Term
|
Definition
-living organism or inanimate matter (such as soil) in which infectious agents normally live and multiply
-humans, animals, and environmental sources |
|
|
Term
|
Definition
vertebrate animals that are the usual resevior of infection
-can transmit to humans: i.e. rabies, anthrax, etc |
|
|
Term
| Colonization (of Infection) |
|
Definition
-first stage
-the ability to get to a host and survive enought to multiply |
|
|
Term
| Inapparent Infection (of Infection) |
|
Definition
-second stage
-not only multiply, but cause a measurable, sub-clinical reaction |
|
|
Term
| Overt Disease (of Infection) |
|
Definition
-third stage
-above clinical horizon, clinically apparent disease |
|
|
Term
|
Definition
-an infected person without clinically apparent disease
-potential source of infection to others
-may remain inapparent or follow manifest disease |
|
|
Term
| Incubatory Carrier (1 of 3) |
|
Definition
-before apparent infection
ex: chicken pox |
|
|
Term
| COnvalescent Carrier (2 of 3) |
|
Definition
-spread of disease while infected
ex: diptheria |
|
|
Term
|
Definition
-disease stays with you, spread when well
ex: hepititis B |
|
|
Term
| Direct Trasmission of Disease |
|
Definition
-immediate transfer of infected cells from from infected host or resevior
ex: sneezing, kissing, contact with soil or vegetation |
|
|
Term
Indirect Transmission of Disease:
Vehicle Bourne |
|
Definition
-conveyed through an inanimate object
ex: fomites, bedding, surgical instruments, food, IV fluid |
|
|
Term
Indirect Transmission of Disease:
Vector Bourne |
|
Definition
-conveyed by arthropod to host
-may carry mechanically (on body)
-may be part of complex biological cycle in arthropod |
|
|
Term
Indirect Transmission of Disease:
Air Bourne |
|
Definition
-dusts: particles of varying size that result from resuspension
-droplet nuclei: tiny particles formed by evaporation of materials that have been coughed or sneezed |
|
|
Term
|
Definition
-outbreaks due to exposure of a group to a common source
-when exposure is brief and initially simultaneous, resultant cases develop within one incubation period
ex: chemical agents or poisons like pollution |
|
|
Term
| Propogated/Progressive Epidemic |
|
Definition
-direct or indirect transmission from one susceptible host to another of infectious agent
-upward trend at onset, increase of number of cases in each successive time period |
|
|
Term
| Temporal Trends in Common Source and Propogated Epidemics |
|
Definition
Common Source: rapid rise and fall in one incubation period
Propogated: new cases develop outside 1 incubation period |
|
|
Term
| Geographic (Spot Map) Distribution in Common Source and Propogated Epidemics |
|
Definition
| Propogated: radial spread with each succesive generation of cases |
|
|
Term
|
Definition
-the period between the receipt of infection by a host and maximum communicability of a disease
-roughly equals the incubation period, but terms are not the same (may precede or follow incubation period, but mostly precedes) |
|
|
Term
|
Definition
-term used to express the immunity of a group. resistance to invasion or spread of infectious agent
-important factor underlying the dynamic of propagated epidemic and periodicty of diseases (prior to vaccine use)
-not necessary to immunize 100% of the population to halt the spread of an epidemic |
|
|
Term
|
Definition
(number of new cases - initial cases)/(number susceptibles in a group - initial cases)
-measurement of a spread within a group (where an index case has already been identified) |
|
|
Term
| Control Measures Against Resevior |
|
Definition
-immunication or eradication
-isolation (separation of infected) or quarentine (not as extreme as isoloation, limitation of freedom of movement)
-survailence of individuals has replaced quarentines. Close supervision is maintained with possible contacts of ill persons |
|
|
Term
| Control Measures that Interrupt Transmission by Organisms |
|
Definition
| -environmental measures (purification of water, milk pasteuization, food inspections, ventilation systems, insecticide sprays) |
|
|
Term
| Control Measures that Reduce Host Susceptibility |
|
Definition
-immunization programs
-most are part of routine pediatric practice, but some are specific to occupation or travel) |
|
|
Term
|
Definition
-purpose is to monitor incidence or prevelance of disease behavior that is placing people at risk
-opperated by CDC: MMWRs
-52 infectious diseases currently on U.S. list, but changes periodically as new ones emerge |
|
|
Term
|
Definition
Ex 1: Small pox
-first attempt targeted at risk population
-second attempt emphasized survailence and containment
-declared eradicated in 1980
Ex 2: Polio
-more difficult than small pox due to large amount of sub-clinical infections
-eradicated from western hemisphere in 1991
-remaining reseviors in African nations and South Asia |
|
|
Term
| Outline of Investigation of an Epidemic |
|
Definition
-verify the diagnosis
-verify the existence of an epidemic
-describe the epidemic with respec to time, place, person
-formulat and test a hypothesis
-search for additional cases
-analyze the data
-report about hypothesis |
|
|
Term
|
Definition
-identify vital health facts in a given community, population, or area
-morbidity, mortality, life expectancy, birth and death rates, marriages, divorce, demographics, and census data |
|
|
Term
| Vital Events Registration |
|
Definition
| -birth certificates, marriage, divorce, death, and major notifiable diseases |
|
|
Term
|
Definition
-secondary prevention
-presymptomatic identificaion of yet unrecognized disease by testing, etc |
|
|
Term
| Normal (in Disease Screening) |
|
Definition
-typical: usual value of a population group characteristic
-functional: any value can be considered normal if there is no increased risk associated with it
-statistical: regerring to the normal of Gaussian distribution
-distribution with standard deviation (95% of pop within 2 standard deviation units)
-dichotimous classification is often too simplistic |
|
|
Term
| Screening Evaluation: Validity: Sensitivity |
|
Definition
-the abilito to correctly idenitify those who have the disease
percent sensitivity = TP/(TP + FN) |
|
|
Term
| Screening Evaluation: Validity: Specificity |
|
Definition
-ability to identify thosse who don't have the disease
percent specificity = (TN)/(TN + FP) |
|
|
Term
| Screening Evaluation: Tests in a Series |
|
Definition
-labeled positive if positive to all, negative if negative to any
-enhances specificity |
|
|
Term
| Screening Evaluation: Tests in Parallel |
|
Definition
-labeled positive if positive to any
-enhances sensitivity |
|
|
Term
| Screening Evaluation: Reliability |
|
Definition
-test that gives consistant results when performed more than once on the same individual under same conditions
-observer variation and variation inherent in the method can affect reliability |
|
|
Term
| Screening Evaluation: Yield |
|
Definition
-amount of previously unrecognized disease diagnosed and brought to treatment
-dependent on test sensitivity, prevelence of unrecognized disease, extent of previous screenings, health behavior |
|
|
Term
| Screening Evaluation: Predictive Value |
|
Definition
-most important property of a screening test
-ability of a test to predict the presence of absence of a disease
Positive predictive value = (TP)/(TP + FP)
Negative predictive value = (TN)/(TN + FN) |
|
|
Term
|
Definition
-start with a cohort all considered to be free of a given disease but vary in exposure to a possible etiologic factor
-cohort is followed over time to see who gets the disease |
|
|
Term
| analyzing prospective studies |
|
Definition
-calculate IR of those exposed and those not exposed, then calculate relative risk (RR)
RR = (IR exposed)/(IR not exposed)
RR = [A/(A + B)]/[C/(C + D)]
Disease Present Disease Absent
Exposed A B
Not Exposed C D |
|
|
Term
|
Definition
-peopled diagnosed as having some disease (CASES) compared with people who do not have the disease (CONTROLS)
-purpose: to determine if the two groups differ in proportion of persons exposed to a single/specific factor
-controls should resemble the cases closely, usually using matching |
|
|
Term
| analysis of retrospective study |
|
Definition
-true incidence cannot be calculated because there are not appropriate denominators (i.e. no population at risk)
-calculate the odds ratio:
OR = (A x D)/(C x B)
Case Control
Factor A B
No Factor C D |
|
|
Term
| Historical Prospective Study |
|
Definition
| -identify a cohort at some point in the past and analyze subsequent morbidity and mortality (use vital stats) |
|
|
