W11 Epidemiology

Acknowledge the people of the Kulin Nations on whose land the presentation takes place
Pay respects to their Elders: past, present, and emerging.

Definition: The World Health Organization defines public health as "the art and science of preventing disease, prolonging life and promoting health through the organized efforts of society."

Three Domains of Practice:
- Health Protection: Communication disease control and environmental health.
- Health Improvement: Health promotion, population health, preventive health.
- Healthcare Quality Improvement: Health services quality assurance; innovation and improvement in health care.

Health Protection Branch is part of the Victorian Department of Health.

Split into sections: Environment, Communicable Disease, and Strategy.
Communicable Diseases Section:
- Built on a notification system for infections.
- Urgent Notifiable Diseases: Immediate reporting required (e.g., measles, hepatitis A, rabies).
- Routine Notifiable Diseases: Written notification within 5 days (e.g., influenza, pertussis).
Notification range: 80,000 to 120,000 per year.
Managed by a team of 20 epidemiologists, 16 public health officers, and 4 doctors.

Outbreak: More cases than expected of a specific disease among a specific group in a given area during specific time.
Epidemic: More cases than usual; a synonym for outbreak but typically larger.
Pandemic: Global epidemic ("Pan-" means "all").
Cluster: Aggregation of cases; smaller than an outbreak.
Endemic: Regular occurrence of a disease within a certain area.

Ebola Virus Disease in DRC (2018-19)
- Second largest in history; 3,004 cases and 2,006 deaths.
- Significant risk concentrated in the DRC with potential spread to Uganda and Rwanda.
- Declared a Public Health Emergency of International Concern (PHEIC) on July 17, 2019.
- Ebola: viral hemorrhagic fever; not contagious until symptomatic; spread by contact with bodily fluids.
Measles in Victoria (May-June 2019)
Hepatitis A in Victoria (2017-2020)

Enhanced surveillance and genomic analysis of isolates.
Vaccination offers targeting at-risk populations (MSM, PWID, rough sleepers, adult prisoners).
Implement targeted communication campaigns and advisories.

New infectious agents emerging from environments/sources.
Increased travel introducing susceptible populations to endemic pathogens.
Effective transmission routes changing with climate change (new mosquito species).

Goals:
- Identify the pathogen/source
- Control (stop new cases)
- Prevent future outbreaks
- Learn about disease
- Training opportunity for public health personnel.

Outbreaks identified in diverse settings (aged care, schools, workplaces).
Core principles remain consistent:
- Identify pathogen/source, control the spread, and prevent future occurrences.
Components include case management, contact management, environmental management, active case finding/testing, stakeholder management, and community engagement.

Epidemiology: Core epidemiological methods apply in outbreak investigation.
Environmental and Laboratory Analysis: Includes genomic studies and risk assessments.
Use of GIS: Geographic Information Systems for spatial analysis.

Prepare for Field Work
- Assess risk factors and supplies needed.
- Determine team composition and roles (e.g., statistical advisors).
- Administrative considerations related to travel and communication.
Verify/Establish Existence of an Outbreak
- Must be defined as “more cases than usual”; specify community/region and time.
- Use surveillance data to understand baseline patterns of disease.
Confirm/Verify Diagnosis
- Review clinical/laboratory findings to confirm specific pathogens.
Define/Identify Cases
- Establish case definitions based on clinical features, person, place, time, and laboratory results.
Describe/Orient Data
- Create epidemic curves and maps to visualize the outbreak context (time, place, person).
Develop Hypotheses
- Generate possible sources and modes of transmission.
Evaluate Hypotheses
- Test against data collected during investigation.
Refine Hypothesis/Perform Additional Studies
Implement Control and Prevention Measures
- Take immediate action based on findings to halt the outbreak.
Communicate Findings
- Report to stakeholders, media, and public throughout; prepare formal reports and publications.

Types of Surveillance:
- Passive: Wait for occurrences.
- Mandatory notifications.
- Active: Proactively search for cases.
- Sentinel surveillance for early detection in targeted populations.
Innovative surveillance: Leveraging social media, public reports, and various digital platforms for data collection.

Odds Ratio (OR): Measure of association computed as: $OR = \frac{ad}{bc}$
- Interpretation: If OR = 1, no association; if CI includes 1, not statistically significant.
- Example: OR of disease in exposed group versus non-exposed group.

Case-Control Studies:
- Defined groups with cases and controls; look back at past exposure.
- Suitable for rare diseases, but subject to recall bias and issues with control selection.
Cohort Studies:
- Follow groups over time based on exposure; can measure disease incidence.
- Allow for multiple outcomes but can be costly and require lengthy follow-up.

Acknowledge contributors and institutions involved in the public health responses and presentations.
Follow up questions or clarifications regarding outbreak investigation methodologies and principles are encouraged.