Week 1 material

Question 1

what is a disease

Answer 1

a pathological condition of the body/tissues which can be seen through signs and symptoms

Question 2

what is an infectious disease and what can cause this disease

Answer 2

disease that is caused by an infectious agent

this disease can be passed on to others

the infectious agent can be bacteria, virus, fungus, or protozoan

Question 3

what is the epidemiologic triangle

Answer 3

encompasses the factors: host, agent, and environment

all 3 factors contribute to the result of a disease

they can specifically contribute to vector disease (infections that get spread via blood-sucking arthropods - mosquitos, ticks, fleas)

Question 4

what is the host

Answer 4

the individual where the agent produces the disease

the host’s intrinsic traits determines its risk to the exposure, its likelihood of having the disease, and its response to the causal effect

intrinsic traits include immunity, behaviour, and genetic predisposition

Question 5

what is the agent

Answer 5

the factor that can cause the disease

it needs to have these characteristics to be considered an agent
- infectivity
- pathogenicity
- virulence
- immunogenicity

examples of agents
- microbes
- nutrition
- poison
- allergens
- radiation
- physical trauma
- psychological experiences
- vitamin deficiencies

Question 6

what is the environment

Answer 6

the external conditions + influences that affect the living things

• includes the physical, biological, and social environments - they all contribute to the disease process
• the environment brings the host and agent closer together

Question 7

what are diseases that could be impacted by climate change

Answer 7

malaria - mosquitos can reproduce in warmer temperatures
lyme disease - caused by ticks

Question 8

how can climate change impact vector-borne diseases

Answer 8

for water-borne diseases - floods can help transport rodent-borne diseases

for fungal infections - droughts can help this to spread (?)

Question 9

what is science

Answer 9

a process that uses experiments + observations to find the answers to questions we have

• it’s a process
• uses observations and experiments
• draws conclusions from the observations + experiments
• draws conclusions based on evidence

Question 10

what are the steps to the scientific method

Answer 10

• make an observation
• identify the problem at hand
• research the problem
• create a hypothesis
• design an experiment
• collect + analyze the results
• come up with a conclusion - this can create a new hypothesis

Question 11

what must a scientific hypothesis be?

Answer 11

1. testable - the hypothesis can be tested using experiments or observational studies and the results from these tests can determine whether the hypothesis is rejected or not
2. falsifiable - data from experiment or study can reject the hypothesis or show that the hypothesis doesn’t explain the observation

Question 12

types of variables

Answer 12

Independent
- the variable that gets changed or manipulated in an experiment

Dependent
- the variable that gets measured in an experiment

Control
- the variable that remains constant in the experiment
- ensures the groups in the experiment are comparable
- ex. age

Question 13

what is the scientific process that occurs in lab research?

Answer 13

• design a vaccine immunogen (triggers the immune response)
• identify the drug-resistant bacteria’s biological mechanism
• map the evolutionary relationships between pathogens using molecular epidemiology

Question 14

what is the scientific process in public/population health research

Answer 14

• evaluate the ethics + impact of new vaccines and vaccine technology on public
• identify the risk factors for an infection done by a specific drug-resistant bacteria
• determine how much the pathogen has spread throughout the population

Question 15

what is epidemiology

Answer 15

the scientific study of diseases + health-related events in the population

Question 16

what are 2 types of epidemiological analyses

Answer 16

Descriptive = looks at the distribution of the disease in a population and the distribution’s basic features

• looks at the distribution pattern in the population

Analytic = tests a hypothesis about the cause of a disease by using a study to see how exposures relate to the disease - because studies can’t tell you about causation only correlation

Question 17

what do analytic epidemiologic studies do

Answer 17

• measures exposures and disease status of people to evaluate the association between the two
• these studies get used to evaluate the strength of association between exposure and disease status
• there are different analytic epidemiologic study designs
• deciding which one to use is dependent on the study population
• the key to this type of analysis is comparison

Question 18

What are the different analytic study designs?

Answer 18

cross-sectional
case-control
cohort
clinical trial

Question 19

what is a cross-sectional study

Answer 19

• information about exposure and disease status is collected all at once
• temporal: point in time

Question 20

what is a case-control study

Answer 20

• picks sample based on people who has disease and who doesn’t have disease
• looks back in time to collect information about exposure
• temporal: point in time or retrospective data
• best to use this design for when the disease is rare

Question 21

what is a cohort study

Answer 21

• picks sample based on people who have been exposed and who has not been exposed
• follows sample over time to see if they develop the disease or not
• temporal: follows subjects over time - either prospectively or retrospectively

Question 22

what is a clinical trial

Answer 22

• picks sample based on people who have the same disease status but have been exposed to different things
• sample gets followed over time to determine outcome
• temporal: follows subjects over time - prospectively

Question 23

for a case study - what would you expect the results to be if exposure was associated with disease

Answer 23

for the exposed group = there would be more people who would have the disease

for the non-exposed group = there would be more people who do not have the disease

Question 23

what are the 4 groups possible for cross-sectional study?

Answer 23

• been exposed + has disease
• been exposed + does not have disease
• not exposed + has disease
• not exposed + does not have disease

Question 24

what is the measure of association for and what are examples

Answer 24

a statistical value that shows the direction and relationship between exposure and outcome in each group (the 2 groups) It can not tell us if the exposure causes the disease odds ratio relative ratio

Question 25

what is odds ratio

Answer 25

the odds of disease among group that is exposed/the odds of disease among people that have not been exposed AD/BC OR =1- there is NO association between exposure and outcome OR > 1 - exposure is associated with high odds of outcome OR < 1 - exposure is associated with low odds of outcome higher the odds ratio - the more association there is between exposure and outcome

Question 26

what are some explanations for the association between exposure and outcome?

Answer 26

- there actually is a cause and effect - real cause and effect - by chance - there's bias in how you designed the study - there's confounding variables - the association is due to the differences between the 2 groups that could affect their risk of developing the outcome - eg. group 1 - young mice with vaccine group 2 - old mice with no vaccine young mice found to have a better immune system could be due to age (confounding) vs. the vaccine - reverse causation - Y causes X

Question 27

what is the Bradford Hill Criteria of Causation

Answer 27

it helps to determine if the association between the exposure and outcome is due to causation rather than by chance or bias it helps to determine if the exposure is the cause of the outcome rather than by chance - it increases the likelihood of there being a cause and effect relationship - Temporality: cause comes first and then effect - Strength of Association: stronger the association = more likely the relationship is causal - Consistency: consistent findings from different studies and populations strengthens the likelihood that the relationship is causal - Dose-response relationship: greater exposure = greater the incidence of the disease (disease is occurring more often in the population?) - Biological Plausibility: if there's a reasonable biological mechanism between exposure and disease known - this can increase the likelihood of there being a causal relationship - Specificity: if the exposure influences a specific outcome or population with no other explanation - Coherence: the findings between epidemiology and lab align with each other are draw to the same conclusion - Experiment: causation is more likely if the evidence is based on randomized experiments - Analogy: if there is known strong evidence of a casual relationship between a specific exposure and outcome - researchers should be more accepting of weaker evidence of there being a causal relationship between a similar exposure and outcome

Question 28

what is a randomized trial and why use randomization

Answer 28

- assigns exposure at random - randomization allows for the groups to be compared based on the factors related to the outcome - factors can be known or unknown - age, severity of illness, etc.

Question 29

how do we make sure the scientific process is followed?

Answer 29

- peer review: results are run by the experts to ensure the results are valid and presented fairly - retraction: when there are major mistakes in a already published article and authors, reviewers, editors, or readers question the validity of the article's findings - it gets retracted