medsci 202 > lecture 14 > Flashcards

lecture 14 Flashcards

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1
Q

what is the disease triangle

A

shows that disease requires three interacting factors:
- a susceptible host
- a virulent pathogen
- a favorable environment

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2
Q

what do we look at for the virus in a disease triangle

A
  • the type and its virulence factors
  • route of transmission
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3
Q

what do we look at for the host in a disease triangle

A

risk factors

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4
Q

what do we look at for the environment in a disease triangle

A
  • socioeconomic conditions
  • geopolitical conditions
  • regulatory conditions
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5
Q

define outbreak

A

sudden increase in occurrence

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6
Q

define pandemic

A

outbreak that has spread across a wide region (doesn’t necessarily correlate with severity)

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7
Q

describe endemic

A

the baseline presence of a disease within a geographic area (e.g. flu)

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8
Q

what is pathogenesis

A

the mechanisms by which disease develops, progresses and either persists or is resolved

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9
Q

define virulence

A

a measure of the capacity of a pathogen to cause damage to the host

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10
Q

what are the different types of organism locations

A
  • free-living: out in the environment
  • facultative intracellular: free-living but can also live in a cell
  • obligative intracellular: require a cell to live in
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11
Q

what is a reservoir in epidemiology

A

“source”, where the infectious agent was caught from

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12
Q

example of reservoirs

A
  • zoonosis infections are caught by animals
  • human to human
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13
Q

what is transmission

A

how an infectious agent gets from the reservoir to the site of infection

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14
Q

what is host restriction

A

the limitation of a pathogen to infect a specific species or group of species

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15
Q

why is COVID difficult to eradicate

A

it is not host restricted, so even if human-human transmission is controlled, it can still be spread between other animals

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16
Q

what are sources of infectious agents

A
  • self and others
  • food and drink
  • environment
  • air
  • fomites (inanimate objects)
  • insects and animals
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17
Q

examples of transmission routes

A
  • airborne
  • direct contact
  • indirect contact
  • blood
  • faecal-oral
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18
Q

how are pathogens transmitted via air

A

respiratory droplets, spores

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19
Q

how are pathogens transmitted via direct contact

A

contact with self, others, animals

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20
Q

how are pathogens transmitted via indirect contact

A

fomites (e.g. coins, handles)

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21
Q

how are pathogens transmitted via blood

A
  • animal bites
  • insect bites
  • wounds
  • contaminated sharps
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22
Q

how are pathogens transmitted via faecal-oral routes

A
  • contaminated food/water
  • not washing hands after toilet
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23
Q

who is most at risk of diseases

A
  • the very young
  • the very old
  • the immunocompromised
  • contact/environment
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24
Q

why are the very young and old at risk of disease

A
  • very young: naive immunity
  • very old: “failing” immunity, winding down essentially
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25
why are the immunocompromised at risk for disease
- wound/surgery: route of transmission - drugs e.g. antibiotics, chemotherapy - existing condition
26
why do specific environments increase risk for disease
- lifestyle - occupation - location
27
what measures the infectiousness of a disease
R₀
28
how does R₀ work
the larger the R₀, the more contagious the disease is
29
give an example of R₀
if R₀ = 1, every person infected will infect one more person
30
what does R₀ depend on
- the microbe - the dose - the route of transmission - host susceptibility
31
what is "dose" in R₀
how much microbe required to cause disease
32
what's the realistic aspect of R₀
in 20% of cases, each individual ends up infected more people than the R₀ suggests
33
what is superspreading
when one individual spreads disease to a lot more people than R₀ suggests
34
what is Reff
- the effective R number - takes into account public health measures like vaccinations
35
what is the incubation period
- the time between exposure to an infectious microbe and onset of symptoms - can range from hours to years
36
can people be infectious in an incubation period
- yes - depends on microbe, dose, host susceptibility
37
what is onset of symptoms
when symptoms have started
38
what is clinical disease rate
the proportion of infected people who develop disease
39
what is the infection fatality rate
the number of estimated deaths as a proportion of all infected
40
what's a problem with the infection fatality rate
it's difficult to find the denominator, as we can't easily measure *everyone* infected - some people are asymptomatic, mild symptoms, etc.
41
what do we tend to use instead of infection fataility rate
case fatality rate
42
what is case fatality rate
the number of deaths as a proportion of *confirmed* cases
43
what is the immunity rate
the proportion of people immune to reinfection
44
describe the lifespan of an outbreak
1) phase 1: introduction of the disease, exponential rise in cases 2) phase 2: controls in place, developing immunity, peak has been reached 3) phase 3: no infectious/susceptible people left
45
how do diseases stop infecting
- sterilising immunity - no more hosts (isolating until virus dies, no one left to spread to)
46
do diseases usually die forever
no, what tends to happen is "waves" of infections - disappears, comes back, disappears, comes back, etc.
47
what causes "waves" of infections rather than the pathogen dying out
- reintroduction - waning immunity - pathogen evolution
48
what is the ebola virus disease
severe disease caused by orthoebolaviruses
49
where was ebola identified
in 1976, with simultaneous outbreaks in congo and sudan
50
what happened after ebole was identified in 1976
- no recorded human cases 1979-1994 - since 1994, increasing outbreaks
51
describe how ebola causes disease
1) virus attaches to TIM-1 receptors on the host cell 2) viral envelope fuses with host cell 3) viral RNA is released then converted into a positive-sense mRNA template 4) viral RNA is replicated inside the cell 5) new virus buds from the infected cell
52
how does ebola spread
- zoonosis: via animals, especially bats - then, human-human
53
how does ebola spread human-human
- contact with bodily fluids of the sick/dead - contact with contaminated objects
54
what is the ebola incubation period
2-21 days: no symptoms, no spread
55
what are the early symptoms of ebola
- last 0-3 days - fever, fatigue, headache, sore throat
56
what are the mid symptoms of ebola
- last 3-10 days - diarrhoea, vomiting, stomach pain, hiccups
57
what are the severe symptoms of ebola
- last 7-12 days - severe diarrhoea, vomiting, bleeding
58
what was the mortality rate of ebola
25-100%
59
when was the biggest ebola outbreak
2014
60
how many total cases of ebola were there in west africa 2014
>28,000 cases
61
why was the 2014 west african ebola outbreak surprising
it occurred in areas that had no previously documented cases of ebola
62
when did people "notice" the ebola outbreak
first case was dec 2013, but outbreak was confirmed in mar 2014
63
why did ebola spread so much in west africa
different practices in how to deal with dead bodies, compared to other countries (that had dealt with ebola)
64
what is the main treatments for ebola
- monoclonal antibodies: antibodies from someone who has survived the infection - vaccines
65
what are the vaccines used to treat ebola
- ERVEBO: has an ebola gene - zabdeno + mvabea combination vaccine
66
which vaccine works best for ebola
the ERVEBO vaccine only works against ebola zaire, while the combination vaccine works against more
67
how is the ERVEBO vaccine given
- 1 intramuscular dose for 18+ - revaccinate if contact infection >6 months after initial vaccination
68
how is the combination vaccine given
- 2 intramuscular doses for 1+ - zabdeno followed by mvabea 8 weeks later
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