Natural History of Disease

Question 1

Epidemiological Triad

Answer 1

For disease to occur, there is an interaction between environment, host, time, and agent
Time focuses on incubation or latency period

This is the advanced triangle:
Causative Factors, Groups or Populations and Their Characteristics, and Environment, Behavior, Culture, Physiological, Ecological Elements
If you have a simple model, you will come up with simple explanations
The truth is that causes for diseases are usually multifactorial and more complex

Question 2

Wheel

Answer 2

Biological, Social, and Physical Environments = outer wheel
Host is the middle wheel
Genetic core is the innermost wheel
Emphasizes that there are multiple factors that cause disease
Depending on the disease, the size of the model varies

Question 3

Web of Causation

Answer 3

Multifactorial POV

International Factors, National/Regional/ Community/Local, Work/School/Home, Individual, and Population

Question 4

Casual Pie

Answer 4

Necessary cause: found in all cases
Component cause: needed in some cases
Sufficient mechanisms: combination of necessary, competent, and sufficient causes that make disease inevitable in an individual

A given disease can have multiple sufficient mechanisms

Question 5

Infectivity, Pathogenicity, and Virulence

Answer 5

Infectivity: ability of agent to infect individuals that are exposed

Pathogenicity: ability of agent to produce clinical disease

Virulence: ability of agent to cause severe clinical outcome such as death

Question 6

Chain of Transmission

Answer 6

Mode of Transmission, Portal of Entry, Susceptible Host, Causative Agent, Reservoir, and Portal of Exit

Question 7

Robert Koch’s Criteria

Answer 7

Must be present in every case of the disease.
Must be isolated from the host with the disease and grown in pure culture.
The specific disease must be reproduced when a pure culture of the bacteria is inoculated into a healthy susceptible host.
Must be recoverable from the experimentally infected host

Problem with Koch’s criteria: not all bacterial is harmful or able to be grown in culture, not everyone who is exposed will develop the disease, and cannot use this for every type of disease

Question 8

Contributory/Component Criteria

Answer 8

Cause then Effect

If you alter cause then you alter effect

Question 9

Bradford Hill’s Criteria

Answer 9

Strength of association
Consistency with other studies
Exposure precedes disease
Biological plausibility
Dose- response effect

The above 5 criteria are what dictate the effect of the cause

Question 10

Levels of Prevention: Primordial

Answer 10

Avoid emergence and establishment of social, economic and cultural patterns of living that are known to contribute to elevated risk of disease

General approach to health improvement of social and physical environment

Ex. ban smoking or alcohol

Question 11

Levels of Prevention: Primary

Answer 11

During stage of susceptibility before exposure; before it occurs

Modifiable risk factors
changing or eliminating the agent
changing the condition of the host
changing the environment

Health promotion
Counseling, education, advocacy
Organizational needs
Resources

Ex. immunizations, behavioral changes, injury prevention

Question 12

Levels of Prevention: Secondary

Answer 12

During stage of subclinical disease; have the risk factors but not the disease yet

Early diagnosis
Case-finding, individual and mass screening programs that are universal or targeted
Prompt treatment and adequate primary medical care to prevent progression to apparent disease

Ex. Routine blood sugar testing for people over 40 to detect diabetes.
Pap test to screen for cancer of the cervix

Question 13

Levels of Prevention: Tertiary Prevention

Answer 13

During stage of clinical disease; already have the disease

Limitation of disability
adequate treatment to arrest/eradicate disease process
services to limit disability and prevent death

Rehabilitation
Terminal care