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HLTC27: Epidemiology > Lecture 10: Infectious Disease Epidemiology > Flashcards

Lecture 10: Infectious Disease Epidemiology Flashcards

1
Q

History of Infectious Disease

A

1350BCE - smallpox
1400s - bubonic plague
1500s - syphillis
1900s - smallpox, cholera, typhoid, tuberculosis

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2
Q

Susser’s Era in Epidemiology

A

Through different paradigms and intervention strategies, we have new understandings of infectious diseases.
Eras include:
- Sanitary
- Infectious Disease
- Chronic Disease
- Eco-epidemiology

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3
Q

Sanitary era (paradigm, analytic approach, prevention)

A

paradigm - miasma theory
analytic approach - clustering of mortality
prevention - sanitation

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4
Q

infectious disease era (paradigm, analytic approach, prevention)

A

paradigm - germ theory
analytic approach - laboratory
prevention - vaccinations

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5
Q

Chronic Disease era (paradigm, analytic approach, prevention)

A

paradigm - black box
analytic approach - risk ratios
prevention - host, agent, environment

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6
Q

Eco-epidemiology era (paradigm, analytic approach, prevention)

A

Paradigm - systems theory
analytic approach - determinants at many levels
prevention - contextual to molecular

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7
Q

system theory

A

there are a multitude of risk factors in various systems. Ex. transportation, government, healthcare, etc.

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8
Q

Infectious disease

A

An illness due to a specific infectious agent or its toxic products.
Arises through transmission of agent/toxic product from infectious person/animal/reservoir to a susceptible host.

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9
Q

How can transmission happen?

A
  • directly, from other infected animals/humans
  • indirectly, from intermediate host, vector, or the environment
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10
Q

Susceptible

A

uninfected, but able to become infected if exposed

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11
Q

Infectious

A

infected and able to transmit infection to other susceptible individuals

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12
Q

Immune

A

possessing cell-mediated or humoral or antibody protection against an infection

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13
Q

diseased/clinical infection

A

presence of clinical signs of pathology (A disease that has recognizable clinical signs and symptoms)

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14
Q

Latent infection/subclinical infection

A

Remains in the body but you are not infectious

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15
Q

Carrier

A

Protracted infected state with shedding of the infectious agent.

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16
Q

Epidemic

A

excess in occurrences of cases beyond of what is normally expected in a community or region

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17
Q

Outbreak

A

an epidemic limited to localized increase in the incidence of a disease

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18
Q

Endemic

A

The constant presence of a disease or infectious agent within a given geographic area or population group

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19
Q

Pandemic

A

An epidemic crossing international boundaries and affects many people

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20
Q

Pathogens

A
  • bacteria
  • virus
  • chemical toxins
  • parasitic (multi-cell)
  • Fungal
  • Protozoa
  • Prions
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21
Q

Bacteria

A
  • fatty membrane contains DNA and cellular machinery
  • obtain energy from sugars, fats, and proteins
  • live and multiply outside of host
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22
Q

Different Shapes of Bacteria

A

bacilli - rod shape
cocci - round
spirochete - spiral

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23
Q

virus

A
  • not affected by antibiotics
  • smallest infectious disease agent
  • thin protein coating around genetic material
  • requires energy from host cells
  • cannot replicate outside host cell
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24
Q

Chemical toxins

A
  • organic and inorganic
  • allergens, carcinogens, teratogens
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25
Q

Parasitic (multi-cell)

A
  • defined nucleus
  • single or multi-celled
  • ex. malaria, head lice
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26
Q

Fungal

A

includes yeast infections, candida

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27
Q

Protozoa

A
  • single cell organisms
  • can be free-living or parasitic in nature
  • transmission - live in a human’s intestine; fecal-oral route
28
Q

Prions

A
  • relatively new discovery
  • non-living
  • infectious agent with protein-like qualities
  • thought to be responsible for mad cow disease
  • difficult to disinfect
  • Ex. TSEs
29
Q

Transmission Routes

A

Direct Transmission
Indirect Transmission

30
Q

Direct Transmission Routes

A
  • mucous membrane to mucus membrane (STD)
  • Across placenta
  • Transplants
  • skin to skin
  • Sneezes, coughs
31
Q

Indirect Transmission Routes

A
  • water-borne
  • proper air-borne
  • food-borne
  • vectors
  • objects
32
Q

Six-Link Chain of Infection

A

These interactions cause communicable disease to occur:
1. Pathogens
2. Reservoir
3. Portal of Exit
4. Transmission
5. Portal of Entry
6. Susceptible Host

33
Q

Pathogens (Definition and public health approach)

A
  • virus, bacteria, or parasite that causes disease in humans
  • kill agent (antibiotics)
34
Q

Reservoir (definition and public health approach)

A
  • location which pathogen lives and reproduces
  • eliminate reservoir (remove garbage)
35
Q

Portal of Exit (Definition and public health approach)

A
  • route pathogen takes to leave infected host
  • knowledge to understand transmission and control
36
Q

Transmission (Definition and Public Health Approach)

A
  • method of traveling from reservoir/infected host to susceptible host
  • block movement of pathogen (quarantine)
37
Q

Portal of Entry (Definition and Public Health Approach)

A
  • route pathogen enters host
  • block point of entry (mask)
38
Q

Susceptible host (Definition and Public Health Approach)

A
  • entry into host that is not immune
  • improve resistance (vaccination)
39
Q

Characteristics of Agent

A
  • toxicity, virulence, infectivity
  • susceptibility to antibiotics
  • ability to survive outside body
40
Q

Characteristics of Environment

A
  • climate
  • physical structures
  • population density
  • social structure
41
Q

Characteristics of Host

A
  • age
  • prior exposure
  • susceptibility
  • co-infection
  • immune response
42
Q

Interventions for agent

A
  • eradicate
  • genetically modify
43
Q

Interventions for environment

A
  • housing quality
  • sanitation, water
  • prevention services
44
Q

Interventions for Host

A
  • treat, isolate
  • immunize
  • nutrition
45
Q

Age-environment intervention

A
  • remove breeding grounds
  • improve sanitation
46
Q

Host-environment intervention

A
  • educate
  • change activity patterns
  • quarantine
47
Q

Host-agent intervention

A
  • protect
  • educate
  • alter exposure
48
Q

Surveillance of Infectious Diseases

A
  • influence decreased 2020-2021
  • peaks end of december and early january
  • increasing after that
  • STIs have increased such as Gonorrhea and Chlamydia
49
Q

Coronaviruses

A

group of viruses that are common in humans and are responsible for up to 30% of common cold

50
Q

Outbreaks that have occurred due to coronaviruses

A

SARS (2003)
MERS (2012)

51
Q

COVID-19 Seroprevalence in Ontario

A
  • PHO created the COVID-19 serosurveillance program
  • see what proportion of the Ontario population was infected with COVID and developed the antibodies for it
52
Q

Serology Testing

A

a lab test that measures the antibodies specific to Covid-19
(looks as the presence or levels of antibodies)

53
Q

Investigation and Control of Epidemics/Pandemics

A
  1. Investigation
  2. Identifying cases
  3. Management and Control
  4. Surveillance and Response
54
Q

Principles of Surveillance

A
  • incidence and prevalence
  • case-fatality
  • mortality rate and premature mortality
  • bed-disability days
  • medical costs
  • preventability
  • epidemic potential
  • information gaps on new diseases
55
Q

Sources of Data

A
  • mortality an morbidity
  • hospital records
  • laboratory diagnoses
  • outbreak reports
  • vaccine utilization
  • sickness absence report
  • biological changes in agent, vectors, or reservoirs
  • blood banks
56
Q

Factors that Influence Effectiveness of Surveillance Systems

A
  • Number of conditions (fewer)
  • Amount of information per case (little)
  • Burden on reporter (small)
  • Decision-Makers’ interest in surveillance data (high)
  • goals for surveillance (clear and support)
  • reporting strategy for serious but common conditions (enough to meet goals)
  • usefulness of data locally (high)
  • use is limited to analysis of data and archiving (data are well used)
  • usefulness to decision-makers for prevention action (high)
57
Q

Mathematical Models of Infectious Disease Transmission Dynamics

A

Systematic way of identifying and applying assumptions to data on disease transmission to quantify how an epidemic may evolve.

58
Q

What do mathematical models help with?

A
  • Estimating transmission parameters
  • effectiveness of interventions
  • predict cost effectiveness of interventions
59
Q

Reproductive Rate, R

A

Average number of new infections caused by 1 infected individual.

60
Q

Basic Reproductive Rate, R0

A

in an entirely susceptible population
> 1 = epidemic
1 = endemic
< 1 = infection dies out

61
Q

Effective Reproductive Rate, R

A

In a population where <100% is susceptible.

= proportion susceptible x R0

62
Q

Hallmarks of an epidemic

A
  1. number of infections increase exponentially during the early phase
  2. epidemic curve is unimodal and peaks when the susceptible pool has been sufficiently depleted (Rt < 1)
63
Q

Calculating R0

A

R0 = BcD

B = probability of transmission per contact
c = contact rate
D = duration of infectivity

64
Q

SIR model

A

People can be in one of three states

S - susceptible to the infection
I - infected/infectious
R - recovered/immune

65
Q

Assumptions for the SIR model

A
  • fixed population
  • latent period is 0
  • infectious period = disease period
  • after recovery, individuals are immune
66
Q

Herd Immunity

A

The proportion of the population that need to be immune in order to stabilize an infectious disease.
HIT = (R0 - 1) / R0
or
HIT = 1 - (1/R0)

67
Q

Things to consider when interpreting the herd immunity number

A

virulence of the disease
re-emergence
susceptibility
interventions in place

HLTC27: Epidemiology (5 decks)

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