Ch 16: Epidemiology Flashcards

1
Q

Epidemiology

A

Is the science of the cause, prevalence and spread of disease

Disease is a codition that negatively affects teh structure or function of all or part of an organism

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2
Q

What is the purpose of epidemiology

A

concerned with the geographical distribution of disease, the route of transmission, the maintenace of the disease in a population and practical methods to control or prevent outbreaks

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3
Q

Morbidity

A

state of being diseased

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4
Q

Morbidity rate

A

the number of diseased people in a population

usually / 100 000

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5
Q

Prevalence`

A

The number of pople with a particular disease in a population at a point in time

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6
Q

incidence

A

the number of new cases in a period of time

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7
Q

Mortality

A

the death of an individual

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8
Q

Mortality rate

A

the number of deaths in a population

usually / 100 000

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9
Q

Case-Fatality rate

A

the proportion of deaths due to a disease compared to the numner of diagnosed cases

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10
Q

What are the patterns of incidence

A

Sporadic

Endemic

Epidemic

Pandemin

Common source epidemic

Point source epidemic

Continuous common source spidemic

Propagated epidemic

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11
Q

What is the sporadic pattern of incidence

A

observed occasionally with no specific geographical location

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12
Q

What is the endemic pattern of incidence

A

disease present constantly in a geographical location, usually at a low prevalence rate

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13
Q

What is the epidemic pattern of incidence

A

a large or larger than normal number of cases in a short period of time in a specific geographical location

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14
Q

What is the pandemic pattern of incidence

A

an epidemic that occurs on several continents

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15
Q

Common source epidemic

A

there si a single source for all cases on infection

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16
Q

Point source epidemic

A

a common source epidemic where the source is limited in time, usually about the incubation period of the disease

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17
Q

Continuous common source epidemic

A

the source exists for an extended period of time

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18
Q

Propagated epidemic

A

person to person spread without there being a single source

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19
Q

Etiology

A

the study of the origin (of a diease in this case)

The ideaa that an infection disease is caused by a livign agent (germ theory)

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20
Q

Types of Epidemiological Studies

A

Observational

Descriptive

Retrospective

Prospective

Cohort

Case control

Cross sectional

Case Crossover

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21
Q

Observational Study

A

Signs and symptoms and personal data collected from (usually) a random selection of patients

no experimental manupulation

demonstrates only associations between disease and causative agents

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22
Q

Descriptive study

A

collects information about patients,disease signs and symptoms and daata about their lives whihc may have bearing

interviews and medical records

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23
Q

Retrospective study

A

data from the past applied to disease cases today

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24
Q

Prospective study

A

collect data from a group of people before anyone contracts the diease

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25
Q

Cohort

A

A group of people who ahare a common characteristic such as age

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26
Q

Case control

A

usually retrospective comparison between a group of people with the disease agaisnt a group of people who do not have the disease

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27
Q

cross sectional

A

compares randomly selected individuals with and without the disease at a single time point

to determine a characteristic that is associated with disease

28
Q

case crossover

A

each case of the disease is its own control

study each case during a time before disease and compare to after disease

29
Q

Odds Ratio

A

relative odds

a measurement of association used in case control studies

OR= (a/b) / (c/d)

a= number of exposed cases
b= the number of exposed controls
c= the number of not-exposed cases
d= number of not-exposed controls
30
Q

OR = 1

A

no association between exposure and outcome (disease)

31
Q

OR > 1

A

there is a positive association between exposure and outcome

32
Q

Risk Ratio

A

relative risk

a measurement of association used in cohort studies

RR = [a/(a+b))] / [c/(c+d)]

a= number of exposed cases
b= the number of exposed controls
c= the number of not-exposed cases
d= number of not-exposed controls
33
Q

RR = 1

A

no association between exposure and outcome (disease)

34
Q

RR >1

A

postivie association

35
Q

RR <1

A

negative association

36
Q

Attack rate

A

the cumulative percentage of people who get a diease over a period of time

the amount of people that aquire influenza over the course of the cold season

37
Q

Experimental studies

A

studies in a laboratory or slinical setting where the investigator manupulates a variable

Koch’s postulates often used in experimental studies

38
Q

Koch’s Postulates

A

The suspected pathogen must be found in evvery case of teh disease and not be found in healthy individuals

the suspected pathogen must be isolated and grown in pure culture

When teh suspected pathogen is inoculated into a healthy subject the disease must occur

The suspected pathogen must be re-isolated from this host and be identical to the original state

39
Q

Modes of disease transmission

A

reservoirs

carrier

asymptomatic carrier

tranmission

contact transmission

Fomite or indirect contact transmission

vehicle transmission

airborne transmission

vector transmission

nosocomial infections

40
Q

Reservoirs

A

the place or host where a pathogen normally resides

non-living reservoir such as soil or water

living reservoir such as an animal (bubonic plague in fleas of rodetns)

41
Q

Carrier

A

an individual who can transmit a pathogen but may or may not display symptoms of the disease

same host can be the reservoir and the carrier

42
Q

Asymtomatic carrier

A

an individual who can transmit a pathogen but does not display symptoms of the disease

43
Q

Transmission

A

movement of the pathogen from reservoir to host or between hosts

successful entry of pathogen inot or onto a new host after transmission is infection

44
Q

Contact transmission

A
Host to host movement of the pathogen by physical contact between two hosts
Ex)
-touching
-sexual intercourse
-droplet sprays
-usually involves mucous membranes
45
Q

Fomite or indirect contact transmission

A

Fomite is an inanimate object

Fomite becomes contaminated with the pathogen from one host then another host is infected from the object

ex)
Doorknob, cellphone, cutlery, towels and bedding, surfaces such as bed railings in hospitals

46
Q

Vehicle Transmission

A

Vehicle = food and water

mostly gastrointestinal tract infections

also known as fecal-oral transmission

47
Q

Airborne transmission

A

large droplets of water do not remain airborne for long

Droup out onto surfaces and then are touched by a host -> indirect contact transmission

The smaller the droplet, the longer it remains airborne and the more likely it can penetrate the host respiratory tract

5um or greater fall out of the air quickly and particles smaller than 5um remain airborne almost indefinitely

particles up to 20um may flow with air currents, ex) air conditioning for a distance then fall out.

48
Q

Vector Transmission

A

Transmission of the pathogen by a living organism

mechanical transmission is transmission by a living organism without that organism being infected (flies)

Biological transmission is where the pathogen reproduced in the vector organism
ex) arthropods that bite = yellow fever and malaria in mosquitoes, lyme diseaase and ticks

49
Q

Amplification vector

A

pathogen reproduces within the vector

liek malaria

50
Q

Nosocomial infections

A

infections aquired in a heath care setting or through the delivery of health care (iatrogenic infection)

also called a Hospital aquired infection (HAI)

usually defined as infections aquired in a health care setting whihc manifest a cartain time after admission (24-72 hrs)

can be more serious than community aquired (CA) infections

antibiotic resistant bacterial infections

51
Q

how long does it take to classify an infection as a nosocomial infection

A

24-72 hrs

52
Q

Symptom

A

subjective changes or conditons reported by the patient

53
Q

signs

A

objective changes or measurements

can be observed/ measured by outside observer

54
Q

Disease syndrome

A

signs and symptoms plus laboratory tests

test = petri, antibodies, WBC count, Crp count etc…

55
Q

Incubation time

A

time between infection and the start of reportable/ definative symptoms or signs

hard to know in a patient, because its hard to tell what was the initiating event.

56
Q

Prodromal stage

A

indicaiton that a disease is present but without enough diagnosis signs and symptoms

fever, chills, myalgia, malaise

57
Q

Illness period

A

Definite, diagnostic signs and symptonms, dieaase at its worst in the patient

58
Q

Convelecense

A

symptoms are mild but you are not back to 100%

this comes after the illness period

59
Q

Mortality rate

A

deaths/ population

need to use an adjusted mortality rate when comparing different countries (different people will die of different things at different ages)

60
Q

Crude mortality rate

A

deaths/ population/ year

61
Q

Top causes of mortality in Canada (2005)

/100 000

A

CVD 31%

Malignant neoplasms (cancer) 29%

Chronic respiratory diseases (also includes non-infections agents like asthma or emphesima) ~5%

Accidents 4.1%

diabetes

liver and kidney diseases

alzhiemers

Pregnancy, childbirth and perinatal

intential self-harm

influenza and pneumonia 2.5%

Tuberculosis

62
Q

TOp causes of mortality in Canada due to infectious agents

A

Septicaemia// Septic shock

Intestinal infections (rotavirus, e. coli, salmonella, shingella etc…)

HIV

Hepatitis

other infectious and parasitic diseases (malaria and others)

63
Q

Who regions

A

Americas

Western Pacific

Eastern mediterranean

South-east asia

europe

africa

64
Q

The three main causes of death

A

CVD 1/3
Cancer 1/3
Everything else 1/3

65
Q

children and young people die of

A

infectious diseases

66
Q

the elderly die of

A

degenerative diseases