Pathology
WEEK 1 – Module 1
INTRODUCTION TO EPIDEMIOLOGY
• Epidemiology =
- study of the distribution and determinants of health related states among
specified populations
- and the application of that study to the control of health problems
• broad idea = understanding macro level of disease and public health
- large scale population level
• Health related states à not specific to disease!!
- Can include road accidents, snake bites
§ Causation, distribution etc
• Distribution à where?
- Where à Uniform or random
- Who à all? Elderly? Young?
- When à seasonality
• Determinants à causes
- Biological
• Control à study in order to be able to cure/treat
POPULATIONS à INDIVIDUAL
• Public health programs
- Vaccine initiatives
§ Infant vaccination program
§ Generalized population vaccination program à eg. COVID19
vaccines
§ Directed at the individual but aimed to reach the general public on a
large scale
DISTRIBUTION
= concerned with frequency and pattern of health events
- Frequency – no. of cases in a population and the relationship of that number
to the size of the population
§ Why??
• Rate allows for comparison accounting for population size!!
• Why know the difference? How urgent is control, what is your
risk of contracting disease, how prevalent is the disease?
- Pattern – occurance of cases by time, place and person
§ Time = Seasonal, daily, annual
§ Place = geographic variation, urban/rural
§ Personal characteristics = demographic factors
• Age, sex, socioeconomic status, behaviors, environmental
exposures, genetics, personal hygiene (safe sex, sanitization),
co-morbidities
• Outbreak = noticeable but often small increase over the expected number of cases
• Epidemic = outbreak over a larger geographical area, larger than expected number
of cases occur in a short time in an area
, - Signals the breakdown of an equilibrium in disease frequency often resulting
from some change in environmental conditions
• Pandemic = epidemic spreads to more countries/regions of the world
- Epidemic occurring on a worldwide scale
• Feature of time and place rather than the actual disease
• Endemic = disease generally found in that area, “in the population”
- Eg. TB
§ Endemic to SA but would be an outbreak in other places eg USA
- Not necessarily mild!!!
§ Eg. COVID seems more mild due to vaccinations etc vs TB vaccine is
relatively poor
• Emerging infectious diseases = either new to the human population or has shown an
increase in prevalence in the past 20 years
Incidence = new cases of a disease
• Conveys information about the risk of contracting a disease
Incidence rate = cases per (usually 100 000) people
è Rubella = endemic and occurs whole period
o Week 35 – 41 = outbreak in KZN and Eastern cape
§ If had seen dramatic increase across all provinces, would classify as epidemic
§ If had spread to neighboring countries and beyond à pandemic
§ Unusually high numbers
è KZN = noticeable throughout graph
Prevalence = proportion of cases in the population at a given time (%)
• How widespread is the disease
,DETERMINANTS
• Biological
- Viruses
- Bacteria
- Parasites
- Fungi
• Social
• Environmental
• Political
• Economic
• Historical
- Infrastructure and background
• Environmental
CONTROL
• Healthy population
- Prevention!!
§ Vaccines
§ Clean water and sanitation
§ PPE
§ Decontamination of surfaces
§ Good ventilation
§ Physical distance
§ Food safety
§ Pest control
§ Better housing
§ education
, • Infection
- Diagnosis!!
§ Molecular diagnostic tests
§ Clinical diagnosis
§ Early diagnosis
• Disease
- Treatment!!
§ Drugs
• Prevent and treat
• Targeted vs supportive
TRACKING DISEASE
• Health surveillance
§ = epidemiological practice by which the spread of disease is
monitored in order to establish patterns of disease
§ =process/activity of continued watchfulness over a disease using
systematic collection, analysis and interpretation of health data
- Why necessary
§ Predict
§ Observe
§ Minimize harm
§ à critical in order to guide efforts for preventing + controlling disease
- Who conducts surveillance
§ Public health organizations
• National
o NICD
o CDC
• Global
o WHO
- How is it conducted
§ Health indicators of the burden of disease
• Hospitalization data
• Registration of deaths
• Notifiable diseases
o Certain diseases are required to be reported by
healthcare professionals
• Population surveys
• Sentinel sites
o Places selected across the country to represent certain
areas
§ Set health targets
- How is the data used
§ Measure incidence
§ Track trends/changes
§ Monitor and evaluate effectiveness of existing measures
§ Health service planning
§ Assess progress against health targets
§ Syndromic surveillance
• New types of infections won’t have a clinical test
• Look for common patterns in symptoms and signs
§ Stimulate research
WEEK 1 – Module 1
INTRODUCTION TO EPIDEMIOLOGY
• Epidemiology =
- study of the distribution and determinants of health related states among
specified populations
- and the application of that study to the control of health problems
• broad idea = understanding macro level of disease and public health
- large scale population level
• Health related states à not specific to disease!!
- Can include road accidents, snake bites
§ Causation, distribution etc
• Distribution à where?
- Where à Uniform or random
- Who à all? Elderly? Young?
- When à seasonality
• Determinants à causes
- Biological
• Control à study in order to be able to cure/treat
POPULATIONS à INDIVIDUAL
• Public health programs
- Vaccine initiatives
§ Infant vaccination program
§ Generalized population vaccination program à eg. COVID19
vaccines
§ Directed at the individual but aimed to reach the general public on a
large scale
DISTRIBUTION
= concerned with frequency and pattern of health events
- Frequency – no. of cases in a population and the relationship of that number
to the size of the population
§ Why??
• Rate allows for comparison accounting for population size!!
• Why know the difference? How urgent is control, what is your
risk of contracting disease, how prevalent is the disease?
- Pattern – occurance of cases by time, place and person
§ Time = Seasonal, daily, annual
§ Place = geographic variation, urban/rural
§ Personal characteristics = demographic factors
• Age, sex, socioeconomic status, behaviors, environmental
exposures, genetics, personal hygiene (safe sex, sanitization),
co-morbidities
• Outbreak = noticeable but often small increase over the expected number of cases
• Epidemic = outbreak over a larger geographical area, larger than expected number
of cases occur in a short time in an area
, - Signals the breakdown of an equilibrium in disease frequency often resulting
from some change in environmental conditions
• Pandemic = epidemic spreads to more countries/regions of the world
- Epidemic occurring on a worldwide scale
• Feature of time and place rather than the actual disease
• Endemic = disease generally found in that area, “in the population”
- Eg. TB
§ Endemic to SA but would be an outbreak in other places eg USA
- Not necessarily mild!!!
§ Eg. COVID seems more mild due to vaccinations etc vs TB vaccine is
relatively poor
• Emerging infectious diseases = either new to the human population or has shown an
increase in prevalence in the past 20 years
Incidence = new cases of a disease
• Conveys information about the risk of contracting a disease
Incidence rate = cases per (usually 100 000) people
è Rubella = endemic and occurs whole period
o Week 35 – 41 = outbreak in KZN and Eastern cape
§ If had seen dramatic increase across all provinces, would classify as epidemic
§ If had spread to neighboring countries and beyond à pandemic
§ Unusually high numbers
è KZN = noticeable throughout graph
Prevalence = proportion of cases in the population at a given time (%)
• How widespread is the disease
,DETERMINANTS
• Biological
- Viruses
- Bacteria
- Parasites
- Fungi
• Social
• Environmental
• Political
• Economic
• Historical
- Infrastructure and background
• Environmental
CONTROL
• Healthy population
- Prevention!!
§ Vaccines
§ Clean water and sanitation
§ PPE
§ Decontamination of surfaces
§ Good ventilation
§ Physical distance
§ Food safety
§ Pest control
§ Better housing
§ education
, • Infection
- Diagnosis!!
§ Molecular diagnostic tests
§ Clinical diagnosis
§ Early diagnosis
• Disease
- Treatment!!
§ Drugs
• Prevent and treat
• Targeted vs supportive
TRACKING DISEASE
• Health surveillance
§ = epidemiological practice by which the spread of disease is
monitored in order to establish patterns of disease
§ =process/activity of continued watchfulness over a disease using
systematic collection, analysis and interpretation of health data
- Why necessary
§ Predict
§ Observe
§ Minimize harm
§ à critical in order to guide efforts for preventing + controlling disease
- Who conducts surveillance
§ Public health organizations
• National
o NICD
o CDC
• Global
o WHO
- How is it conducted
§ Health indicators of the burden of disease
• Hospitalization data
• Registration of deaths
• Notifiable diseases
o Certain diseases are required to be reported by
healthcare professionals
• Population surveys
• Sentinel sites
o Places selected across the country to represent certain
areas
§ Set health targets
- How is the data used
§ Measure incidence
§ Track trends/changes
§ Monitor and evaluate effectiveness of existing measures
§ Health service planning
§ Assess progress against health targets
§ Syndromic surveillance
• New types of infections won’t have a clinical test
• Look for common patterns in symptoms and signs
§ Stimulate research
