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56 Cards in this Set

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An organism that harbors a virus or parasite, typically providing nourishment & shelter.

Example: Cell (Virus), Animal (Parasitic Worm)
Anything Capable of harbouring/housing a diseases.
An organism that DOES NOT cause a disease itself, but spreads infection by conveying pathogens from one host to another

Example: Mosquito (Malaria), Flea (Bubonic Plague), Tick (Lyme Disease)
A living carrier that TRANSPORTS a disease
Models of Disease Transmission: Direct
Person to Person
Models of Disease Transmission: Indirect
(1) Common Vehicle: Single, Multiple, or Continuous exposure

(2) Vector
Single-Exposure, Common Vehicle Outbreak
1. Sudden, Rapid Increase in cases of Diseases

2. Few Secondary Cases

3. Log Transformation of a graph will show a bell shaped curve--Normal Distribution
A person or animal that harbors a specific infectious agent in the absence of a discernable clinical disease and serves a potential source of infection.

This Induvidual MAY infect others!! (i.e--Typhoid Mary)
Herd Immunity
If a large percentage of the population is immune, the entire population is likely to be protected for some person-to-person communicable diseases.
Habitual presence of a disease within a given geographic area
The occurance in a community or region of a group of illness of similar anture, CLEARLY IN EXCESS OF NORMAL EXPECTANCY, and derived from a common or from a propagated source
Explosive. Sudden rapid increase in number of cases of disease.
A worldwide epidemic
Incubation Period
The interval between invasion by an infectious agent and apperance of the first sign or symptom of disease.
Importance of the Incubation Period
1. Infected persons could be able to transmit the diease (even if not showing any signs or symptoms)

2. Quarantine: Isolate induviduals to prevent spread/transmission

3. Determine the length of quarantine.
Attack Rate
# of People at risk (in whom a certain illness develops) / Total # of people at Risk
Food-Specific Attack Rate
# of people who ate a certain food and became ill / Total # of people who that that food
Primary Case
A person who acquires the disease from exposure (i.e- from contaminated food)
Secondary Case
A person who acquires the disease from a primary case
Secondary Attack Rate
The attack rate in susceptible people who have been exposed to a primary case
Incidence Rate
The number of NEW cases of a disease that occur in a population during a specified period of time in a population at risk for developing the disease

(Case Diagnosed previously are NOT included in the numerator or denominator)
# of New Cases of Disease / # of people at risk of developing the disease
Cumulative Incidence
The porportion of a group of people who experience the onset of a health related event during a specified time interval.
i.e- Age Specific & Cause Specific

"Have your Ever had asthma!?" (Birth to Date)
The number of events in a given population at a designated time;
# of Cases of a disease / # of persons in the population at risk

Point Prevalance
The prevalence at the moment we measure it
i.e- "Do you have Asthma"
Period Prevalance
How many poeple have had the disease at any time during a certain period.
i.e- During a single calander year

i.e- "Have you had Asthma in the last year!?"
The unit combining time and population size. (If we compare 2 incidence rates in the same number of person-years, we would be able to compare how strong the force is that caused the disease)
Number of Persons x Observed Years
Relationship between Incidence & Prevalence
Prevalence = Incidence X Duration
Determinants of Prevalence
Incidence --->

Pool of Prevalence Cases-->

Passive Surveillance
Denotes surveillance in which either available data on reportable diseases are used, or reporting is mandated or requested with the responsibility for the reporting often falling on the health care provider or health officer
Active Surveillance
Denotes a system in which project staff make periodic field visits to health care facilities to collect data; Most of which is through Surveys
A fundamental role of Public Health. It may be carried out through monitoring changes in disease frequency or to monitor changes in prevalence risk factors
Case-Specific Mortality Rate
# of Deaths from this cause in one year / # of persons at risk in the population in the midyear
Cause-Fatality Rate (Percent)
# of dying persons during a specific period of time after disease onsent or Diagnosis / # of induviduals with this disease
Porportionate Mortality
# of deaths from a diseae in a population during a period of time / Total number of deaths from all causes in this population
YPLL (Years of Potential Life Loss)
The statistical measure of premature death and years of potential life lost compared to a target age (65 or 70)
Find the Average Age group & Subtract it from 65. Then Multiple the Average Age X The Number of Deaths = YPLL
Age-Adjusted Rate (Equation)
Sum of [Age-Specific Rate * WT]
Weighted Average
In order to calculate WT, we take the population of the subgroup (Age Group) and Divide it by the Total population.

This will give us the weighted average that the particular group has within the total population
SMR (Standardized Mortality Ratio)
(Observed # of Deaths / Expected # of Deaths) X 100
Expected Number of Deaths

SUM of [Age-Specfic Death Rate X WT from Standard Population]

DIRECT METHOD: use the rate in the population you are watching
Answer!? Compare to 100. (i.e-- If answer is 240, that means the risk of getting the particular disease is 140% higher in this population than in the general public OR if the answer is 75, than the risk in this population is 25% lower than the gen pop.)
Expected Number of Deaths

SUM of [Age-Specfic Death Rate X Number of Induviduals in the age group]

INDIRECT METHOD: use the rate in a standard population X # of the population you are watching now)
To confirm wheter someone has the disease
To find someone among asymptomatic people for further test. (This allows for early detection and treatment)
Test for all the people who TRULY DO have the diease

TP / (TP+FN)
Test for all of the people who truly DO NOT have the disease

TN / (FP + TN)
PPV (Positive Predictive Value)
People (+) for diease & Test (+)

TP / (TP + FP)
NPV (Negative Predictive Value)
People without (-) for disease & Test Negative

TN / (TN +FN)
Senstitivity vs. Specificity
If you increase one, it will cause a decrease in the other.
Sensitivity & Specificity measure QUALITY!! (not quantity)
Type I Error (Alpha Error)
People who DO NOT have the disase, but test (+)

"Queen Latifah"
FP / (FP + TN)
Type II Error (Beta Error)
People who HAVE the disease, but test (-)
FN / (TP + FN)
Gold Standard
A method or procedure or measurement that is widely accepted as being the best available or the "reference standard"
(TP + FN) / (TP + FP + TN + FN)
7 Principle for Screening Tests
1. Important
2. Effective Therapy exists
3. Risk of Screening Low
4. Test has High levels of Sensitivity & Specificity
5. Test must be acceptable to the population
6. Disease must be Common
7. Test is Low Cost
High Risk Population
In order to efficient, Screening is normally carried out in High Risk Populations (Due to an Increased PPV)
i.e-- High Risk Population for Breast Cancer= Women over the age of 50 (as apposed to Males or Younger Women)
The study of how disease is distributed in populations and the factors that influence or determine this distribution
Cause of Disease
Primary Prevention
Preventing the INITIAL DEVELOPMENT of a disease

Immunization, reducing Exposure to a Risk factor
Secondary Prevention
Early Detection of EXISTING DISEASE to reduce severity and complications

Screening for Cancer (Mammogram, Pap Smear)
Tertiary Prevention
Rehabiliation for Stroke