Epidemiology 1-2

Veterinary Epidemiology VMCVM

What is Epidemiology?

the determinant of health or related states or eventsin specified populations, and the application of this study to control health problems.

Epidemiology focuses on specified ___ rather than ___

populations; individual animals

The epidemiology triad includes…

agent, host, and environment

The “host” can be described as

“what” gets infected

The “environment” can be described as

where the host and agent meet

The “agent” can be described as

what causes disease

Factors of the host include

age

species

genetics

immune status

behaviors

physiological state

Physiological state is described as

the body’s current functional conditions/health

Factors of the agent include

microparasites

macroparasites

toxins

physical injury

Factors of the environment include

weather

sanitation

management

built environments

social determinants

vectors

social determinants can be described as

social and living circumstances

Vector defintion

living things that carry germs

What is the “Epidemic Curve”?

a graph that plots how many animals become sick in different times (days)

What is a “Flatten Curve”

shows the same # of subjects but over a longer period of time(days)

Define Prevalence

Present or current cases cases

How do we calculate Prevalence

number of all current cases ÷ entire population at risk

Define Incidence

Incoming or new cases

How do we calculate Incidence

number of new cases ÷ entire population at risk

What are the types of epidemin plots that can be shown (4)

sporadic

endemic

epidemic point-source

epidemic propagating epidemic

Define sporadic

disease occurrence consists of occasional, scattered cases with irregular increases and decreases

Define endemic

cases with a steady baseline or usual level of a disease

Define epidemic point source

cases that quickly increase but gradually decrease

Define epidemic propagating

cases with a steady and large increase

Out of the 4 epidemic plots which one would be want to LEAST likely see and Why?

epidemic propagating because it spreads continuously

Define Cumulative Incidence

measures the risk of healthy animals developing disease over time

How do we calculate Cumulative Incidence

new cases during that time period ÷ all non-sick animals at risk in the beginning

Define Incidence Density

how quickly new cases occur

how do we calculate Incidence Density

new cases ÷ total animal-time at risk

Define Case Fatality rate

how much death is there

How do we calculate Fatality Rate

death among all cases ÷ total number of cases

Define Outbreak

more cases of a disease than expected

What are 3 ways you can determine if something is a “true” outbreak

1. Calculating prevalence or incidence

2. Explore concurrent changes

   1. Evaluate economics

Why is it important to determine a “true” outbreak?

so that it can be addressed, handled and communicated properly

Define Relative Risk/ Risk Ratio

How many times greater is the risk of developing disease among those with the risk factor compared to those without

How is Relative Risk/ Risk Ratio calculated

the risk of new disease in those with the risk factor ÷ the risk of new disease in those without it

Define Relative Difference

How many extra new cases of disease occur among those with the risk factor compared to those without

How is Relative Difference calculated

the risk of new disease in those WITH the risk factor - the risk of new disease in those WITHOUT the risk factor

Define Prevalence Risk/Ratio

among those with the risk factor, what is the possibility of disease in those with the risk factor versus those without the risk factor

How is Prevalence Risk/Ratio calculated

current disease in the risk-factor group ÷ current disease in the no-risk-factor group

Define P Value

asking is the difference likely due to chance

What numbers would suspect that a factor is statistically significant

below 0.001 or 0.005

What numbers would suspect that it is likely due to random variation or chance

above 0.001 or 0.005

Define Confidence Interval

how certain we are that our estiamted value is close to the real value

Define Attributable Fraction

What proportion of new cases is due to the risk factor?

How is Attributable Fraction calculated

those infected w/ risk MINUS (-) those infected w/o risk

We can imporve health by…

1. preventing diseases

2. find diseases early

3. reduce diseases complications

What are the level of prevention and their definiton

1. Primary prevention: The disease has not started yet and prevented from occurring.

2. Secondary prevention: The disease may have started, but it is detected early

   1. Tertiary: The disease already causing complications but we reduce those complications

List the 10 steps in investigating a diseases outbreak

1. Establish that an outbreak exists.

2. Determine the key questions.

3. Define the cases and noncases.

4. Find all cases and relevant noncases.

5. Collect data on epidemiologic factors.

6. Look for patterns and trends.

7. Look for associations between factors and disease.

8. Form and test hypotheses.

9. Plan and implement control methods.

10. Communicate.

What can we consider the “key questions”

who, what, when,where, how, how much, why, etc.

What is considered a case vs a non case?

case is those with the outcome while a noncase is those without the outcome