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Flashcards in Final Deck (159)
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1
Q

What is Tularemia

A

Bacteria, rabbits and rodents, ticks/deer fly/dust/etc, BIOTERROR. Ucler, fever, sore throat, diarrhea, pneumonia, etc. Incubation period 3 - 4 days

2
Q

Viruses

A

HIV, West Nile, Hanta, Rabies, Measles

3
Q

Bacteria

A

Lyme disease, Plague, Anthrax, TB, Tularemia.

4
Q

Fungi

A

Cave disease, Candida,

5
Q

Parasites

A

Malaria, Giardia, Nematodes, Guinea Worm

6
Q

Prions

A

Kuru, Bovine spongiform encephalitis, Chronic Wasting Disease, Fatal familial insomnia,

7
Q

Other than Viruses, bacteria, fungi, parasites, prions, what are other “disease agents”?

A

Cancers, Pollutants (Environmental/occupational), Socio-economic status (mental health, poverty, exposure)

8
Q

Modes of transmission?

A

Contact (direct/indirect), Respiratory, Airborne, Vehicle-borne, Vector Borne, Vertical transmission,

9
Q

Contact (direct/indirect)

A

via touch. (STD, Rhinovirus)

10
Q

Respiratory droplets/secretion

A

via cough/sneeze

11
Q

Airborne route

A

via Airborne (droplet nuclei, dust,) Eg. TB, measles, hantavirus

12
Q

Two forms of airborne falling droplets

A
  1. Large droplets fall to the ground (rain) Eg. Ebola 3 feet. 2. small drops float in the air (fog) Eg. Measles 6 ft.
13
Q

Vehicle-borne

A

Via ingestion, injection. (food, water, intra-venous injection). Eg Salmonella, norovirus, cholera, giardiasis, botulism, HIV hep B

14
Q

Vector-Borne

A

Either Mechanical and/or biological. Ticks, mosquitos, fleas, etc. Lyme disease, malaria, yellow fever, Chaga’s, plague, etc.

15
Q

Vertical transmission

A

From mother to offspring. Eg. Streptococcus, Toxoplasmosis, HIV, Hep B.

16
Q

What is the anatomy of disease?

A

“DREEMS” - Disease agent (What is it?), - Reservoir / source? - Entry into host - Exit from infected host - Mode of transmission - Symptoms

17
Q

Disease agent

A

virus, bacteria, fungi, prion, parasites.

18
Q

EIDS

A

Emerging Infectious Diseases

19
Q

Global trends of disease agents?

A

Yes. Trends vs outbreaks.

20
Q

What is a Reservoir

A

Reservoir hosts of an infectious disease serve as a source of infection and sustain the pathogen in a population.

21
Q

Index Case

A

The initial patient in the population sample of an epidemiological investigation. (Also: primary case or patient zero)

22
Q

SARS

A

Severe Acute Respiratory Syndrome

23
Q

Epidemic Curve

A

a graphic depiction of the number of outbreak cases by date of illness onset

24
Q

Epidemic curves provide information on:

A
  1. Disease incubation period 2. Outbreak magnitude 3. Time Trend 4. Pattern of disease spread
25
Q

Latent period

A

Between Infection and Infectious.

26
Q

Infectious period

A

From infectious to cure / pathogen death

27
Q

Incubation period

A

Between infection and onset of symptoms

28
Q

Symptomatic period

A

Between Onset of symptoms and non-diseased

29
Q

Early warning (infections)

A

symptoms precede infectiousness

30
Q

Lag warning

A

Symptoms follow infectiousness

31
Q

What is outbreak magnitude

A
  • How many people are infected? Magnitude in sub-populations
32
Q

What is a time trend? (epidemic curve)

A

Tells us if the disease is still spreading.

33
Q

What is it called when cases acquire the infection from the same source?

A

Common source

34
Q

Common source - point

A

Period of exposure is brief, and all cases occur within

35
Q

Common source - continuous

A

often causes epidemic curve to rise gradually

36
Q

Common source - intermittent

A

intermittent exposure often results in epidemic curve with irregular peaks, which reflect the timing and extent of the exposure

37
Q

Propagated outbreak

A

spread from person to person, long lasting, multiple waves of infection. Each peak is slightly taller than the previous one. Each peak separated by an incubation period.

38
Q

SARS movement

A
  1. Feb 2003, From Hong-Kong to Taipei 2. March 2003, Hong-Kong to Beijing
39
Q

Case fatality ratio

A

number of deaths / number of cases

40
Q

When can you declare disease free?

A

When two consecutive incubation periods pass without new cases.

41
Q

Zoonotic disease is…

A

an animal to human transmission

42
Q

Prevalence

A

= Number positive / number tested = number of positive samples / sample size

43
Q

Koch’s postulates?

A

Koch’s postulates to identifying disease agents. 1. The organism is always found with the disease 2. the organism is not found with any other disease 3. The organism, isolated from one who has the disease, and cultured through several generations, produces the disease (in experimental animals)

44
Q

Positive results mean what? (in testing for disease)

A
  1. Agent is present 2. Contamination 3. Random events
45
Q

Negative results mean what? (in testing for disease)

A
  1. Target is absent 2. Failure to work 3. Random events
46
Q

True positive is…

A

Positive results, has the disease

47
Q

False positive is…

A

Positive test, does not have the disease

48
Q

true negative

A

negative test, does not have the disease

49
Q

false negative

A

negative results, has the disease

50
Q

Test Validity

A

the ability to distinguish between presence and absence of a disease

51
Q

Sensitivity

A

ability of test to correctly identify cases that HAVE THE DISEASE - Practice calculating

52
Q

Specificity

A

ability of the test to correctly identify cases that DO NOT HAVE THE DISEASE - Practice calculating

53
Q

Sensitivity calculation

A

TP / (TP + FN)

54
Q

Specificity calculation

A

TN / (TN + FP)

55
Q

What influences test validity ?

A
  • Test Type - Sampling time of test - Prevalence of the disease (rare or common) - Number of times test is performed
56
Q

What is PPV

A

Positive predictive value

57
Q

How do you calculate PPV

A

TP / (TP + FP)

58
Q

What is NPV?

A

Negative predictive value

59
Q

How do you calculate NPV?

A

TN / (TN + FN)

60
Q

What is a cluster?

A

Observation of above normal number of cases

61
Q

Outbreak

A

Sudden increase in disease cases

62
Q

Epidemic

A

Outbreak on a large scale

63
Q

Pandemic

A

Outbreak at international/global scale

64
Q

Endemic

A

Normal, baseline, natural distribution/rates of disease

65
Q

Epizootic

A

epidemic for wildlife

66
Q

Enzootic

A

endemic for wildlife

67
Q

What do maps tell us?

A
  • Predict spread and allow instigation of control/preparations - The importance of local context & scale
68
Q

Anatomy of Lyme disease?

A

Agent: Bacterium Borrelia burgdorferi Transmission: Vector-Borne, ticks Reservoir/source: Small mammals

69
Q

Incidence

A

Number of new cases that occur during a specified period of time, in a population at risk for developing the disease

70
Q
  1. Case investigation steps
A
  1. Verify that an outbreak is occurring 2. Establish preliminary hypothesis 3. Make a case definition 4. Make case questionnaires 5. Organize data (line listing) 6. Describe current outbreak information
71
Q

Case definition means…

A

begin with a ‘loose’ case definition during initial outbreak. What is the disease? Who is a case? Who is not a case? Establish definition using disease symptoms, disease agent & stain, & likely route of exposure.

72
Q

What is a notifiable case of SARS is defined as….

A

an individual with laboratory confirmation of infection with SARS coronavirus (SARS-CoV)

73
Q

Suspected Case

A

A clinically compatible case without presumptive or confirmatory laboratory results

74
Q

Probable Case

A

A clinically compatible case with presumptive laboratory results

75
Q

Confirmed Case

A

A clinically compatible case with confirmatory laboratory results

76
Q

Contact Tracing

A

process of locating and notifying partners (contacts) that they have been exposed to a disease (AKA partner tracing). Syphilis, gonorrhoea, TB, measles, HIV (!!!)

77
Q

Line Listing

A

(organizing data) Common file for information

78
Q
  1. Cause investigation
A

systematically review possible reservoir/source & casual agents (anatomy of disease). Remember L.E.V.EL!!! L - laboratory investigations E - epidemiologic/clinical investigations V - Veterinary/wildlife/vector investigations E - Environmental investigations L - Law enforcement investigations

79
Q

Control measures

A
  1. Case investigation 2. Cause investigation 3. Control measures - ACT FAST
80
Q
  1. Conduct analytic study with…
A

RISK RATIOs

81
Q

Cohort

A

a well-defined group of subjects or patients who have had a common experience or exposure and are then followed up for the incidence of new diseases or events.

82
Q

Incidence =

A

number of new cases that occur during a specific period of time, in a population at risk for developing the disease

83
Q

Person-time units =

A

length of time individuals are in states of health, exposure (at risk), infection, infectiousness, etc. (or how many people and for how long??) – 10 people studied for 6 weeks. = 60 person-weeks

84
Q

Fixed cohort

A

all people present at beginning of study; no new entries

85
Q

Open cohort

A

people can enter study at any time

86
Q

Prevalence =

A

number of cases / population

87
Q

Retrospective cohort study

A

Disease outbreak is already occurring - how can we determine exposures?

88
Q

Niche

A

set of environmental conditions within which organism can maintain populations without immigration

89
Q

Statistical models

A

Correlation between relevant environmental dimensions and know point-occurance data

90
Q

Risk factor

A

a variable associated with an increased risk of disease or infection. (influenced by exposure and/or susceptibility)

91
Q

Susceptible hosts

A

What was the exposure? - Entry of disease agent - activity of host - Travel of host Host immune status

92
Q

Risk calculation

A

n = a + b (( b is negatives, a = positives)) = # of positive samples / # of exposed

93
Q

Risk rate ratio calculation

A
  • type of ratio comparing the change in one value (numerator) per change in another value (denominator) - Delta a / delta b
94
Q

Risk ratio calculation =

A
  • risk in group 1 (exposed) / risk in group 2 (non-exposed)
95
Q

Risk ratio

A

Disease/exposed = a No disease/ exposed = b Disease/ not exposed = c No disease/not exposed = d Risk to exposed = a/(a+b) Risk to not exposed = c/(c+d) Risk ratio = [a/(a+b)] ÷ [c/(c+d)]

96
Q

What does Risk ratio tell us?

A

RR = 1, exposure has no association RR > 1, exposure positively associated with disease RR< 1, exposure negatively associated with disease

97
Q

Batrachochytrium dendrobatidis

A

The Chytrid fungus, a non-hyphal zoosporic fungus. Fungus that killed a bunch of frogs

98
Q

How many emerging infectious diseases are zoonotic?

A

73%

99
Q

Majority of EIDs are:

A

bacterial or rickettsial

100
Q

Best global predictors of EIDS?

A

Mammal species richness

101
Q

Biodiversity should generally

A

reduce the prevalence of infectious diseases

102
Q

The Iceberg Model

A
  • What appears, visible behaviors. vs what’s below - Need to see the whole system “Beneath the visible level of events and crisis, there are underlying structures, paradigms of thought, and sources that are responsible for creating them.”
103
Q

Practice an SIR model

A

now

104
Q

Diseases eradicated by humans

A
  • Measles - Rinderpest ( Morbillivirus)
105
Q

Incubation period

A

between infection and symptoms

106
Q

latent period

A

between infection and infectious

107
Q

Index case

A

first initial case

108
Q

Ro > 1 =

A

disease outbreak

109
Q

Ro < 1 =

A

disease fades out

110
Q

Ro =

A

average number of secondary infectious cases produced by an index case in a SUSCEPTIBLE population

111
Q

Ro conditions =

A
  • beginning of an epidemic - fully susceptible population - no control measures
112
Q

SIR stands for

A
  • Susceptible (uninfected, not exposed) - Infected - Removed (post infection, dead, recovered and resistant)
113
Q

SIR model assumes

A
  • well-mixed populations - closed population (no immigration, births, etc) - etc
114
Q

Ro calculation is =

A

= dcp = Duration of infectiousness x contact rate x transmission probability .

115
Q

Effective reproductive number =

A

R = average number of secondary infectious cases produced by infectious cases – Conditions: uncontrolled disease spread

116
Q

CONTROL reproductive number =

A

Rc = effective reproductive number in the presence of control measures — conditions: control measures instigated

117
Q

How to reduce R?

A

Reduce: 1. # of susceptible hosts 2. sources of infection 3. Infectiousness 4. contact rates 5. INTERUPT transmission 6. INCREASE herd immunity

118
Q

Basic methods of disease control

A
  1. isolation 2. vaccination 3. barriers 4. eradication (disinfectant, culling) 5. treatment 6. education
119
Q

Reduce Ro?

A

Altering: 1. duration of infectiousness 2. contact rate 3. transmission probability

120
Q

Basic anatomy of disease

A
  1. susceptible hosts 2. disease agent 3. reservoir / source 4. entry into susceptible host 5. exit from infected host 6. mode of transmission
121
Q

Threshold theory and vaccination equation

A

v > 1 - ( 1 /Ro ) v = proportion of population that are vaccinated

122
Q

Herd Immunity Threshold

A

Vaccinating a proportion (or herd) of the population protects unvaccinated individuals.

123
Q

Risk calculation =

A

= a / n a = positive samples n = sample size of EXPOSED persons n = a + b b = negatives

124
Q

Risk ratio =

A

risk in group one (exposed) / risk in group two (non-exposed)

125
Q

Epidemiological surveillance

A

ongoing systematic collection, analysis, and interpretation of health data essential to the planning, implementation, and evaluation of public health practice closely integrated with the timely dissemination of these data to those who need to know. (CDC)

126
Q

Epidemiological process with surveillance

A
  1. describe disease risks and trends (surveillance) 2. evaluate control/prevention (surveillance)
127
Q

Types of surveillance

A
  1. passive 2. active
128
Q

Passive surveillance

A

Health officials report cases of illness, but no special effort is made to find unsuspected disease incidents. PRO: inexpensive, not geographically restricted CON: may under report, replies on person motivation

129
Q

Active surveillance

A

Field investigation of disease incidence, e.g. interviews, screening, sampling PRO: accurate, high standards CON: expensive, time consuming, geographically restricted

130
Q

endemic

A

normal, baseline, natural distribution/rates of disease

131
Q

cluster

A

observation of above-normal number of cases

132
Q

outbreak

A

sudden increase in disease cases

133
Q

epidemic

A

outbreak on large scale

134
Q

pandemic

A

outbreak at international/global scale

135
Q

intrinsic incubation period

A

interval between the acquisition of an infectious agent by a vector and the vector’s ability to transmit the agent to other susceptible vertebrate hosts

136
Q

Incidence

A

Number of new cases that occur during a specified period of time, in a population at risk for developing the disease. PERSON-TIME @ risk

137
Q

Person-time units

A

length of time individuals are in states of health, exposure (at risk), infection, infectiousness, etc. (or how many people and for how long??) – 10 people studied for 6 weeks. = 60 person-weeks

138
Q

Trophic Cascade

A

indirect top-down regulation of productivity, abundance or biomass at one trophic level (e.g. primary producers) by higher-level consumers at least one trophic level removed (e.g predators)

139
Q

Muskox Lung worm

A

Umingmakstrongylus Pallikuukensis

140
Q

Life-cycle stages of tick?

A

Eggs, 6-legged larva, eight-legged nymph, adult

141
Q

Nymphal Infection Prevalence (NIP)

A

infected nymphs / number of nymphs

142
Q

Number of infected nymphs = (NIN) =

A

Density of host species x species-specific larval burdens x #of larvae infected by host species (reservoir competence) x Species-specific molting success.

143
Q

CALCULATE ! Body burden = 27.8 (se 3.3) larvae Molting % = 41.5 (3.5) Reservoir competence (%) = 92.1 (2.9) Density/ha = 0-100 – 20 mice/ha, what should the NIP be?

A

Body burden = 27.8 (se 3.3) larvae Molting % = 41.5 (3.5) Reservoir competence (%) = 92.1 (2.9) Density/ha = 20 Number of infected nymphs = 20 * 27.8 * 0.415 * 0.921 = 213 Number of nymphs = 20 * 27.8 * 0.415 = 231 NIP = 213/231 = 92.2%

144
Q

CALCULATE ! Body burden = 36.0 (11) larvae Molting % = 41.2 (6.0) Reservoir competence (%) = 55.0 (6.4) Density/ha = 0-50 – 20 mice/ha, what should the NIP be?

A

Body burden = 36.0 (11) larvae Molting % = 41.2 (6.0) Reservoir competence (%) = 55.0 (6.4) Density/ha = 20 Number of infected nymphs = 20 * 36.0 * 0.412 * 0.55 = 163 Number of nymphs = 20 * 36.0 * 0.412 = 297 NIP = 163/297 = 54.9%

145
Q

Density of infected nymphs (DIN)=

A

Number of infected nymphs / ha

146
Q

Is there a predictable relationship between biodiversity and disease risk ?

A

No, but understanding local community ecology can help in the prediction of disease dynamics.

147
Q

Meta-analysis, study requirements :

A
  1. human pathogen 2. simultaneous measurement of pathogen abundance & host diversity - test statistics : F, X^2, t, r^2
148
Q

Clinical symptoms of muskox lungworm

A

respiratory compromise, predisposition to being preyed upon

149
Q

Lyme Disease

A

An emerging infectious disease - Borrelia Burgdorferi

150
Q

Lyme disease range expansion?

A

Land-use change population density surveillance case definitions media deer coyotes tick populations

151
Q

Dengue

A

*flu-like illness * 50 -100 million infections estimated annually * over 100 endemic countries * 1/2 the world population at risk *incidence has increase 30-fold in last 50 years

152
Q

Lyme disease agent

A

Spirochete bacterium Borellia Burgdorferi

153
Q

Lyme disease mode of transmission and reservoir?

A

Vector-borne (ticks) reservoir rodents

154
Q

When Ticks molt its called..

A

Trans-stadial transmission

155
Q

What do maps tell us?

A
  • they give us insight into disease ecology and disease risk - show us the importance of local context & scale
156
Q

Lyme diagnostics

A

B burgdorferi - more detectable in EPB B miyamotoi - more detectable in blood

157
Q

Small animals of California oak woodlands.

A

Western fence lizard - high tick burden Western gray squirrel - high pathogen transmission

158
Q

“To win the disease battles of the 21st century while ensuring the biological integrity of the Earth for future generations requires interdisciplinary and cross-sectoral approaches to disease prevention, surveillance, monitoring, control and mitigation as well as to environmental conservation more broadly.” - Wildlife conservation society

A

“To win the disease battles of the 21st century while ensuring the biological integrity of the Earth for future generations requires interdisciplinary and cross-sectoral approaches to disease prevention, surveillance, monitoring, control and mitigation as well as to environmental conservation more broadly.” - Wildlife conservation society

159
Q

Extrinsic incubation period

A

The time between when a mosquito acquires an infection agent and the mosquito’s ability to transmit the agent to other susceptible hosts