Applied Epidemiology Flashcards
Name the 5 steps in investigating diseases
- Observation and recording of the natural occurrence of diseases
- Presentation and analysis of the observations
- Determine the cause of the disease
- Understand transmission, clinical signs, diagnosis – ‘disease ecology’
- The efficiency of different techniques to combat disease
Define epidemic
A level of disease in a population significantly greater than usual
Define endemic
Disease commonly found in, or restricted to a particular region, community or group of people
Define infectious disease
A disease due to an infectious agent.
Can be contagious or non-contagious
Define a contagious disease
A disease transmitted by direct or indirect contact with a host that is the source of the pathogenic agent
Define a communicable disease
A disease who’s causative agent can be transmitted from successive hosts to healthy subjects, from one individual to another
Define prevalence
A measure of disease occurrence
The proportion of individuals in a population who have the condition at a specified point in time
Define incidence
The number of new health-related events in a defined population within a specified period of time
Define morbidity
Any departure, subjective or objective, from a state of physiological or psychological well being.
Define mortality
The state of being subject to death.
What does R0 mean when talking about disease spread
Basic reproductive number of a disease
What is the value of R0 in an endemic disease
R0 < 1
When is R0 relevant
R0 is relevant only at the beginning of the spread of disease
What is the R number
Reproduction number at any time point during an outbreak
Describe a point source/common source epidemic and give examples
Rapid increase in cases
Tight clustering of cases, indicates common exposure
Examples - food poisoning, feed contamination
Describe a propagating epidemic and give an example
Slow then a rapid increase in cases
Starts with some initial cases then increases
Example - infectious disease
Give the 5 aspects of Hill’s criteria for establishing a cause of disease
Time sequence
Strength of association
Biological gradient
Consistency
Coherence or plausibility
Name 3 approaches commonly used to confirm a cause of disease
Structure/shape of the epidemic curve
Case-control studies
Cohort studies
What is a case-control study
Compare between cases and non-cases (diseased and non-diseased)
Look retrospectively at the differences in exposure to risk factors (i.e. calf shed, ice cream)
What is a cohort study
Look retrospectively or prospectively at individuals exposed and not exposed to risk factors (i.e. calf shed, ice cream) and see if they develop the disease
Give the 2 common measures of who is at risk of disease, and name the type of study they are commonly used for
Odds ratio => case-control studies
Relevant risk: risk ratio => cohort studies
What is meant by the risk difference (RD) of a disease
Comparison between risk of an outcome in an exposed group versus in the unexposed group (cohort)
What is meant by an odds ratio (OR)
Odds of the disease in the exposed group vs. with odds of the disease in the unexposed group
What is meant by the relative risk:risk ratio
The ratio of risk of disease in the exposed group to risk of disease in an unexposed group
Give examples of tests which sub-type genetic material for pathogen identification
PCR fingerprinting
DNA sequencing
RFLP (Restriction fragment length polymorphism)
Give advantages of using typing methods for ID of a pathogen (x5)
Increased sensitivity and specificity of diagnosis
Faster
Good for organisms that are hard to culture
Identification of carriers
Outbreaks can be detected earlier on
What is meant by disease ecology
Looking at how the disease affects the host, and how it is transmitted
What does disease ecology require
Knowledge of the pathogen
E.g. transmission routes, optimal environments, what ‘states’ animals in the population are in
Name the 4 possible ‘states’ an animal can be in with regard to susceptibility to disease
Susceptible - not got disease
Infected - have the disease
Recovered - have had the disease
Potentially susceptible again - can be reinfected
Name the 3 main factors in combatting disease
Disease prevention
Disease control
Disease eradication
What are the 3 groups that can be targeted in disease prevention and control and how
Host - increasing resistance/decreasing susceptibility
Environment - decrease pathogen transmission
Pathogen - decrease pathogen population
List 5 methods of reducing pathogen transmission in the environment
Restriction of host movement
Quarantining/isolation
Control of vectors
Biosecurity
ID those that need to be restricted
Name the 4 approaches to disease eradication and describe them
Test and removal - animals that test +ve are removed and slaughtered
Pre-emptive - Animals that have been exposed are slaughtered
Blanket culling - animals on contagious premised surrounding an infected farm are culled
Stamping out - combination of one of the methods above with other preventative methods
What additional factors should be considered when approaching disease control (x3, 1 extra)
Economics
Socioeconomics
Welfare
(mental health??)
Name the 4 post common food borne pathogens
Campylobacter
Clostridium perfringens
Norovirus
Salmonella
What does DALY stand for
Disability-adjusted life year
