# Shared Flashcard Set

## Details

Epidemiology
Basics of epi
14
Veterinary Medicine
10/21/2013

Term
 Define incidence
Definition
 Incidence is the frequency of an event occuring over a set period of time
Term
 Define prevalence
Definition
 The number of cases of a disease at any ONE TIME.P for prevalence, P for photo. It's a snapshot look at things
Term
 Define incidence risk
Definition
 Proportion of disease free animals developing disease during a specific time period. (Assumes closed population)
Term
 Animals 'at risk' are ones that
Definition
 - Can get the disease- Can be diagnosed as having the disease
Term
 Define incidence rate
Definition
 Number of new cases over a period of time________________________________________Accumulated sum of all individual's time at riskOR, for large populations:Cases ________________________________________________(start – ½ diseased – ½ withdrawn – ½ added) x time
Term
 What is the difference between incidence rate and risk?
Definition
 Both use the number of new cases occurring over time amongst an initially disease free population. The incidence rate has time as a denominator, while risk has the number of 'at risk' animals at the beginning of the study as a denominator.I.rate measures the rapidity of which new cases develop, while I.risk measures the risk of disease developing over time.
Term
 Is prevalence or incidence a better measure for a rare disease?
Definition
 Incidence is better because prevalence may not capture the disease in its 'snapshot' if the disease is very rare
Term
 Describe the difference in incidence and prevalence of a long term (chronic) disease
Definition
 Population incidence will be lower, though the prevalence will be higher.For example, the prevalence of chronic disease in a general population is growing because of both the higher incidence of chronic diseases (there are more cases each year than in the past) and the longer survival of patients with chronic disease resulting from modern treatments. If death rates drop, then the time that patients live with chronic disease grows and even a low incidence will produce a high prevalence.
Term
 What is a component cause?
Definition
 A contributing factor to disease (e.g. smoking for lung cancer or high cholesterol for heart disease)
Term
 What is a sufficient cause?
Definition
 The combination of conditions/causes without any one of which the disease would not have occurred.E.g. Respiratory disease in calves • Pasteurella spp., respiratory syncitial virus, stress • Disease occurs when two or more of these occur – Sufficient causes
Term
 What is a necessary cause?
Definition
 The most important piece of the pie - must be present for disease to occur • Example: Foodborne disease outbreak • Sufficient causes: Chicken salad and cream desert • Necessary cause: Salmonella spp
Term
 How do you calculate the risk ratio for a disease?
Definition
 Ratio of incidence risk in exposed group to incidence risk in unexposed group
Term
 How do you interpret a risk ratio?
Definition
 <1 = protective1 = no association> 1 = increased risk
Term
 What is an Odds ratio?
Definition
 Let p = the probability of an event 1-p = the probability that the event does not occur Odds of the event = p/1-pOdds of disease in exposed group divided by odds of disease in unexposed group
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