Epidemiology 1

Front 1

who studied the London cholera epidemic in 1854 and invented the 2 X 2 square for evaluation of an epidemic?

Back 1

John Snow

Front 2

What is the unit of concern of a clinician versus an epidemiologist?

Back 2

clinical: individual sick animal

epi: population of all animals: healthy, sick, and dead

Front 3

What is the primary objective of a clinician versus an epidemiologist?

Back 3

clinician: treat and cure the sick animal

epi: maintain population health; prevent & control

Front 4

What is the setting of a clinician versus an epidemiologist?

Back 4

clinician: hospital

epi: field (farm/kennel); setting where the disease occurs

Front 5

What are the questions asked by a clinician versus an epidemiologist?

Back 5

clinician:
- what is the disease?
- how do I treat it?

- epi:
- what is the disease?
- who? where? when?
- causes (why?)
- how to prevent / control the disease

Front 6

What is the diagnostic process of a clinician versus an epidemiologist?

Back 6

clinical:
- evaluate signs
- name the disease

epi:
- evaluate frequency of disease occurrence
- study patterns
- temporal, spatial, animal determinants for intervention

Front 7

what are the five primary goals of epidemiology?

Back 7

1. investigate/control disease with an unknown cause
2. determine origin and "behavior" of disease with a known cause
3. acquire and analyze data, produce infromation
4. assess economic impact of health and disease control
5. design and monitor intervention strategies

Front 8

what are the three primary qualitative components of epidemiology?

Back 8

1. what is the agent?
2. how does it propagate
3. how is it manipulated in a population?

Front 9

what are the four primary quantitative components of epidemiology?

Back 9

1. how often does it occur?
2. how rapidly does it spread?
3. "how much" are different populations/groups affected?
4. how great is the impact of prevention/control?

Front 10

what are the four levels of disease occurrence?

Back 10

1. endemic
2. epidemic/outbreak
3. pandemic
4. free

Front 11

what are the x- and y-axis of an epidemic curve?

Back 11

x-axis: time
y-axis: number of new cases

Front 12

what epidemiologic figure does an epidemic curve plot?

Back 12

incidence

Front 13

an ongoing or usual presence of a "disease" in a community or group of people, animals, plants, or region, at a "constant" level or pattern of "occurrence"

Back 13

endemic

Front 14

what are the three major types of endemic patterns?

Back 14

1. sustained
2. seasonal
3. sporadic

Front 15

what is the term associated with the way an endemic disease propagates and sustains itself?

Back 15

endemic chain of transmission

Front 16

what factor generally determines whether a disease is an epidemic?

Back 16

when the number of new cases CLEARLY exceeds the expected number of new cases in a population

Front 17

if an endemic disease was plotted on an epidemic curve for several years, what occurrence would signal an epidemic/outbreak?

Back 17

if the number of new cases exceeded the epidemic threshold of the curve

Front 18

what was critical for stopping the pandemic spread of the Black Plague?

Back 18

cutting off trade routes

Front 19

what is Phase 1 of the WHO's pandemic phase description of influenza?

Back 19

a virus discovered in animals has not yet been reported to infect humans

Front 20

what is Phase 2 of the WHO's pandemic phase description of influenza?

Back 20

an influenza virus circulating in animals has been reported to infect a human.

Front 21

what is Phase 3 of the WHO's pandemic phase description of influenza?

Back 21

animal or human-animal influenza has caused sporadic disease or small clusters of disease, but there is not sufficient human-to-human infection to sustain the outbreak

Front 22

what is Phase 4 of the WHO's pandemic phase description of influenza?

Back 22

human-to-human contact can sustain the outbreak

Front 23

what is Phase 5 of the WHO's pandemic phase description of influenza?

Back 23

the identified virus has caused sustained community-level outbreaks in two or more countries in one single WHO region.

Front 24

what is Phase 6 of the WHO's pandemic phase description of influenza?

Back 24

the identified virus has causes sustained community-level outbreaks in more than one WHO region

Front 25

what is the Post-Peak Period of the WHO's pandemic phase description of influenza?

Back 25

levels of pandemic in most countries have dropped below peak levels

Front 26

what is the Possible New Wave of the WHO's pandemic phase description of influenza?

Back 26

after the Post-Peak period, a resurgence of disease is observed.

Front 27

what is Post-Pandemic Period of the WHO's pandemic phase description of influenza?

Back 27

levels of influenza have returned to normal endemic levels in most countries

Front 28

what is the primary case?

Back 28

Primary case is the very first case that occurred; it may not be the first case reported (that is the index case)

Front 29

what is the index case?

Back 29

Index case is the first case reported (may be later than the primary case; primary case may be at an earlier date, but reported earlier)

Front 30

what is the basic reproduction number, R0, and how is its value interpreted?

Back 30

R0 = if you introduce the disease into a naïve population, what is the average amount of infections?

o If R0 = 1, then it passes from one individual to another single individual
o If R0 < 1, then it disappears
o If R0 >1 then it infects multiple hosts from a single person

Front 31

what are the three things/factors required for a disease outbreak?

Back 31

1. agent
2. host
3. environment

Front 32

what is the seasonal balace of an epidemic curve? what is the epidemic threshold?

Back 32

In an endemic disease:

seasonal balance is the moving average curve of new disease occurrences over time

epidemic threshold is a curve that lies 1.645 standard deviations above the seasonal threshold curve

Front 33

what is infectiousness?

Back 33

refers to the timing and amount of shedding of an infectious organism of a host.

Front 34

what is infectivity?

Back 34

the property of a pathogen in that how many organisms are required to successfully infect a host.

Front 35

the time from infection to clinical signs of disease

Back 35

incubation period

Front 36

what is the difference between a point common source and a continuous common source?

Back 36

a point common source is one single isolated exposure from a source, whereas continuous common source is repeated exposures of the same thing from that common source.

examples:
- point common source: one group of people getting food poisoning from a single pizza one single time.

- continuous common source: people split up the pizza, take it home, eat it over a period of several days and repeatedly infect themselves.

Front 37

what does the Reed Frost Model predict and what are its variables?

Back 37

predicts the number of new cases for a propagating epidemic

variables:
- number of new cases in the previous time period
- the number of susceptibles (those that are not already infected or resistant)
- the probability of effective contact

Front 38

in a Reed-Frost type of epidemic curve, why do the number of predicted new cases drop off after a peak?

Back 38

because the number of susceptibles decreases (susceptibles are those that don't have the disease and are not resistant to the disease)

Front 39

what four primary effects determine the probability of effective contact?

Back 39

1. infectivity (how many organisms are required to infect)
2. population density
3. # of susceptibles and immunes
4. interaction patterns

Front 40

what is herd immunity?

Back 40

the indirect protection of susceptible individuals brought about by the presence of immune individuals (e.g. reduces the probability of effective contact)

Front 41

what is the vaccination threshold and how is it calculated?

Back 41

the proportion of a naive population that must be vaccinated to prevent an outbreak.

VT = 1 - 1/R0

Front 42

what are the four phases of a typical epidemic growth curve?

Back 42

1. establishment - random effects
2. exponential growth
3. exhuastion of susceptibles
4. equilibrium/endemicity or recurrent epidemics

Front 43

what is prevalence?

Back 43

the probability of having a disease at a particular point in time; the number of cases in a total population

Front 44

what is incidence?

Back 44

number of new cases in a known population during a specific period of time

Front 45

how is prevalance calculated?

Back 45

number of diseased
--------------------------
total population

Front 46

how is incidence risk calculated?

Back 46

number of new cases
-----------------------------
all susceptible animals free of disease at the beginning of the period

Front 47

what is incidence risk?

Back 47

the risk of developing a disease over a given time period

Front 48

what is incidence density

Back 48

the rapidity with which new cases develop over a calculated time period

Front 49

how is mortality risk calculated?

Back 49

number of deaths over a time period
------------------------------------------------
the number of susceptibles and infected

Front 50

what is the case fatality risk?

Back 50

the proportion of those that die from a disease in those that are infected with the diesase

Front 51

what is latency?

Back 51

the time between infection and clinical signs of a BACTERIAL infection

Front 52

what is prepatency?

Back 52

the time between infection and clinical signs of a PARASITIC infection

Front 53

what is eclipse?

Back 53

the time between infection and clinical signs of a VIRAL infection

Front 54

how do you calculate prevalence odds?

Back 54

prevalance
-----------------
1-prevalence

Front 55

how do you calculate risk odds?

Back 55

risk
-------
1-risk

Front 56

a group within a population that has a particular property in common (e.g. age, breed, gender)

Back 56

strata

Front 57

what is standardization?

Back 57

comparing the level of disease in different populations by adjusting for differences in the populations, such as age. It calculates the COMBINED RATE/RISK

Front 58

how does direct standardization differ from indirect stndardization?

Back 58

direct standardization compares populations to each other and adjusting for strata in both populations.

indirect standardization uses a well-defined "reference population" to make the comparison. It calculates the EXPECTED RATE/RISK (e.g. the expected incidence density).

Front 59

what is the standard morbidity/mortality ratio

Back 59

in an indirect standardization, the number of observed cases diveded by the amount of expected cases (from the reference population)

Front 60

what is Risk Difference, and how is it calculated?

Back 60

the absolute proportion of disease cases directly attributed to exposure.

RD = (number of diseased/number of exposed) - (number of diseased/number not exposed)

Front 61

How is Odds Ratio calculated?

Back 61

odds of disease in exposed animals
------------------------------------------------
odds of disease in non-exposed animals

Front 62

How is Risk Ratio calculated

Back 62

the risk of disease in exposed animals
------------------------------------------
the risk of disease in non-exposed animals

Front 63

if x animals are diseased and y animals are not diseased:
- calculate the risk
- calculate the odds

Back 63

Risk = x / (x+y) - it is the proportion of diseased of the total population

odds = x / y - it is the number of animals that are diseased for every animal that is not sick

Front 64

What are the four Koch postulates?

Back 64

A living agent is causal for a disease if:
1. It is present in all cases of the disease
2. It does not appear in other diseases
3. It can be isolated in pure culture
4. when inoculated in susceptible host creates the same disease from which it can be reisolated

Front 65

an invertebrate that is capable of transmitting an infectious disease agent among vertebrates.

Back 65

vector

Front 66

an animate (or inanimate) object on or in which an infectious agent usually lives and depends for survival, and which therefore is often a source of infection by the agent.

Back 66

reservoir

Front 67

host who contains / harbors, and may spread an infectious disease agent

Back 67

carrier

Front 68

what are the four time scales (courses) of clinical disease?

Back 68

1. Peracute - very rapid onset and progress of symptoms (24 -48 hours)
2. Acute - rapid onset and progression (days)
3. Sub-acute - slower
4. Chronic - slow prolonged course of disease over months or years`

Front 69

a cause, if when absent, the expected/resulting effect will not occur

Back 69

necessary cause

Front 70

a cause, if when present, the expected/resulting effect will occur

Back 70

sufficient cause

Front 71

what are the three components of the epidemiologic triad and what are some basic components that are determinants of health/disease?

Back 71

1. host: species, breed, gender, age, size, conformation, use, behavior, nutrition, immune status

2. agent: virulence, pathogenicity, gradient and outcome of infection (e.g. host response, reservoirs, severity), mode of transmission

3. environment: physical location, climate, husbandry practices, stress

Front 72

what is transmissibility?

Back 72

how "well" can an organism be infected by an infectious agent

Front 73

what is virulence?

Back 73

how severe are the effects of an infectious agent

Front 74

what is pathogenicity?

Back 74

the proportion of infected animals that become ill

Front 75

what are the three measures taken to prevent the spread of infectious disease?

Back 75

1. exclusion
2. containment
3. elimination

Front 76

what are the four major ways by which disease spreads?

Back 76

1. direct fecal-oral
2. direct aerosol
3. direct contact with bodily fluids
4. direct skin contact

Front 77

what are the four major ways in which to exclude an infectious agent?

Back 77

1. prevent introduction (e.g. hand washing, protection)
2. vector control
3. vaccination
4. quarantine

Front 78

what are the three major ways to eliminate disease from an area (not animals)

Back 78

1. cleaning
2. disinfecting
3. drying

Front 79

what are the four VMRCVM teaching hospital biosecurity protocols?

Back 79

2. Green Dot – Healthy animals, elective surgeries

1. Yellow Dot – neonates, geriatrics, immunocompromised.

3. Orange Dot – Potentially contagious / infectious

4. Red Dot – Known contagious / infectious