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UVic BIOL 459 amy > MT2 > Basic Concepts in Epidemiology > Flashcards

MT2 > Basic Concepts in Epidemiology Flashcards

1
Q

What definition describes the “incidence” of a disease?

A

The rate of development of a disease in a group over a period of time.

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2
Q

What definition describes the “prevalence” of a disease?

A

The number of people who have the disease at a certain point in time.

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3
Q

What is an example which uses the term “incidence” in relation to disease?

A

The incidence of myocardial infarction is about 1% per year in men aged 55-59 in our community.

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4
Q

What is an example which uses the term “prevalence” in relation to disease?

A

The presence of diarrhea in the children’s camp on July 13th was 33%.

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5
Q

What scale is used when talking about prevalence rates? What about incidence rates?

A

Prevalence: rates per 10,000
Incidence: rates per 100,000

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6
Q

For which 3 important notifiable diseases is the incidence rate higher in BC than the Canadian average?

A
  1. AIDS
  2. Hepatitis C
  3. Pertussis
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7
Q

For which 2 important notifiable diseases is the incidence rate lower in BC than the Canadian average?

A
  1. Gonococcal infections

2. Verotoxigenic E. coli

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8
Q

What definition describes the “morbidity” of a disease? Does it refer to prevalence or incidence?

A

The incidence of illness (disease) in a population. Includes both fatal and nonfatal at a point in time. Can refer to either prevalence or incidence.

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9
Q

What is an example which uses the term “morbidity” in relation to disease?

A

Morbidity rate of genital Chlamydia in Canada in 2000 was 32%.

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10
Q

What definition describes the “mortality” of a disease?

A

The incidence of death in a population.

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11
Q

What is an example which uses the term “mortality” in relation to disease?

A

The mortality rate varied from 25% to 33% of Europe’s population during plague epidemics in the middle ages.

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12
Q

What is meant by the term “Case Fatality Rate”?

A

An estimate of the number of deaths due to a disease based on the mortality rate of a small sample.

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13
Q

What is meant by a “sporadic” disease?

A

A disease which occurs only occasionally.

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14
Q

What is meant by a “endemic” disease?

A

A disease which is constantly present in a population.

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15
Q

What is meant by a “epidemic” disease?

A

A disease which is acquired by many people in a given area in a short time.

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16
Q

What is meant by a “pandemic” disease?

A

A worldwide epidemic.

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17
Q

What is meant by an “acute” disease?

A

A disease in which symptoms develop rapidly but the disease lasts only a short time.

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18
Q

What is meant by a “chronic” disease?

A

A disease in which symptoms develop slowly.

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19
Q

What is meant by a “subacute” disease?

A

A disease in which the severity is intermediate between acute and chronic.

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20
Q

What is meant by a “latent” disease?

A

A disease in which the causative agent is inactive for a time but then activates and produces symptoms.

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21
Q

What is meant by “herd immunity”?

A

Immunity in most of the population can prevent those with out immunity by limiting transmission of a disease.

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22
Q

What is meant by a “local” infection?

A

An infection in which the pathogen is limited to a small area of the body.

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23
Q

What is meant by a “systemic” (or “generalized”) infection?

A

An infection in which the pathogen has spread to the entire body.

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24
Q

What is meant by a “focal” infection?

A

A systemic infection which began as a local infection.

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25
Q

Define sepsis.

A

A toxic inflammatory condition arising from the spread of microbes from a focus of infection.

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26
Q

Define bacteremia.

A

Bacteria in the blood.

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27
Q

Define septicemia.

A

Aka: blood poisoning. The growth of bacteria in the blood.

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28
Q

Define toxemia.

A

Toxins in the blood.

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29
Q

Define viremia.

A

Viruses in the blood.

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30
Q

Define a primary infection.

A

An acute infection which causes the initial illness.

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31
Q

Define a secondary infection.

A

An opportunistic infection which follows a primary infection.

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32
Q

Define a subclinical disease.

A

An infection which produces no noticeable signs or symptoms.

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33
Q

List some predisposing factor which can in some cases make the body more susceptible to disease.

A
  • Gender
  • Inherited traits (ex: anemia)
  • Climate and weather
  • Fatigue
  • Age
  • Lifestyle
  • Nutrition
  • Chemotherapy
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34
Q

Describe the “incubation period” of a disease.

A

The interval between the initial infection and the first signs and symptoms.

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35
Q

Describe the “prodromal period” of a disease.

A

The short period after incubation in which the patient presents with early, mild symptoms.

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36
Q

Describe the “period of illness” of a disease.

A

The period during a disease’s progression in which the symptoms are most severe.

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37
Q

Describe the “period of decline” of a disease.

A

The period after maximum severity in which signs and symptoms subside.

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38
Q

Describe the “period of convalescence” of a disease.

A

The period at the very end of disease progression in which the body returns to its prediseased state.

39
Q

What are the 3 main continual sources of infection?

A
  1. Human reservoirs (carriers)
  2. Animal reservoirs (zoonoses)
  3. Nonliving reservoirs
40
Q

What term in used to describe a nonliving object capable of spreading disease via indirect contact transmission? Give an example.

A

A fomite. Objects which can harbour infection such as surgical devices, clothes, furniture, etc.

41
Q

As per the definition, what is the distance cutoff for disease spread via droplet transmission?

A

<1 meter.

42
Q

In what 3 ways can disease be transmitted via an inanimate reservoir?

A
  1. Waterborne
  2. Foodborne
  3. Airborne (dust, etc)
43
Q

With regard to disease vectors, what differentiates mechanical transmission from biological transmission?

A

Mechanical: vector carries pathogen on its feet
Biological: pathogen reproduces in the vector and is transmitted vie bites or feces

44
Q

What is another term used to describe a healthcare-associated infection? How many hospital patients are infected per year?

A

A nosocomial infection, which infects ~2 million patients per year (1 in 25). (~20,000 deaths).

45
Q

What 3 factors play the greatest role in perpetuating healthcare-associated infections?

A
  1. Microorganisms in the hospital environment
  2. Weakened status of the host
  3. Chain of transmission in a hospital
46
Q

What 3 factors most commonly compromise a person’s immunity in a hospital setting?

A
  1. Ongoing disease
  2. Therapy
  3. Burns
47
Q

Describe an “emerging infectious disease”.

A

A disease which is new and either increasing in incidence or showing the potential to increase in incidence soon.

48
Q

What are 3 common characteristics of emerging infectious diseases?

A

Most are:

  1. Zoonotic
  2. Viral in origin
  3. Vector-borne
49
Q

What 8 main factors contribute to the emergence of new infectious diseases.

A
  1. Genetic recombination
  2. Evolution of new strains
  3. Antibiotic/pesticide use
  4. Changing weather patterns
  5. Modern transportation
  6. Ecological disaster/war/human expansion
  7. Animal control measures
  8. Public health failure
50
Q

What is an example of a virus whose spread is affected by changing weather patterns? How?

A

Hantavirus is spread by deer mice, which are expanding their range because of climate change.

51
Q

What is the definition of “epidemiology”?

A

The study of where and when diseases occur and how they are transmitted in populations.

52
Q

What is the definition of “etiology”?

A

The cause, set of causes, or manner of causation of a disease.

53
Q

What was epidemiologist John Snow known for doing in 1848-1849?

A

He mapped the occurrence of cholera in London.

54
Q

What was epidemiologist Ignaz Semmelweis known for doing in 1846-1848?

A

Showed that handwashing decreased the incidence of pleural sepsis.

55
Q

What was epidemiologist Florence Nightingale known for doing in 1858?

A

Showed that improved sanitation decreased the incidence of epidemic typhus.

56
Q

What definition best describes “descriptive” epidemiology? Which known epidemiologist best embodies this approach?

A

The collection and analysis of data pertaining to a disease. John Snow.

57
Q

What definition best describes “analytical” epidemiology? Which known epidemiologist best embodies this approach?

A

The analysis of a particular disease to determine its probable cause. Florence Nightingale.

58
Q

What definition best describes “experimental” epidemiology? Which known epidemiologist best embodies this approach?

A

Involves a hypothesis and controlled experiments pertaining to a disease. Ignaz Semmelweis.

59
Q

What organization publishes the “Morbidity and Mortality Weekly Report” (MMWR)?

A

The Centers for Disease Control and Prevention (CDC).

60
Q

What is a notifiable infectious disease?

A

A disease which physicians are required to report if they see an occurrence.

61
Q

What are some examples of well known notifiable diseases?

A

Any of:
AIDS, Chickenpox, Chlamydia, Cholera, Syphilis, Diptheria, Gonorrhea, Influenza, Hantavirus, Hepatitis A/B/C, HIV, Leprosy, Lyme disease, Malaria, Measles, Mumps, Plague, Rubella, etc.

62
Q

When did Mycobacterium tuberculosis get put on the notifiable disease list? Is there a vaccine? How is it treated?

A
  1. There is a vaccine but it is unreliable. Treated with antibiotics (compliance very important).
63
Q

What populations are at increased risk of contracting tuberculosis? Why?

A

First Nations and some African populations have a mutation in the NRAMP1 gene which increases susceptibility.

64
Q

Who can initiate an outbreak investigation?

A

Clinicians, patients, Healthcare agencies with surveillance data, News agencies.

65
Q

What 4 basic strain-typing techniques are used in molecular biology?

A
  1. PCR
  2. Hybridization
  3. Cloning
  4. Sequencing
66
Q

What is “strain-typing” in epidemiology?

A

Molecular analysis of a disease to determine the strain.

67
Q

What 3 main components are required for PCR?

A
  1. Primers
  2. Target DNA
  3. taq polymerase
68
Q

What do each of Southern, Northern, and Western blotting techniques isolate?

A

Southern Blot: DNA
Northern Blot: RNA
Western Blot: Proteins

69
Q

In what orientation are DNA sequences submitted for cataloguing?

A

Always 5’-3’.

70
Q

When selecting a strain-typing method, why is it important to consider typeablility?

A

We want the test to generate an unambiguous result for whatever isolate we test.

71
Q

When selecting a strain-typing method, why is it important to consider reproducibility?

A

We want the test to produce consistent identical responses for a given strain.

72
Q

When selecting a strain-typing method, why is it important to consider stability?

A

We want to identify a character for molecular typing which is not subject to rapid evolution or lost by host.

73
Q

When selecting a strain-typing method, why is it important to consider epidemiologic concordance?

A

Our method of molecular typing has to effectively group outbreak-related strains.

74
Q

When selecting a strain-typing method, why is it important to consider typing system concordance?

A

Our method of molecular typing has to compare favourably with a previously validated test.

75
Q

What 4 main methods are used for phenotypic strain typing?

A

Typing by:

  1. Growth and morphology
  2. Biochemical characteristics
  3. Function or physiology
  4. Serologic characteristics
76
Q

What are some examples of techniques for phenotypic strain-typing using growth and morphologic characteristics?

A
  • Gram staining
  • Acid fast staining
  • Growth on agar plates
77
Q

What is an example of a technique used for phenotypic strain-typing using biochemical characteristics?

A

By targeting lactose fermentation we can detect Lactose-fermenting E. coli in the GI tract.

78
Q

What are some examples of techniques for phenotypic strain-typing using functional or physiological characteristics?

A
  • Toxigenicity bioassays
  • Survival characteristics
  • Multilocus enzyme electrophoresis
  • Antimicrobial susceptibility
  • Phage typing
  • Cell culture assays
79
Q

What is an example of a technique used for phenotypic strain-typing using biochemical characteristics?

A

Differentiation based on antigenic determinants. We identify inlfuenza strains based on H and N antigenic proteins.

80
Q

What is a bacteriocin?

A

A short peptide that inhibits other bacteria.

81
Q

What is ELISA? How can it be used for strain-typing?

A

Enzyme Linked Immuno-Sorbent Assay can identify antibodies to viruses that are present in the sample.

82
Q

What 5 steps outline strain-typing by Western (Immuno-) Blot?

A
  1. Denature. Separate by electrophoresis
  2. Blot from gel to membrane
  3. Treat membrane w/ specific antibodies
  4. Add antigen-antibody complex markers
  5. Expose to film or substrate to reveal protein
83
Q

What 3 main methods are used for genotypic strain-typing?

A
  1. Nucleic acid extraction
  2. Analysis of extrachromosomal DNA elements
  3. Genome-based typing methods
84
Q

What are the 5 genome-based strain-typing methods mentioned in class?

A
  1. Restriction endonuclease analysis
  2. Southern Blot hybridization
  3. Pulse-Field Gel Electrophoresis (PFGE)
  4. Whole genome sequence comparison
  5. Microarray comparisons
85
Q

During a restriction endonuclease analysis, what are some example of “rare cutters” which are required for genome analysis?

A

Not1, EcoR1, EcoR5.

86
Q

Describe Pulse-Field Gel Electrophesis (PFGE). Why would we use this?

A

Like normal electrophoresis, but the angle of the electric field alternates by 120 degrees every 90 seconds for 18-24 hours. Used when the fragments would be too large for normal electrophoresis.

87
Q

Do pathogenic bacteria tend towards smaller or larger genomes? Why?

A

Smaller genomes to streamline the replication process and increase pathogenicity.

88
Q

What can PCR target?

A

A coding region (gene) or a non-coding region (repetitive element).

89
Q

How can PCR be used to monitor CD4 and determine disease prognosis?

A

PCr can tell us whether the quantity of CD4 is keeping up with the infection (good) or beginning to drop off (bad).

90
Q

What is spoligotyping?

A

Spacer oligonucleotide typing. A rapid PCR-based method for strain-typing

91
Q

How would you calculate the incidence rate of a disease?

A

(# of people to develop a disease / total # of people all risk) * unit time

92
Q

How would you calculate the prevalence of a disease?

A

(# of people with a disease / total # of people in group)

93
Q

How would you calculate the mortality rate of a disease?

A

(# of people dead from a disease / total # of people in group) * unit time

UVic BIOL 459 amy (16 decks)

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