EPIDEMIOLOGY
WEEK 1: Introduction to Epidemiology
Epidemiology study
Experimental
Observational
Distribution: Descriptive epidemiology
Determinant: Analytical
How?
Why?
Who?:characteristics of person
Where?: characteristics of place
When?: characteristics of time
Goals of Epidemiologic study
To explain
To describe
To predict
To control
To evaluate
Involves recording disease and possible causal factors
deals with frequency and the distribution of disease or risk factors in population
Application of descriptive epidemiology
To evaluate trends in disease, health, and risk factors such as smoking
• To determine if a health status is improving or getting worse
• To determine if new diseases are occurring, and provide a factual basis for evaluating public health programs and services
• To determine if existing programs are effective, or if new programs should be developed
analysis of observations using suitable diagnostic and statistical procedures
investigating the underlying causes of the pattern of disease or health outcome
CAUSES AND EFFECT
Natural History of Disease
progress of a disease process in an individual over time without intervention
Spectrum of disease: Disease may present with varying signs, symptoms and severity
4 stages of spectrum:
- Susceptibility stage (pre-disease) - exposure
- Sub-clinical or Inapparent stage- pathologic changes but disease did not manifest itself
- Clinical stage
- Recovery, disability or death stages
• Latent period (chronic): infection --> dev. of infectiousness
• Infectious period: time infected host can infect another susceptible host
• Non-infectious period: the host’s ability to transmit disease to other hosts ceases
• Incubation period: infection --> clinical disease dev.
Chain of Infection
Reservoir
Portal of exit
Modes of transmission
Postal of entry
Susceptible host
Direct
Indirect
WEEK 2:Causal Concept & Dynamics of Disease Transmission
Causality: relationship between cause (exposure) and effect (outcome)
Causality =/= Association
• Bias
• Chance
• Confounding
• Reverse causality
Theory of disease causation
Supernatural theory of disease: Disease is due to superpower e.g. gods, evil spirits
Theory of contagion: Spreading of disease by being close to or touching other people.
Miasmatic theory of disease causation: Disease is due to noxious air and vapors
Epidemiologic triad
Agent
Host
Environment
Web of causation: interaction between causes to the specific disease
Level of cause in WoC
• Macrolevel (social, economics, and cultural determinants)
• Individual level (personal, behavioural and physiological determinants)
• Microlevel (organ system, tissues, cellular and molecular determinants)
Basic reproduction number (Ro): number of cases of infection when one infected host is introduced to a susceptible population
Factors affecting Ro
Mode of disease transmission
Population density
Infectiousness of the agent
Course of disease (latent period, incubation period)
Risk factors: factor that associated with the health outcome
WEEK 5: DESCRIPTIVE AND ANALYTICAL
Study Design
Experimental
Obsevational
Randomized controlled trials
Quadsi-randomized trials
Descriptive
Analytical
Case report/series
Descriptive cross-sectional
cohort