MIDTERM Flashcards
(139 cards)
1
Q
Define
What is epidemiology?
Lecture 1
A
the study of the distribution and determinants of health-related states or events among specific populations and the application of the study to the control of health problems
2
Q
Epidemiology: True or False
Epidemiology is often described as the basic science of public health.
A
True
3
Q
Epidemiology
What is distribution?
Lecture 1
A
frequency + pattern
- in other words: “how many people?” + “where?”
4
Q
Epidemiology: Distribution
Define frequency
Lecture 1
A
- the number of health-related events
- how often these events occur compared to the total number of people in the population
5
Q
Epidemiology: Distribution
Define pattern
Lecture 1
A
- occurrence of health-related events by time, place, and person
- time may be: annual, seasonal, weekly, daily, hourly, weekday vs weekend, etc.
- place includes: geographic variation, urban/rural differences, location of work sites or schools
- personal characteristics include: age, sex, marital status, SES, behaviors, and environmental exposures
6
Q
Epidemiology
What are determinants?
Lecture 1
A
the causes and other factors that influence the occurrence of disease and other health-related events
7
Q
Specified Populations
Epidemiologist vs. Physicians
Lecture 1
A
Epidemiologist:
- concerned about the health of the overall population
Physicians:
- concerned about the health of an individual
clinician’s patient is indiviual; epidemiologist’s patient is community
8
Q
Epidemiology
What is the application of epidemiology?
Lecture 1
A
it involves applying the knowledge gained by the studies to community-based practice b/c the goal is to prevent disease in the community
9
Q
John Snow
Who is John Snow?
Lecture 2
A
An anesthesiologist in the mid 1800s who conducted a series of investigations in London.
- conducted studies of cholera outbreak to discover the cause of disease and how to prevent its recurrence
10
Q
John Snow: True or False
The father of epidemiology is John Graunt.
Lecture 2
A
False
11
Q
John Snow
Breakdown and explain Snow’s first investigation
Broad Sreet Pump
Lecture 2
A
- A severe cholera epidemic occurred / outbreak
- Snow created a spot map, marking where cholera cases occurred and the locations of water pumps
- He observed patterns and noticed most cases clustered around the Broad Street pump (Pump A)
- Then, he gathered community insights and found out that residents avoided Pump B because it was contaminated and Pump C because it was inconvenient
- To confirm his findings, he investigated anomalies and found that workers at a nearby brewery who drank from a private well did not get cholera and gathered infromation on where people with cholera obtained their water
- Snow formed his hypothesis and conclued that contaminated water from the Broad Street pump was likely the source of the outbreak
- Lastly, he took action by presenting his information to officials and got the pump handle removed
12
Q
Epidemiology - John Snow
What is descriptive epidemiology?
Lecture 2
A
describing a health related event in terms of person, place, and time
13
Q
Epidemiology - John Snow
What is analytic epidemiology?
Lecture 2
A
measures the association between an exposure and disease
14
Q
John Snow
What does Snow’s research demonstrate
Lecture 2
A
- descriptive epidemiology
- hypothesis generation
- hypothesis testing / analytical epidemiology
- application
15
Q
Epidemiology: Uses
What are the 4 diff uses of epidemiology?
Lecture 2
A
- Assessing the community’s health
- Making individual decisions
- Completing the clinical picture
- Searching for causes
16
Q
Epidemiology: Uses
Assessing the community’s health
Explain
Lecture 2
A
use of data to set goals and monitor progress towards them
- need relevant sources of data
ex: Healthy People 2030
17
Q
Epidemiology: Uses
Making individual decisions
Explain
Lecture 2
A
use of epidemiologic information to make daily decisions about health
18
Q
Epidemiology: Uses
Completing the clinical picture
Explain
Lecture 2
A
epidemiologists assist physicians in properly diagnosing illness
19
Q
Epidemiology: Uses
Searching for causes
Explain
Lecture 2
A
provides substantial evidence to link exposure and illness and effect action
in other words: why did this disease happen
20
Q
Epidemiology: Core Functions
What are the 6 core functions of epidemiology?
Explain
Lecture 2
A
- public health surveillance
- field investigations
- analytic studies
- evaluation
- linkages
- policy development
21
Q
Epidemiology: Core Functions
Public health surveillance
Explain
Lecture 2
A
ongoing, systemic collection of data to guide decision making and action
goal: to portray patterns of disease to control spread and implement prevention measures
how: morbidity and mortality reports
22
Q
Public Health Surveillance
What is the difference between active and passive surveillance?
A
- active: surveillance is on public officials
- passive: other entities report the data
23
Q
Epidemiology: Core Functions
Field Investigation
Explain
Lecture 2
A
the process of collecting and analyzing data directly in affected areas to find the source and spread of a disease
also referred to as “shoe leather epidemiology”
24
Q
Epidemiology: Core Functions
Analytic studies
Explain
Lecture 2
A
evaluate the credibility of a hypothesis generated from surveillance and field invetigation
25
# Epidemiology: Core Functions
Evaluation
| Explain
## Footnote
Lecture 2
determmine relevance, effectiveness, efficiency, and impact in relation to goals
26
# Epidemiology: Core Functions
Linkages
| Explain
## Footnote
Lecture 2
connecting public health agencies, laboratories, and healthcare providers to share information and collaborate on disease prevention and response, etc.
27
# Epidemiology: Core Functions
Policy Development
| Explain
## Footnote
Lecture 2
creating and implementing public health policies based on data and research to protect and improve community health
28
# Epidemiologic Approach
What does an epidemiologist do?
## Footnote
Lecture 3
- **Counts** cases or health events, and describes them in terms of time, place, and person
- **Divides** the number of cases by an appropiate denominator to calculate rates
- **Compares** these rates over time or for different groups of people
29
# Epidemiologic Approach
Define rate
## Footnote
Lecture 3
the number of cases divided by the size of the population per unit of time
30
# Case definition
What is a case definition?
## Footnote
Lecture 3
a set of standard criteria for classifying whether a person has a particular disease, syndrome or other health condition
31
# Case definition
What are the components of a case defintion?
## Footnote
Lecture 3
- lab tests
- signs (objective)
- symptoms
- time, place, and/or person (outbreak investigations)
32
# True or False
Case definitions are set and do not change.
## Footnote
Lecture 3
**False**
case definitions **may** change over time as more information is obtained
33
# Case definition
What are the different types of case definitions?
## Footnote
Lecture 3
**sensitive**: broad or loose
goal = to capture all true cases
**strict**: specific
goal = ensure an individual is truly a case
34
# True or False
ALL case definitions require laboratory confirmation
## Footnote
Lecture 3
**False**
some disease have no distinctive laboratory findings
35
# Epidemiology
What are the 5 W's of epidemiology?
## Footnote
Lecture 3
- **what** (health issue of concern)
- **who** (person)
- **where** (place)
- **when** (time)
- **why/how** (why is this disease occurring and how is it spreading)
36
# Epidemiology
What are the different ways to compile data by time?
## Footnote
Lecture 3
- secular trends (overtime/long term)
- seasonally
- days of the week/time of the day
- epidemic period
37
# Epidemiology
What are the different ways to compile data by geographic extent?
## Footnote
Lecture 3
unit:
- large (continent)
- small (hospital wing)
categorical:
- urban
- rural
state
38
# Epidemiology
What is used to compile data when it comes to people?
## Footnote
Lecture 3
- sex
- ethnicity
- SES
- age
- occupation
- leisure activity
- behaviors
- use of medication
39
# Epidemiology
What is the most important person attribute when compiling data according to the textbook?
## Footnote
Lecture 3
age
40
# Analytic Epidemiology
What is the key feature of analytic epidemiology?
## Footnote
Lecture 3
comparison group
41
# Analytic Epidemiology
What are the two categories of studies that fall under analytic epidemiology?
## Footnote
Lecture 3
- experimental
- observational
42
# Analytic Epidemiology
What are the functions of an experimental study?
## Footnote
Lecture 3
- controlled process determines the **exposure for participants**
- tracking over time determines the **effects of the exposure**
| ex: placebo
43
# Analytic Epidemiology
What is the function of observational studies?
## Footnote
Lecture 3
to observe the exposure or disease status in participants
44
# Analytic Epidemiology: Observational Studies
What are the 3 types of observational studies?
## Footnote
Lecture 3
- cohort (prospective)
- case control
- cross sectional
45
# Analytic Epidemiology
What are the features of a cohort study?
## Footnote
Lecture 3
- **start with exposed individuals** (we know the exposure)
- follow individual to see if they develop disease of interest
46
# Analytic Epidemiology
What are the features of a case-control study?
## Footnote
Lecture 3
- investigators enroll a group of participants with a disease (case-patients)
- **starts with ill individuals** (we are looking for the exposure)
- control group provides an estimate of the baseline or expected amount of exposure in the population
47
# Analytic Epidemiology
What are the features of a cross-sectional study?
## Footnote
Lecture 3
- weakest study because it lacks time aspect but gets a quick idea
- exposures and health statuses of sample population are measured simultaneously
- assesses the prevelance of a health outcome at that point in time without regard to duration
- **exposure and outcome are measured at the same time**
48
# Analytic Epidemiology
Overall summary
## Footnote
lecture 3
cohort: starts with **exposed** individuals
case control: starts with **ill** individuals (back tracking and seeing what exposure led to them being sick)
cross section: measures exposure and disease at the same time
49
# Models of Disease Causation
What are the 3 models of disease causation discussed?
## Footnote
lecture 4
- Rothman's Pie
- Chain of Infection
- Epidemiologic Triad/Triangle (simplest)
50
# Models of Disease Causation
What does the Epidemiologic Triad consist of?
## Footnote
lecture 4
agent, host, environment
51
# Concepts of Disease Occurrence
Agent
## Footnote
lecture 4
infectious microorganism or pathogen
- virus, bacterium, parasite, or other microbe
- chemical contaminants or physical causes of disease or injury
*generally:* agent must be present for disease to occur
52
# Concepts of Disease Occurrence
Host
## Footnote
lecture 4
the human who can get the diease
- dependent upon susceptibility, response to an agent
53
# Concepts of Disease Occurrence
Environment
## Footnote
lecture 4
extrinsic factors that affect the agent and the opportunity for exposure
- geology
- climate
- insects transmitting the agent
- socioeconmic factors
54
# Models of Disease Causation
Rothman's Pie
## Footnote
lecture 4
all pieces of the pie fall into place = disease occurs
- **component causes**: individual factors (one piece)
- **sufficient causes**: complete pie (if more pieces come together
- **necessary causes**: component that occurs in every disease pie (most usually its the bacteria)
55
# Concepts of Disease Occurrence
Natural history
| define
## Footnote
lecture 4
the progression of disease in an individual over time in the absence of treatment
*timeline could be years*
56
# Concepts of Disease Occurrence
Spectrum of disease
| define
## Footnote
lecture 4
the range of manifestations and severities of illness associated with given dieases, illness or injury
57
# Infectious Agents
What are the terms for infectious agents?
## Footnote
lecture 4
**infectivity:** proportion of exposed persons who become *infected*
**pathogenicity:** proportion of infected individuals who develop *clincally apparent disease*
**virulence:** the proportion of clinically apparent cases that are *severe or fatal*
58
# Natural History Timeline
What is the timeline for disease?
## Footnote
lecture 4
1. **stage of susceptibility** (exposure occurs)
2. **stage of subclinical disease** (where pathologic changes occur but individual does not know they are sick; asymptomatic)
*in between:* onset of symptoms and usual time of diagnosis
3. **stage of clinical disease** (symptoms present and individual knows they are sick)
4. **stage of recovery, disability or death**
***infectious disease*: incubation period**
***chronic disease*: latency period**
59
# Chain of infection
What is the chain of transmission?
## Footnote
lecture 4
transmission occurs when the agent **leaves its *reservoir*** or host **through a *portal of exit*,** is **conveyed by some *mode of transmission*** and **enters through a *portal of entry* to infect** a susceptible *host*
60
# Portal of Exit
What is portal of exit?
## Footnote
lecture 4
how the pathogen leaves its host
| corresponds to the site where the pathogen is localized
61
# Modes of Transmission
What are the two modes of transmission?
| define
## Footnote
lecture 4
**direct:**
- direct contact (mono)
- droplet spread (sneezing, coughing, etc.)
**indirect:**
- airbone (infectious agents carried by dust or droplet nuclei suspended in the air; ex: measles)
- vehicle (food, water, biologic products)
- vector (mosquitoes, fleas, ticks, etc.)
62
# Modes of Transmission
Define airbone
## Footnote
lecture 4
infectious agents carried by dust or droplet nuclei suspended in the air
63
# Modes of Transmission
Define vehicle
## Footnote
lecture 4
food, water, biologic products (blood), etc
64
# Modes of Transmission
Define vector
## Footnote
lecture 4
mosquitoes, fleas, ticks, etc.
65
# Portal of Entry
What is portal of entry?
## Footnote
lecture 4
how a pathogen enters a susceptible host
ex: skin, mucous membrane, blood
66
# Disease Control - Chain of Infection
How do we **eliminate the agent**?
| EXAMPLE
## Footnote
lecture 4
antibiotics
67
# Disease Control - Chain of Infection
What methods can help to control the **mode of transmission** of a disease?
| EXAMPLE
## Footnote
lecture 4
- isolation/quarantine
- elimination of the vehicle
68
# Disease Control - Chain of Infection
How can we protect **portals of entry**?
| EXAMPLE
## Footnote
lecture 4
- bed nets
- masks, gloves
69
# Disease Control - Chain of Infection
How can we increase a **host's defense**?
| EXAMPLE
## Footnote
lecture 4
vaccination
70
How does the host susceptibility vary?
## Footnote
lecture 4
- genetics differ
- immune/resistant to disease
- lifestyle factors
| etc.
71
# Implications for Public Health
What are interventions directed at?
## Footnote
lecture 4
- controlling or eliminating agent
- interrupting the mode of transmission
- protecting portals of entry
- increasing a host's defenses
72
# Level of Disease
What levels of disease are there?
## Footnote
lecture 4
- sporadic
- endemic
- hyperendemic
- epidemic
- outbreak
- cluster
- pandemic
73
# Level of Disease
Define sporadic
## Footnote
Lecture 4
disease that occurs infrequency/irregularly
- uncommon
- random
- one case/first case
74
# Level of Disease
Define endemic
## Footnote
Lecture 4
amount of disease usually present in a community
- typical cold or flu
- we expect this, its our usual
75
# Level of Disease
Define hyperendemic
## Footnote
Lecture 4
persistent, **high** levels of disease
- regularly
76
# Level of Disease
Define epidemic
## Footnote
Lecture 4
often sudden increase of cases
77
# Level of Disease
Define outbreak
## Footnote
Lecture 4
often sudden increase of cases ***in a more limited geographic location***
- ex: on stony brook campus vs in state of NY
78
# Level of Disease
Define cluster
## Footnote
Lecture 4
aggregation of cases **grouped in place and time** suspected to be greated than the number expected
- don't know why
- unrelated
79
# Level of Disease
Define pandemic
## Footnote
Lecture 4
epidemic spread **over several countries or continents**
80
# Levels of Disease - Epidemic
Why do epidemics occur?
## Footnote
lecture 4
- agent and host present inadequate numbers
- increase in amount of virulence of agent
- introduction of agent in a setting it has never been before
- enhanced mode of transmission
- change in susceptibility of hosts
- new portals of entry
81
# Epidemic Patterns
What are the type of patterns used to classify epidemics?
| **classified according to their manner of spread through a population**
## Footnote
lecture 4
- common source
- propagated
- mixed
82
# Epidemic Patterns
Define common source
## Footnote
lecture 4
group of persons are all exposed to an infectious agent or a toxin ***from the same source***
**point source:** group exposed over a relatively brief period (*becoming sick in the same incubation period*)
**continous common source:** case-patients exposed over days, weeks, or longer
**intermittent common source:** irregular pattern of exposure (*still from the same source*)
83
# Epidemic Patterns
Define propagated
## Footnote
lecture 4
transmission **from one person to another**; cases occur over *more than one incubation period*
- direct person-to-person
- vehicle or vectorborne
84
# Organizing Data: Line Listing
What is line listing used for?
## Footnote
lecture 5
used in routine surveillance, investigating an outbreak, conducting a study, etc. **to compile information in an organized manner**
| *organized like a spreadsheet with rows and columns*
85
# Organizing Data: Line Listing
What makes up a line listing?
## Footnote
lecture 5
**row**: called a record or observation
- represents one person or case of disease
**column**: called a variable
- contains information about one characteristic of the individuals (race or date of birth)
86
# Organizing Data: Line Listing
What is a value?
## Footnote
lecture 5
value of a variable is the number or descriptor that applies to a particular person (5'6", female, never vaccinated, etc.)
- the type of values influence the way in which the variables can be summarized
| *can be numeric but also can be descriptive* + there are four types
87
# Organizing Data: Line Listing
What are the four types of variables?
## Footnote
lecture 5
- **nominal**-scale variable
- **ordinal**-scale variable
- **interval**-scale variable
- **ratio**-scale variable
88
# Organizing Data: Types of variables
nominal
| define
## Footnote
lecture 5
values are categorized *without* numerical ranking
(ex: ill or well, dead or alive)
89
# Organizing Data: Types of variables
ordinal
| define
## Footnote
lecture 5
values are ranked but not necessarily evenly spaced
(ex: stages of breast cancer)
90
# Organizing Data: Types of variables
interval
| define
## Footnote
lecture 5
measured on a scale of equally spaced units but *without a true zero point* (ex: shoe sizes, test scores)
91
# Organizing Data: Types of variables
ratio
| define
## Footnote
lecture 5
an interval variable ***with a true zero*** (ex: height, age, sickness duration)
92
# Organizing Data: Line Listing
Which variables of the 4 are qualitative variables?
| *also known as categorical*
## Footnote
lecture 5
nominal and ordinal
93
# Organizing Data: Frequency Distribution
Which variables of the 4 are quantitative variables?
| *also known as continuous*
## Footnote
lecture 5
interval and ratio
94
# Frequency Distributions
What is a frequency distribution?
## Footnote
lecture 5
a table or graph that shows how often different values or group of values appear in a dataset
*in public health terms:* a way of organizing and presenting health related data to show how often a particular health condition, behavior, or characteristic occurs in a population
- **helps identify trends, risk factors, and disparities in health outcomes**
95
# Frequency Distributions
What are the features/properties of frequency distributions?
## Footnote
lecture 5
- **central location**
- **spread**
- **shape**
- **range**
96
# Frequency Distributions
What is the Gaussian distribution?
| also known as normal distribution
## Footnote
lecture 5
the classic symmetrical bell-shaped curve
- no skew
97
spread
## Footnote
lecture 5
how widely dispersed a graph is
98
shape
## Footnote
lecture 5
symmetry
*can be symmetrical or asymmetrical (skewed)*
99
# Shape: Skewness
positive skew
| define
central location is to the left of the tail **(tail points to the right)**
100
# Shape: Skewness
negative skew
| define
central location is to the right of the tail **(tail points to the left)**
101
range
## Footnote
lecture 5
measured by spread and distribution
102
# Frequency Distributions: Properties
central location
| define
## Footnote
lecture 5
where the graph peaks
there are three measures of central location used in epidemiology: **mean, median, and mode**
103
# Central Location: Types of Measures
mean
## Footnote
lecture 5
the average value (add up all the numbers and divide by the amount of numbers that are present)
*use:*
- has excellent statistical properties; commonly used in statistical manipulations and analyses
- called the center of gravity
- affected by any extreme value
104
# Central Location: Types of Measures
median
## Footnote
lecture 5
number in the middle (after being numerically ordered)
*use:*
- good descriptive measure
- relatively easy to identify
- not often used in statistical manipulations and analyses
- not generally affected by extreme values
105
# Central Location: Types of Measures
mode
## Footnote
lecture 5
number that shows up the most
*use:*
- preferred measure of central location
- can have one or two more
- used almost exclusively as a descriptive measure
- not affected by extreme values
106
# Investigating an Outbreak
Why would we investigate an outbreak?
## Footnote
lecture 6
- **control or prevention of the health problem**
- opportunity to learn / research
- public, political, or legal concerns
- public health program considerations
- training
| the most important reason is for control and prevention
107
# Investigating an Outbreak
What are the steps of an outbreak investigation?
## Footnote
lecture 6
1. prepare for field work
2. establish the existence of an outbreak
3. verify the diagnosis
4. contruct a working case definition
5. find cases systemically and record information
6. perform descriptive epidemiology
7. develop hypotheses
8. evaluate hypotheses epidemiologically
9. reconsider, refine, re-evaluate
10. compare with lab and/or environment studies
11. implement control and prevention measures
12. initiate or maintain surveillance
13. communicate findings
108
# Investigating an Outbreak: Steps (1)
Prepare for field work
| define
## Footnote
lecture 6
officials discover an increase in the number of cases of a particular disease and then decide that a field investigation is warranted
- **scientific and investigate issues:** must have the appropiate scientific knowledge, supplies, and equipment
- review applicable literature
- assemble useful references (jounrnal articles, sample questionnares)
- know what supplies/equipment to protect yourself
- have a plan of action
- **management and operational issues:** must be a good manager and collaborator because most investigations are conducted by a team rather than just one individual
- roles and responsibilities for each members
- communications plan to know how often and when to calls with involved agencies, etc.
- arrange travel, lodging and local transportation
109
# Investigating an Outbreak: Steps (2)
Establish the existence of an outbreak
| define
## Footnote
lecture 6
verify that the cases are in fact an outbreak; observed cases compared to the number of expected cases
- **outbreak or an epidemic:** the occurrence of more cases of disease than expected in a given area or among a specific group of people over a particular period of time
110
# Investigating an Outbreak: Steps (3)
Verify the diagnosis
| define
## Footnote
lecture 6
important because you must ensure that the disease has been properly identified since control measures are often disease specific and to rule out laboratory error as the basis for the increase in reported cases
- **review clinical findings and lab results**
- **visit one or more patients with the disease to get a better understanding of clinical features**
*Helps with generating a hypotheses about disease spread*
| just like John Snow did with his investigation
111
# Investigating an Outbreak: Steps (4)
Construct a working case defintion
| define
## Footnote
lecture 6
includes clinical criteria, and may be restricted by time, place, and person
- diagnosis may be uncertain early on in an investigation. so, **cases will be classified as suspected, probable, and confirmed**
112
# Investigating an Outbreak: Steps (5)
Find cases & record information
| define
## Footnote
lecture 6
public health workers must look for additional cases to determine the true geographic extent of the problem and the populations affected by it
- **passive surveillance:** sending a letter describing the situation and asking for reports of similar cases (*other entities report the data)*
- **active surveillance:** telephoning or visiting the facilities *by self* to collect information on any additional cases
***following data is collected:***
- identifying information
- demographic information
- clinical information
- risk factor information
- reporter information (source of the report)
113
# Investigating an Outbreak: Steps (6)
Perform descriptive epidemiology
| define
## Footnote
lecture 6
summarizing by time, place, and person
- provides a comprehensive characterization of the outbreak
- infer the population at risk for disease
- provides clues about source, modes of transmission, etc.
- begin thinking about where to begin intervention
**helps formulate hypotheses**
114
# Investigating an Outbreak: Steps (7)
Develop hypotheses
| define
## Footnote
lecture 6
- if the epidemic curve points to a narrow period of exposure, *what events occurred around that time*?
- why do these people living in one particular area have the highest rate of disease
- why are some groups at greater risk than others?
**answers to these questions assist epidemiogists in formulating their hypothesis**
115
# Investigating an Outbreak: Steps (8)
Evaluate hypotheses
| define
## Footnote
lecture 6
2 ways:
1. compare hypothesis to established facts
2. use analytic epidemiology to quantify relationships:
- *retrospective cohort/risk ratio*
- *case-cohort/odds ratio*
116
# Analytic Evaluation (Step 8)
What does a retrospective cohort study consist of?
## Footnote
lecture 6
- small, *well-defined population*
- **exposure and outcomes have already occurred**
- calculate the attack rate for those exposed to those not exposed
- **calculate risk ratio**
117
# Analytic Evaluation (Step 8)
How do you calculate the attack rate?
## Footnote
lecture 6
attack rate = those **sick** who were exposed/**ALL** exposed
attack rate = those **sick** who were not exposed/**ALL** unexposed
*high attack rate among those exposed and low attack rate among those **not** exposed = **exposure is a strong suspect***
118
# Analytic Evaluation (Step 8)
What is the method for calculating risk ratio?
## Footnote
lecture 6
attack rate in **exposed** group/attack rate in **unexposed** group
119
# Analytic Evaluation (Step 8)
What does a case-cohort consist of?
## Footnote
lecture 6
investigator asks case-patients and **controls** about their exposures and conducts an **odds ratio** to quantify the relationship between *exposure and disease*
**controls *need* to be identified in this study**
120
# Analytic Evaluation (Step 8)
What is the method for calculating the odds ratio?
## Footnote
lecture 6
(number of exposed *cases* **x** number of unexposed *controls*) **/** (number of exposed *controls* **x** number of unexposed *cases*)
**or**
(AxD)/(BxC)
121
# Investigating an Outbreak: Steps (9)
Reconsider, refine, re-evaluate
| define
## Footnote
lecture 6
done in the case that analytic studies do not provide adequate insight
122
# Investigating an Outbreak: Steps (10)
Compare - lab & environmental
| define
## Footnote
lecture 6
laboratory evidence can **confirm the findings**
environmental studies can **explain why an outbreak occurred**
123
# Investigating an Outbreak: Steps (11)
Control & prevention
| define
## Footnote
lecture 6
*primary goal:* to **control** outbreak AND **prevent** additional cases
control measure are usally aimed at segments of the **chain of transmission (agent, host, mode of transmission, portal of entry)**
124
# Investigating an Outbreak: Steps (12)
Initiate / maintain surveillance
| define
## Footnote
lecture 6
once control and prevention measures are implemented, they must be **monitored**
- this usually comes in the form of **active surveillance**
*questions epidemiologists ask:*
- are new cases slowing down or stopping
- are new cases continuing to occur
- where are the new cases, if any
- has the outbreak spread outside the original area where interventions were targeted
125
# Investigating an Outbreak: Steps (13)
Communicate findings
| define
## Footnote
lecture 6
**oral briefing for local authorities**
- in attendance: local health authorities, those responsible for implementing control and prevention measures (epidemiologists)
- investigator describes what they found and recommendations for action
**written report**
- the usual format (intro, background, methods, etc...)
- this may serve as a reference for health departments encountering a similar outbreak in the future
126
# Measures of RIsk
What is a frequency measure?
## Footnote
lecture 7
characterizes only one **part of the distribution** to another part of the distribution
consists of: **ratios, proportions and rates**
127
# Frequency Measures
What is a ratio?
## Footnote
lecture 7
a comparison of *any* two values
- will always have a fraction
- the numerator and denominator of a ratio **can be related** *or* **unrelated**
ex: you can be comparing apples to oranges
128
# Frequency Measures
What is a proportion?
## Footnote
lecture 7
comparison of a **part** to the ***whole***
- the numerator is *included* in the denominator
129
# Frequency Measures
What is a rate?
## Footnote
lecture 7
a measure of the frequency with which an event occurs in a **defined population** over a ***specified period of time***
- useful for comparing disease frequency in different locations, at different times or among different groups of people with potentially different sized populations
130
# Mortality Requency Measures
What is an infant mortality rate?
## Footnote
lecture 7
number of deaths among children less than one year old
- denominator = number of live births *during the same time period*
- most commonly used measure for comparing health status among nations
| very telling of a how well a country's population is doing
131
# Rates
Define incidence
## Footnote
lecture 7
occurence of **new cases of disease** in a population over a specified period of time
132
# Rates
What does incidence describe?
## Footnote
lecture 7
- the probability of developing the disease during a specific period
- describes how quickly a disease occurs in a population
133
Define prevelance
## Footnote
lecture 7
proportion of persons in a population who have a particular disease or attribute at a specified point in time or over a specificed point in time
- measure used for chronic disease rate
134
# Examples
What is the following fraction an example of:
**number of women who have breast cancer in NYS / number of women who have cervical cancer in NYS**
## Footnote
lecture 7
ratio
135
# Examples
What is the following ratio an example of:
**number of women who have breast cancer in NY / number of women who have any type of cancer in NY**
## Footnote
lecture 7
proportion
136
# Examples
What is the following fraction an example of:
**number of men who died from lung cancer in NYS in Feb 2025 / number of men living in NYS in Feb 2025**
## Footnote
lecture 7
rate
137
# Examples
What is the following fraction an example of:
**number of deaths among children less than 1 year of age reported during a given time period x 1,000 / number of *live births* reported during the same time period**
## Footnote
lecture 7
infant mortality rate
138
# Examples
What is the following fraction an example of:
**number of women newly diagnosed with heart disease in NYS in 2025 / number of women living in NYS in 2025**
## Footnote
lecture 7
incidence
| key word: newly
139
# Examples
What is the following an example of:
**number of women who have breast cancer in NYS / number of women living in NYS**
## Footnote
lecture 7
prevelance
| numerator incl. all cases present during given time period NOT JUST NEW
