Outbreak Investigation

Introduction

• Definition of an Outbreak
  • More cases of illness than normally expected in a population, area, and time.
  • Sometimes used interchangeably with epidemic.

Outbreak Detection

• Surveillance Methods
  • Passive Surveillance: Monitoring routinely collected health data.
  • Active Surveillance: Actively seeking out health information.
  • Sentinel Surveillance: Selected groups or institutions provide health data.
  • Syndromic Surveillance: Monitoring illness syndromes.
  • Other sources: Social media, news, hearsay.

Outbreak Investigation Steps

1. Confirming the Outbreak

   • Compare current illness levels with baseline levels.
   • Rule out other causes like increase in testing or population growth.
   • Verify diagnosis through clinical and laboratory findings.

2. Describing the Outbreak

   • Determine who is affected, where and when it occurs.
   • Case Definition: Criteria for classifying someone as a case, including time, place, person, clinical, and laboratory features.
   • Systematic search and data collection on cases using questionnaires.
   • Descriptive Analysis:
     • Time: Epidemic curve shows disease development over time.
       • Point-Source Outbreak: Sharp rise and fall in cases (e.g., contaminated dish).
       • Propagated Outbreak: Series of peaks, person-to-person spread.
     • Place: Geographical spread, identifying clusters using mapping tools.
     • People: Describing affected individuals by age, sex, occupation, ethnicity.

3. Determining the Cause

   • Developing a hypothesis on likely cause from previous steps.
   • Analytical Epidemiological Study:
     • Cohort Studies
     • Case-Control Studies
   • Environmental Investigation: Identifying factors contributing to outbreak.
   • Laboratory Analysis: Microbiological information to confirm the hypothesis.

4. Implementing Control Measures

   • Targeting any stage of transmission pathways (agent, host, environment).
   • Examples:
     • Behavioral: Mosquito repellents.
     • Vaccinations during outbreaks.
     • Medication (e.g., ivermectin for scabies).
     • Environmental: Insecticide spraying, improving water quality.
     • Infection Control: Isolation, PPE, disinfection.
   • Health Education: Guidance for sick and healthy individuals to prevent spread and infection.
   • Active surveillance post-control measures to ensure effectiveness.

Communication in Outbreak Management

• Ensuring accurate, timely information dissemination internally and externally.
• Public communication to reduce anxiety, confusion, and misinformation.
• Media partnership for outbreak communication.
• Sharing information through online forums or scientific journals.

Declaring an Outbreak Over

• Considered over when no cases occur after two incubation periods.

Summary

• Overview of infectious disease outbreaks, detection, investigation steps, and control methods.