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2052 DYLAN > epidemiology > Flashcards

epidemiology Flashcards

1
Q

Epidemiologists

A
  • Study positive health states
    • Discover agent of disease, environmental factors
    • Determine patterns
    • Identify segments of population at risk
      Health programs or services to improve health
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2
Q

Cholera 1800s vs 2020

A
  • Better knowledge of outbreak
    • Germ theory in early phase
    • Widespread, high mortality vs ~200,000 deaths/yr.
    • Water from Thames vs separate water supply
      Not efficient sewage system vs efficient
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3
Q

Epidemiological triangle

A
  • Infectious agent - virus, bacteria, parasite etc.
    • Host
      ○ Demographic factor - e.g. age, ethnicity
      ○ Biological and genetic factor - e.g. blood group, immunity
      ○ Behavioural and cultural - smoking, alcohol, diet
    • Environment
      ○ Physical, chemical, biological
      ○ Environment - geology, climate, vectors
      Socioeconomic - occupation, income, access to services
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4
Q

Pathogen - effect of dose

A
  • Shorter incubation period when increased does of Salmonella
    Incubation period - time from pathogen exposure to onset of signs and symptoms
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5
Q

Risk

A
  • Modifiable = potential to improve health
    ○ Usually environmental - climate change, agriculture, individual behaviours
    Unmodifiable risk factors = less able to improve health - geneitic
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6
Q

mortality vs morbidity

A

amount of death due to disease

amount of illness due to disease

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7
Q

elimination vs eradication

A

reduction to zero in geographic location

complete and permanent reduction to zero

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8
Q

Disease burden

A
  • Measure of impact of living with disease
    • Measure of gap between current health and ideal health
    • Financial cost, morbidity, mortality
      Measurement = disability- adjusted life years (DALYs) - years healthy life lost due to illness and death
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9
Q

Prevalence

A
  • Proportion of population with disease at specific time
    • Snapshot
      Number of ppl at a specific time with disease / total number of people in the population at risk
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10
Q

Incidence

A
  • Number of new cases over a period of time
    • Presented as proportion or rate measurement
      Indication of infection risk with a specific time
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11
Q

Prevalence vs incidence

A
  • Allows comparison among different populations
    • Prevalence measures existing disease
    • Incidence measure rate at which new cases occur
    • If incidence increases, prevalence increases
    • If prevalence is introduced (eg vaccine, quarantine), incidence will decrease
    • If effective treatment is found, prevalence will decrease
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12
Q

levels of outbreak

A

Pandemic - all
Epidemic - outbreak
Endemic - expected level
Sporadic - occurs infrequently

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13
Q

sporadic level

A

occasional cases occurring at infrequent intervals (low level)

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14
Q

endemic level

A

Persistent occurrence - baseline - low to moderate

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15
Q

epidemic level

A
  • Increase in expected level - can be rapid - large number of cases in short period
    • Clusters
    • Conditions
      ○ Agent +susceptible host in reasonable numbers
      ○ Change to infectious agent - increase in amount, fast incubation
      ○ New disease in naïve population
      ○ Mode of transmission
      Opportunities for exposure - slow recognition
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16
Q

pandemic level

A
  • Over several countries

Large number of people

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17
Q

Exposure

A
  • Host and infectious agent encounter each other
    • Possible outcomes
      ○ No infection
      ○ Death - clinical
      ○ Recovery + immunity - clinical
      Immunity - subclinical
18
Q

Incubation period

A
  • 3-5 days average
  • From exposure to sign
    • Pathogen development but no clinical manifestations
    • Length
      ○ Virulence
      ○ Host health
      ○ Site
      Reproduction number
19
Q

Prodromal period

A
  • Clinical manifestation
    • Short period preceding illness
      Can be contagious
20
Q

Incubation period useful for:

A
  • Predict disease severity
    ○ Shorter incubation = more severe
    • Quarantine duration
      Interpret public health surveillance data
21
Q

Illness

A
  • Onset of symptoms
    • Most severe stage
      Immune response still being formed
22
Q

Decline

A
  • Returning to normal
    • symptoms reduce
      Or death
23
Q

Convalescent period

A
  • Recovery

Symptoms disappear

24
Q

The chain of infection - expanding infection triangle

A
  1. Source / reservoir
    1. Agent
    2. Transmission
    3. Portal of entry
    4. Susceptible host
      Portal of exit
25
Q

Source

A

location from which pathogen is transmitted to host
- Animate (humans, plant, animals)
○ Zoonosis (disease of animals transmitted to humans)
- Inanimate - soil, water, food, air

26
Q

reservoir

A

normal habitat where pathogen is normally found
- Sometimes same as source (human carrier of TB)
- Sometimes different from source (Hendra virus)
○ Reservoir - bats
○ Source of human infection = horses

27
Q

Direct or indirect by 4 main routes

A
  • Airborne
    • Contact
    • Vehicle
      Vector
28
Q

Direct

A
  • person to person - secretions, cells, air
    • Zoonosis
      Vertical transmission via placenta
29
Q

Indirect

A

one host to another via intermediate (vehicles)

Intermediate can be animate (e.g. mosquito) or non-living (e.g. Doorknob)

30
Q

Airborne (Water droplets)

A
  • Large respiratory droplets (5-10 micrometre diameter)
    ○ Singing, talking, coughing, sneezing
    • Aerosols (1-5micrometre in diameter
      ○ Talking and breathing
      ○ Long time (hours to days)
      Reservoirs - air conditioning cooling towers e.g. legionnaires
31
Q

airborne (dust)

A
  • Become airborne due to disturbance, survive long
    • Fungal infections
      Hospital acquired
32
Q

Vehicles

A
  • Surgical instruments
    • Cosmetics
    • Clothing
    • Phones
    • Food
    • Soil
      Blood products
33
Q

Vector

A
  • Insects - malaria
    • Ticks - Lyme
    • Fleas - plague
    • External transmission - passive carriage on body surface - shigellosis
    • Internal transmission - carried inside vector - malaria
34
Q

Portal of entry

A
  • Oral route - food borne, water borne
    • Respiratory - dust, droplets
    • Urogenital - genital
    • Parenteral - injection to bloodstream - needles
    • Conjunctival - surface of eyes
      Dermal - skin - bite
35
Q

primary vs index vs secondary case

A 
Primary case
	- First case in population
Index case
	- First case reported to authorities
Secondary
Cases resulting from subsequent transmission
36
Q

Reproduction rate (R0)

A
  • Indicate how contagious the disease is
    • R0 assumes population is completely vulnerable (no immunity, no vaccine)
    • If R0 = 1, each infection causes one new infection
    • If R0 <1, disease declines
    • If R0 >1, disease increases, may result in outbreak
      The larger R0 the more contagious
37
Q

Re and R0 factors

A 
Re (effective) is used when there is some immunity or intervention measures
R0 = not measurement of time or severity
Factors
	- Duration
	- Infectivity
	- No. of contacts
	- Host factors - health
Climatic factors
38
Q

immunity

A
  • The capacity of a person when exposed to an infectious agent to remain free of infection
    • Can be acquired prior infection or immunisation
    • Varies for different diseases
      ○ Measles- experience it once, immunity life long
      Whooping cough - immunity can wain from previous infection
39
Q

herd immunity

A
  • Immunity of a group or community
    • Resistance to infection of a high proportion of individuals of a group
    • Resistance is a product of the number of susceptible people and the probability that those whose are susceptible will come into contact with an infected person
      1-1/R0
40
Q

Ten steps of treating an outbreak

A
  1. Establish existence of outbreak
    1. Research the disease, fieldwork
    2. Verify diagnosis
    3. Define and identify cases = case definition - speak to patients
    4. Use descriptive epidemiology - who, what, when, where, why, how
    5. Develop hypotheses
    6. Evaluate hypotheses
    7. Refine hypotheses
    8. Implement control and prevention measure - prevent additional cases
  2. Develop policies and communicate findings - health policies, education

2052 DYLAN (12 decks)

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