • Monitors progress toward disease eradication and control.
    • Identifies system performance issues for quality improvement.
    • Assesses disease frequency and burden in communities.
    • Documents immunization program effectiveness on disease impact.
    • Identifies circulating strains of pathogens (serotypes, genotypes, subtypes).

DISEASE SURVEILLANCE BASED ON CONTROL OBJECTIVES

  • The type of surveillance needed varies based on the disease attributes and objectives, which can include:
    • Control (e.g., Diphtheria, Hepatitis B)
    • Elimination (e.g., Neonatal Tetanus, Measles)
    • Eradication (e.g., Polio, Smallpox)

NOTIFIABLE DISEASES

  • Definition: A notifiable disease is one that must be reported to public health authorities by law to facilitate monitoring.

BURDEN OF ILLNESS PYRAMID

  • The burden of illness pyramid model helps understand the reporting of diseases and illustrates the steps that need to be taken for an illness episode to be registered in surveillance:
    • Population Exposures: Members of a population are exposed to a pathogen.
    • Illness: Some exposed may fall ill.
    • Medical Care: Some of the ill seek medical help.
    • Specimen Collection: Samples are collected from the ill.
    • Laboratory Testing: Specimens are tested for pathogens, confirming cases.
    • Reporting: Confirmed cases are reported to health departments.

TYPES OF SURVEILLANCE

  • Passive Surveillance:

    • Regular disease data reporting by institutions without active case searches.
    • Relies on clinical and laboratory cooperation to report diseases to health departments.
    • Often includes zero reporting when no cases are found, ensuring operational confidence.

  • Sentinel Surveillance:

    • Focused on high-quality data collection about specific diseases through selected reporting sites.
    • Used when passive data cannot provide sufficient quality data.
    • Ideal for monitoring specific diseases and trends.

  • Active Surveillance:

    • Involves direct visits and engagement with health services to actively find suspected cases.
    • More resource-intensive and effective for diseases targeted for eradication or during outbreaks.
    • Enhances case detection timeliness and accuracy.

  • Comparison of Surveillance Methods:

    • Passive Surveillance: Widely covering areas but relies heavily on reporting completeness.
    • Sentinel Surveillance: High quality data, but limited in scope.
    • Active Surveillance: Effective in targeted situations, needs substantial resources.

SETTING UP SURVEILLANCE SYSTEMS

  • Passive Surveillance:

    • Identify and list health facilities likely seeing cases.
    • Educate providers on reporting formats and timelines.
    • Ensure systems support zero reporting for comprehensive monitoring.

  • Sentinel Surveillance:

    • Select institutions with geographic relevance and expertise.
    • Involve voluntary participation; create standardized reporting formats.
    • Use feedback systems for tracking reporting adequacy.

  • Active Surveillance:

    • Appoint surveillance officers responsible for site investigations.
    • Engage healthcare providers and inform them about the importance of active reporting.

CASE DEFINITIONS FOR DISEASE IDENTIFICATION

  • Importance:

    • Standardized criteria help in accurate classification of cases for reporting and investigation.
    • Include clinical criteria, laboratory confirmation, epidemiological factors, and geographical location.

  • Types:

    • Suspected: Initial identification based on symptoms.
    • Probable: Meets clinical criteria but lacks lab confirmation.
    • Confirmed: Laboratory confirmation of the case.

EXAMPLES OF CASE DEFINITIONS

  • Influenza:

    • Suspected: Fever (≥100.4°F) and cough.
    • Probable: Positive rapid test or close contact with a confirmed case.
    • Confirmed: Laboratory confirmation via PCR or culture.

  • Tuberculosis (TB):

    • Suspected: Persistent cough, weight loss, etc.
    • Probable: Positive tuberculin skin test without lab confirmation.
    • Confirmed: Microbiological confirmation of infection.

  • COVID-19:

    • Suspected: Acute respiratory symptoms and exposure.
    • Probable: Positive rapid antigen test.
    • Confirmed: Positive PCR test for SARS-CoV-2.

LIMITATIONS OF CASE DEFINITIONS

  • Contextual factors often not captured in definitions.
  • Balancing sensitivity and specificity can create challenges in accurately identifying cases.
  • Legal and administrative implications tied to specific definitions complicate practice.

INTEGRATED DISEASE SURVEILLANCE AND RESPONSE (IDSR)

  • Objective: Streamlines surveillance for multiple diseases, enabling better public health responses.
  • Functions:
    • Improve timely detection and prevention of outbreaks.
    • Enhance collaboration between health systems at all levels.
    • Develop rational resource use for effective public health interventions.

IDSR IN GHANA

  • Strategies:
    • Fit into national health objectives aimed at increasing healthcare access and quality.
    • Focus on epidemic-prone diseases like Cholera, Measles, and others targeted for eradication (e.g., Polio).
  • Support from MOH:
    • Development of technical guidelines, training manuals, and advocacy for resources.

CONCLUSION

  • Disease surveillance is critical for the control and prevention of outbreaks.
  • Clear, consistent case definitions are essential for effective public health practices.
  • Integrated approaches enhance efficiency and effectiveness in health systems.