Epidemics: Definitions and Types

Definition and Types of Epidemics

• Three major types of epidemics: Progressive, Endemicity, and Pandemic.

Progressive Epidemic

• Characterized by a case serving as a source, leading to subsequent cases.
• Epidemic curve features progressively larger peaks, indicating advancing severity of disease.

Endemicity

• Signifies ongoing presence of a disease in a specific geographic area or population.
• Example: Malaria is endemic in tropical regions.

Pandemic

• An epidemic that spreads across large regions, such as multiple continents or worldwide.
• It involves a widespread endemic disease that does not stabilize but spreads further.

Sporadicity

• Refers to diseases occurring infrequently and irregularly.

Hyperendemicity

• Indicates persistent, high levels of disease occurrence within a population.

Secular

• Relates to the geographical distribution of diseases over time.

Surveillance

• Systematic and ongoing data collection and analysis for public health monitoring.
• Active surveillance involves direct data collection from affected areas.
• Passive surveillance collects data through reports and communication without physical presence.
• Sentinel surveillance collects specialized data from qualified personnel about specific diseases.

Common Sources of Epidemics

• Common-source outbreaks arise from exposure to a single infectious agent or toxin.

Point Source Epidemic

• Exposure is brief and simultaneous; cases develop within one incubation period.
• Epidemic curve exhibits a rapid rise and fall, typically with one peak (e.g., food poisoning).

Continuous Common Source Epidemic

• Infection spreads from person to person, or via vectors, lasting longer than point-source outbreaks.
• Example: Malaria is propagated through mosquito transmission.

Intermittent Common Source

• The epidemic curve reflects the irregular, intermittent nature of the exposure.

Epidemic Preparedness

• Essential measures under different headings such as early warning, early detection, notification, and preparedness action plans.

Early Warning

• Timely surveillance systems provide data on epidemic-prone diseases prompting public health interventions.
• WHO improves surveillance to capture changing epidemiology for potential outbreaks.

Early Detection

• Involves recognizing significant increases in disease incidence above expected levels through routine reporting.
• Large outbreaks can be detected via health service utilization or media reports.

Notification

• Statutory reporting requirement for specified infectious diseases to public health authorities.
• Notification systems prioritize diseases needing prompt control action.

Preparedness Plan of Action

• Should be tailored based on previous epidemic information, emphasizing community education and organized resources.

Identification and Reporting of Priority Diseases

• Use standardized case definitions for reporting suspected priority diseases.
• Update surveillance procedures, distribution of reporting forms, and laboratory networks for effective monitoring.

Analysis of Disease Surveillance Data

• Define data management requirements and deadlines for reporting.
• Links with healthcare facilities are crucial for effective disease tracking.

Provincial and District Epidemic Committees

• Committees at different levels confirm reported events and assess urgency to implement control measures.
• Responsibilities include reporting essential information up to national levels.

Responding to Outbreaks

• Mobilizing resources and personnel is key for effective public health response.

Monitoring and Evaluating Disease Surveillance

• Evaluate existing indicators and propose objectives for improvement in the upcoming year.
• Assess effectiveness and address issues to enhance surveillance and response systems.

Activity

• Evaluate whether outbreaks stem from a single source or common source and assess disease transmission dynamics.