# Lec 2-4. Descriptive Epi & measures of disease frequency Flashcards

Define case definitions

a set of uniform criteria used to define a disease/condition for public health surveillance

What is the most critical element that must be defined before any of the ‘Who’ of descriptive epi can be acquired?

Case definition.

What does a cluster mean?

Occurrence of disease in a very small population. Smaller than outbreak.

Define Endemic

location that already has a higher than normal frequency of disease but that is their baseline.

Define epidemic

Occurrence of disease clearly in excess of normal. Population is bigger than outbreak.

What is the NNDSS?

CDC’s National Notifiable Diseases Surveillance System

What is the Incubation period?

Time between exposure & onset of disease. Basically pt exposed and disease process starts. Doesn’t know if pt feels it or not.

What is the Induction period?

Time between exposure & onset of disease. Basically pt exposed and disease process starts. Doesn’t know if pt feels it or not.

What is the Latency period?

Time between onset & disease detection. Basically how long does it take for someone to find it out.

Define Outbreak

Epidemic limited to a localized increase in occurrence of disease. Bigger than cluster, smaller than epidemic.

Define Pandemic

Epidemic spread world-wide.

Define epidemic curve

Graphical representation incorporating all 3 elements of descriptive epi. Person place time.

What things do epidemic curves visually demonstrate?

Magnitude & timing, and pattern of disease occurrence.

what does Magnitude and timing of disease occurrence mean pertaining to an epi curve?

Magnitude: numerical, we can see numbers. The bar gets taller more cases are being counted. Time: hours, days, months on the speed or aggressiveness of an illness.

Define a sentinel or index case

The first case.

What are two sub categories of Pattern of disease pertaining to an epi curve.

Common/point source (continuous & intermittent) and propagated source.

Define common/ point source (continuous & intermittent)

Not person-to-person spread, by a point source.

Define propagated source

person-to-person spread

What three hypotheses can the epi curve form?

Routes of transmission, probable exposure period, and incubation period.

Why can a disease be categorized as intermittent?

Disease is short lived

What are the 3 basic types of relative measures of disease frequencies?

Proportions, ratios and rates

Define proportions

Simple percentage, part over whole. Division of 2 RELATED numbers. Numerator is a subset of the denominator.

Define ratios

Division of 2 unrelated numbers. Numerator is not part of the denominator.

Define rates

A proportion (%) with TIME incorporated into the denominator.

What are 3 key factors in comparing measures of Disease frequency BETWEEN groups

How many people affected, size of the source population population, and the length of time following that population for that disease to occur.

What do you do when the size of the source population and length of time the population is followed are not the same between populations?

Standardize

What two terms describe disease frequency?

Incidence and prevalence