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Microbiology > Chapter 59: Principles of Epidemiology > Flashcards

Chapter 59: Principles of Epidemiology Flashcards

1
Q

what is epidemiology

A

science that evaluates occurrence, determinants, distribution and control of health and disease in a defined human population

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2
Q

what is sporadic disease and give example

A
  • occurs occasionally and at irregular intervals
  • histoplasmosis
  • gas gangrene
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3
Q

what is endemic disease and give examples

A
  • maintains a relatively steady low level frequency at a moderately regular interval
  • gonorrhea
  • dengue fever
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4
Q

what is holoendemic diseases and what is an example

A
  • occurs at a high, constant level throughout a population
  • malaria
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5
Q

what is epidemic and give exmaple

A
  • sudden increase in frequency above expected number
  • influenza and meningococcal infection
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6
Q

what is the first case in an epidemic called

A

index case

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7
Q

what is an outbreak

A

sudden unexpected occurrence of disease
- usually focal or in a limited segment of population

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8
Q

what is a pandemic

A

increase in disease occurrence within large population over wide region

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9
Q

what is morbidity rate

A
  • an incidence rate
  • number of new cases in a specific time period per unit of population
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10
Q

what is prevalance rate

A
  • total number of individuals infected at any one time per unit of population
  • depends both on incidence rate and duration of illness
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11
Q

what is mortality rate

A

number of deaths from a disease per number of cases of the disease

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12
Q

what is R0 or R naught

A

number of secondary cases one case would produce in a completely susceptible population

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13
Q

R(0) calculated as a function of 3 primary parameters

A
  • duration of contagiousness after a person becomes infection
  • likelihood of infection per contact between a susceptible person and an infectious person or vector
  • contact rate
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14
Q

what does infectious disease epidemioogy try to determine

A
  • causative agent
  • source and/or resevoir of disease agent
  • mechanism of transmission
  • host and environmental factors that facilitate development of disease within a defined population
  • best control measures
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15
Q

what are signs

A

objective changes in body that can be directly observed

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16
Q

what are symptoms

A

subjective changes experienced by patient

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17
Q

what is the course of infectious disease

A

-incubation period
- prodromal stage
- period of illness
- convalescence

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18
Q

what is the incubation period

A

period after pathogen entry but before signs and symptoms appear

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19
Q

what is prodromal stage

A

onset of signs and symptoms
- not clear enough for diagnosis

20
Q

what is period of illness

A

disease is most severe and has characterisitc signs and symptoms

21
Q

what is convalescence

A

signs and symptoms begin to disappear

22
Q

what are the 2 types of epidemics

A

common source epidemics and propagated epidemic

23
Q

what is threshold density

A

minimum number of individuals necessary to continue propagating the disease

24
Q

what is herd immunity

A

resistance of a population to infection and to spread of an infectious organism because of the immunity of a large percentage of the population

25
Q

what is antigenic shift

A

major change in antigenic character of pathogen

26
Q

what is antigenic drift

A

smaller antigenic changes

27
Q

what is a source

A

location from which the pathogen is transmitted to the host

28
Q

what is period of infectivity

A

time during which source is infectious or disseminating the organism

29
Q

what is a reservoir

A

site or natural environmental location in which pathogen in normally found
- can function as source of pathogen

30
Q

what is an active carrier

A

has overt clinical case of disease

31
Q

what is convalescent carrier

A

has recovered from disease but continues to harbor large numbers of pathogen

32
Q

what is a healthy carrier

A

harbors pathogen but is not ill

33
Q

what is an incubatory carrier

A

harbors pathogen but it not YET ill

34
Q

describe animal reservoirs

A
  • numerous diseases are zoonosed
  • ## transmission to human can be direct or indirect
35
Q

what are vectors

A

organisms that spread disease from one host to another

36
Q

what are the types of airborne transmission

A
  • pathogen suspended in air and travels more than 1 meter
  • droplet nuclei
  • dust particles
37
Q

describe droplet nuclei

A

small particles
- can remain airborne for llong time
- can travel long distances
- usually propelled from respiratory tract of source organisms by sneezing, coughing or vocalization

38
Q

what is contact transmission

A
  • coming together or touching of source/ reservoir and host
  • direct contact
  • droplet spread
39
Q

what are vehicles of transmission

A

inanimate materials or objects involved in pathogen transmission

40
Q

what is external vector borne transmission

A

passive carriage of pathogen on body of vector
- no growth of pathogen during transmission

41
Q

what is internal transmission of vectors

A
  • carried within vector
  • harborage transmission - pathogen does not undergo changes within vectro
  • biologic trnasmission- pathogen undergoes changes within vector
42
Q

why is a host susceptible to a pathogen

A
  • defense mechanisms of the host
  • pathogenicity of pathogen
43
Q

how does a pathogen leave the host

A
  • active escape: movement of pathogen to portal of exit
  • passive escape: excretion in feces, urine, droplets, saliva or desquaminated cells
44
Q

how are epidemics controlled

A
  • reduce or eliminate source of reservoir
  • break connection between source and susceptible individuals
  • reduce number of susceptible individuals
45
Q

how are reservoirs reduced or eliminated

A
  • quarantine and isolation of cases and carriers
  • destruction of animal reservoir
  • treatment of sewage
  • therapy that reduced or eliminates infectivity of cases
46
Q

how is connection between source and susceptible individuals broken

A
  • chlorination of water supplies
  • pasteruization of milk
  • supervision and insepction of food and food handlers
  • destruction of insect vectors with pesticides
47
Q

how is the number of susceptible individuals reduced

A
  • passive immunity following exposure
  • active immunity for protection
  • herd immunity

Microbiology (39 decks)

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