Complete Rationales 2026-2027
Updated.
Epidemiology - Answer study of the FREQUENCY, DISTRIBUTION and DETERMINANTS of health
and disease, and the application of this to CONTROL health problems
Health - Answer State of physical, mental, social well-being, not merely the absence of disease
Disease - Answer derangement in function of the whole body of the host or any of its parts
Primary Prevention - Answer occurs before the onset of disease, focuses on education and
protection
Secondary Prevention - Answer early detection of the disease through screening
Tertiary Prevention - Answer addressing results of clinical illness in order to lessen impact of
the disease
Who is Dr. James Lind - Answer Conducted first ever randomized control study to develop
treatment for scurvy
Who is sir P. Pott - Answer Made earliest account of cause and effect linkage for an
occupational carcinogen in chimney sweeps
What are the components of the epidemiological triad - Answer Host, agent, environment:
combination of the three determines impact of disease
Direct-horizontal transmission - Answer between members of the same species from person-
person
Indirect-horizontal transmission - Answer between members of the same species through
ingestion, aerial via fomites or latrogenic (via medical exam/ treatments)
Vertical transmission - Answer from mother to embryo
,List the 4 stages of disease development - Answer (1) susceptibility (2) pre-symptomatic
disease (3) clinical disease (4) disability/ recovery
Latent Period - Answer Time between exposure and being able to detect disease (between
stage 1 and 2 of disease development)
Incubation Period - Answer Time between being exposed and onset of clinical signs (between
stages 1-3 of disease development)
Endemic - Answer habitually present at an expected level
Epidemic - Answer disease that appears as new cases at a rate which exceeds what's normally
expected
Pandemic - Answer disease that is widespread over a large area (worldwide)
Sporadic - Answer only occurs occasionally
Innate immunity - Answer natural (skin, white blood cells, stomach acid)
Naturally acquired active immunity - Answer when a person is exposed to a live pathogen,
develops disease and becomes immune via primary immune response
Naturally acquired passive immunity - Answer during pregnancy
Artificially acquired active immunity - Answer induced by vaccines which stimulates primary
response without causing symptoms
Artificially acquired passive immunity - Answer short-term immunization with an injection of
antibodies
Herd immunity - Answer balance between number of people susceptible to disease and the
number of people not susceptible - infectious agent has to be restricted to one host species and
relatively direct, infectious must induce solid immunity and you need random mixing of
individuals
Bias - Answer systemic error in design, conduct or analysis of a study that results in the
mistaken estimate of an exposures effect on the risk of disease
, Random error - Answer due to sample/ chance and can be fixed with an increase in sample
size
Direct Causation - Answer indicates a factor directly causes a disease or health outcome
without any steps in between
Indirect Causation - Answer indicates a factor causes disease but requires an intermediate step
3 types of Bias - Answer selection, information, confounding
Necessary and sufficient causal relationships - Answer factor needs to be there for disease to
develop and it alone can cause disease (if you remove it, remove disease)
Necessary but not sufficient causal relationships - Answer factor needs to be there for disease
to develop but requires other factors (reliant on other factors, can't do it by itself)
Sufficient but not necessary causal relationships - Answer Factor alone can cause disease, but
other factors can also cause disease so if you remove the factor you don't remove the disease
Neither sufficient nor necessary causal relationships - Answer Factors cannot cause disease
alone, and are also not the only factors that can cause disease
How do you know if an organism causes a disease? (3) - Answer organisms is always found
within disease, not found with any other disease and when isolated from one who has the
disease can cultured still produces the disease
9 considerations for if an association is causal (TSDRBACCS) - Answer temporal relationship,
strength of association, dose-response relationship, replication of findings, biological
plausibility, consideration of alternate explanations, cessation of exposure, consistency with
other knowledge, specificity
Selection bias - Answer bias in the way cases, controls, exposed and non-exposed groups are
selected such that apparent association is observed
4 types of selection bias - Answer Non-response
Exclusion: investigators applying eligibility criteria
Loss to follow-up: participants withdraw