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Flashcards in Epi Class 10 Deck (22):
1

Modes of Transmission

Direct (person-to-person) transmission
- Contact with blood or body fluids
- Sexual contact
- IDU (injecting drug use)
- Fecal-oral spread

Indirect transmission
- Airborne
- Vector-borne
- Vehicle-borne

Vertical transmission
- MTC

2

Reservoir

Where in the ‘environment’ is the infection found?

Examples:
- Soil
- Water
- Humans (anthroponosis)
- Animals (zoonosis)

3

Cycle of Infection: examples

Human – human – human

Vertebrate – vertebrate – human

Insect - human – insect – human

Complex cycles

4

Infection

agent reproduces inside a person

5

Infectivity

# infected / # exposed (and susceptible at time of exposure)

6

Do all exposure cause infection/disease?

Not all exposures cause an infection

Not all infections cause disease (symptoms)

7

Pathogenicity

# ill (symptomatic = diseased) / # infected

8

Virulence

# with severe illness or death / # with symptoms

High virulence will be associated with a high case fatality rate

9

Acute

short-term (measure with incidence)

10

Chronic

long-term (measure with prevalence)

11

Endemic

always present

12

Epidemic

more cases than normal

13

Pandemic

global epidemic

14

Surveillance

ongoing tracking through disease reports to catch outbreaks early

15

Disease Control


limit infection within an area

16

Elimination

no new cases of the infection in the area

17

Eradication

no new cases anywhere in the world

18

Extinction

not even stored samples in some refrigerator!

19

Epidemiologic Investigation

1. What is the case definition? (How will you know if someone has the disease of interest?)

2. Descriptive Epidemiology Triad:
- Person: Who participated in the study or event?
- Place: WHERE did the study or event occur?
- Time: WHEN did the study or event occur?

3. Analytic Epidemiology Triad: Agent – Host – Environment (AHE)
- WHY did the disease outcome occur in certain people or certain population groups?

20

Epidemic Curve: Point Source

One time exposure. Incidence dramatically peak at one point in time

21

Epidemic Curve: Continuous Source

Constant exposure. Incidence remains relatively consistent over time

22

Epidemic Curve: Person-to-Person

Waves of increasing size over time as people spread infection to larger and larger groups.

Person-to-Person epidemic curves can die out naturally if the whole population has been exposed/infected.