week 1 material Flashcards
what is a disease
a pathological condition of the body/tissues which can be seen through signs and symptoms
what is an infectious disease and what can cause this disease
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
what is the epidemiologic triangle
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)
what is the host
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
what is the agent
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
what is the environment
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
what are diseases that could be impacted by climate change
malaria - mosquitos can reproduce in warmer temperatures
lyme disease - caused by ticks
how can climate change impact vector-borne diseases
for water-borne diseases - floods can help transport rodent-borne diseases
for fungal infections - droughts can help this to spread (?)
what is science
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
what are the steps to the scientific method
- 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
what must a scientific hypothesis be?
- 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
- falsifiable - data from experiment or study can reject the hypothesis or show that the hypothesis doesn’t explain the observation
types of variables
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
what is the scientific process that occurs in lab research?
- 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
what is the scientific process in public/population health research
- 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
what is epidemiology
the scientific study of diseases + health-related events in the population
what are 2 types of epidemiological analyses
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
what do analytic epidemiologic studies do
- 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
What are the different analytic study designs?
cross-sectional
case-control
cohort
clinical trial
what is a cross-sectional study
- information about exposure and disease status is collected all at once
- temporal: point in time
what is a case-control study
- 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
what is a cohort study
- 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
what is a clinical trial
- 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
for a case study - what would you expect the results to be if exposure was associated with disease
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
what are the 4 groups possible for cross-sectional study?
- been exposed + has disease
- been exposed + does not have disease
- not exposed + has disease
- not exposed + does not have disease
what is the measure of association for and what are examples
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
what is odds ratio
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
what are some explanations for the association between exposure and outcome?
- 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
what is the Bradford Hill Criteria of Causation
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
what is a randomized trial and why use randomization
- 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.
how do we make sure the scientific process is followed?
- 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
