Introduction to Epidemiological Methods

1
Introduction to Epidemiological Methods

• Bioterrorism Epidemiology
• Module 4
• Missouri Department of Health
• And Senior Services

2
Learning Objectives

• Define bioterrorism epidemiology
• Describe epidemiological approach to
  understanding disease etiology
• Recognize difference between incidence and
  prevalence
• Distinguish between the stages of the disease
  process

3
Biological and Chemical Epidemiology

• The study of the distribution and determinants of
  diseases resulting from a biological or chemical
  attack

4
Sources of Epidemiologic Clues to a Disease
Outbreak

• Clinicians office or medical clinic
• Emergency room
• Laboratory
• Veterinary Clinic
• Pharmacy

5
Epidemiologic Approach to Understanding Disease
Etiology

• Descriptive epidemiology - identifying
  associations of disease in relation to
• Time
• Place
• Persons

6
Epidemiologic Approach to Understanding Disease
Etiology

• Analytic epidemiology
• Identify associations of disease with possible
  etiologic factors (chemical release, biological
  agent)
• Further refine and test hypotheses regarding
  etiology

7
Problems Investigating the Causes of Disease

• Specific agent might not be known
• Location of agent release might not be known
• Signs and symptoms might not differentiate
  disease
• More than one agent might be used
• Time of agent release might not be known
• Latency period might not be known
• Latency is not the same for all people

8
Epidemiologic Triad of Disease
Host
Environment
Agent
9
Epidemiologic Triad of Disease
Host
Environment
Agent
10
Epidemiologic Triad of Disease
Host
Environment
Agent
11
Epidemiologic Triad of Disease
Host
Environment
Agent
12
Modes of Transmission

• Direct
• Contact
• Droplets
• Indirect
• Airborne
• Vehicle-borne
• Vector-borne
• Mechanical
• Biologic

Host
Environment
Agent
13
Modes of Transmission

• Direct
• Contact
• Droplets
• Indirect
• Airborne
• Vehicle-borne
• Vector-borne

Host
Environment
Agent
14
Factors That May Be Associated With Disease
Host Characteristics Types of Agents and Examples Environmental Factors
Age Sex Race Religion Customs Occupation Genetic profile Marital status Immune status Vaccination status Biologic (bacteria, viruses, toxin) Chemical (nerve, blister) Nuclear Bombs and flammables Temperature Humidity Altitude Wind Crowding
15
Factors That May Be Associated With Disease
Host Characteristics Types of Agents and Examples Environmental Factors
Age Sex Race Religion Customs Occupation Genetic profile Marital status Immune status Vaccination status Biologic (bacteria, viruses, toxin) Chemical (nerve, blister) Nuclear Bombs and flammables Temperature Humidity Altitude Wind Crowding
16
Factors That May Be Associated With Disease
Host Characteristics Types of Agents and Examples Environmental Factors
Age Sex Race Religion Customs Occupation Genetic profile Marital status Immune status Vaccination status Biologic (bacteria, viruses, toxin) Chemical (nerve, blister) Nuclear Bombs and flammables Location of Release Temperature Humidity Altitude Wind Crowding
17
Factors That May Be Associated With Disease
Host Characteristics Types of Agents and Examples Environmental Factors
Age Sex Race Religion Customs Occupation Genetic profile Marital status Immune status Vaccination status Biologic (bacteria, viruses, toxin) Chemical (nerve, blister) Nuclear Bombs and flammables Location of Release Temperature Humidity Altitude Wind Crowding
18
Factors That May Be Associated With Disease
Host Characteristics Types of Agents and Examples Environmental Factors
Age Sex Race Religion Customs Occupation Genetic profile Marital status Immune status Vaccination status Biologic (bacteria, viruses, toxin) Chemical (nerve, blister) Nuclear Bombs and flammables Location of Release Temperature Humidity Altitude Wind Crowding
19
Factors That May Be Associated With Disease
Host Characteristics Types of Agents and Examples Environmental Factors
Age Sex Race Religion Customs Occupation Genetic profile Marital status Immune status Vaccination status Biologic (bacteria, viruses, toxin) Chemical (nerve, blister) Nuclear Bombs and flammables Location of Release Temperature Humidity Altitude Wind Crowding
20
Factors That May Be Associated With Disease
Host Characteristics Types of Agents and Examples Environmental Factors
Age Sex Race Religion Customs Occupation Genetic profile Marital status Immune status Vaccination status Biologic (bacteria, viruses, toxin) Chemical (nerve, blister) Nuclear Bombs and flammables Location of Release Temperature Humidity Altitude Wind Crowding
21
Factors That May Be Associated With Disease
Host Characteristics Types of Agents and Examples Environmental Factors
Age Sex Race Religion Customs Occupation Genetic profile Marital status Immune status Vaccination status Biologic (bacteria, viruses, toxin) Chemical (nerve, blister) Nuclear Bombs and flammables Location of Release Temperature Humidity Altitude Wind Crowding
22
Factors That May Be Associated With Disease
Host Characteristics Types of Agents and Examples Environmental Factors
Age Sex Race Religion Customs Occupation Genetic profile Marital status Immune status Vaccination status Biologic (bacteria, viruses, toxin) Chemical (nerve, blister) Nuclear Bombs and flammables Location of Release Temperature Humidity Altitude Wind Crowding
23
Factors That May Be Associated With Disease
Host Characteristics Types of Agents and Examples Environmental Factors
Age Sex Race Religion Customs Occupation Genetic profile Marital status Immune status Vaccination status Biologic (bacteria, viruses, toxin) Chemical (nerve, blister) Nuclear Bombs and flammables Location of Release Temperature Humidity Altitude Wind Crowding
24
Factors That May Be Associated With Disease
Host Characteristics Types of Agents and Examples Environmental Factors
Age Sex Race Religion Customs Occupation Genetic profile Marital status Immune status Vaccination status Biologic (bacteria, viruses, toxin) Chemical (nerve, blister) Nuclear Bombs and flammables Location of Release Temperature Humidity Altitude Wind Crowding
25
Numerators and Denominators
26
What Is a Numerator

• Count of cases

27
What Is a Numerator

• Count of cases
• Frequently organized in a line-listing

28
Line Listing
29
What Is a Numerator

• Count of cases
• Frequently organized in a line-listing
• Allows for regrouping and counting cases by their
  various characteristics

30
What Is a Numerator

• Count of cases
• Frequently organized in a line-listing
• Allows for regrouping and counting cases by their
  various characteristics
• Might be incident or prevalence cases

31
Incidence and Prevalence
Incidence
32
Incidence and Prevalence
Number of new cases of a disease over a period of
time
Incidence
33
Incidence and Prevalence
Prevalence
34
Incidence and Prevalence
Total number of cases of a disease
Prevalence
35
Relationship Between Incidence and Prevalence
Recovery
Death
Incidence
Prevalence Pot
36
Relationship Between Incidence and Prevalence
Recovery
Death
Incidence
Prevalence Pot
37
Relationship Between Incidence and Prevalence
Recovery
Death
Incidence
Prevalence Pot
38
Relationship Between Incidence and Prevalence
Recovery
Death
Incidence
Prevalence Pot
39
Relationship Between Incidence and Prevalence
Recovery
Death
Incidence
Prevalence Pot
40
Relationship Between Incidence and Prevalence
Recovery
Death
Incidence
Prevalence Pot
41
Relationship Between Incidence and Prevalence
Recovery
Death
Incidence
Prevalence Pot
42
Relationship Between Incidence and Prevalence
Recovery
Death
Incidence
Prevalence Pot
43
Relationship Between Incidence and Prevalence
Recovery
Death
Incidence
Prevalence Pot
44
Relationship Between Incidence and Prevalence

• Under the assumption of a steady-state
• Prevalence I D
• I incidence
• D duration

Recovery
Death
Incidence
Prevalence Pot
45
Relationship Between Incidence and Prevalence

• Under the assumption of a steady-state
• Prevalence I D
• I incidence
• D duration

Recovery
Death
Incidence
Prevalence Pot
46
Relationship Between Incidence and Prevalence

• Under the assumption of a steady-state
• Prevalence I D
• I incidence
• D duration

Recovery
Death
Incidence
Prevalence Pot
47
Episodes of Tularemia
Number of Persons
M
L
K
J
I
H
G
F
D
E
C
B
A
TIME
48
Episodes of Tularemia
Number of Persons
M
L
K
J
I
H
G
F
D
E
C
B
A
TIME
49
Episodes of Tularemia
Number of Persons
M
L
K
J
I
H
G
F
D
E
C
B
A
TIME
50
Episodes of Tularemia
Number of Persons
M
L
K
J
I
H
G
F
D
E
C
B
A
TIME
51
Episodes of Tularemia
Number of Persons
M
L
K
J
I
H
G
F
D
E
C
B
A
TIME
52
Episodes of Tularemia
Number of Persons
M
L
K
J
I
H
G
F
D
E
C
B
A
TIME
53
Episodes of Tularemia
Number of Persons
M
L
K
J
I
H
G
F
D
E
C
B
A
TIME
54
What is the prevalence of tularemia on July 1998
in these 20 people?
Number of Persons
M
L
K
J
I
H
G
F
D
E
C
B
A
TIME
55
What is the prevalence of tularemia on July 1998
in these 20 people?
Number of Persons
M
L
K
J
I
H
G
F
D
E
C
B
A
TIME
56
The Natural History of Disease
Outcome Cure Control Disability Death
Healthy
Disease Symptoms Seek Diagnosis
Treatment Onset Care
57
The Natural History of Disease
Outcome Cure Control Disability Death
Healthy
Disease Symptoms Seek Diagnosis
Treatment Onset Care
58
The Natural History of Disease
Outcome Cure Control Disability Death
Healthy
Disease Symptoms Seek Diagnosis
Treatment Onset Care
59
The Natural History of Disease
Outcome Cure Control Disability Death
Healthy
Disease Symptoms Seek Diagnosis
Treatment Onset Care
60
The Natural History of Disease
Outcome Cure Control Disability Death
Healthy
Disease Symptoms Seek Diagnosis
Treatment Onset Care
61
The Natural History of Disease
Outcome Cure Control Disability Death
Healthy
Disease Symptoms Seek Diagnosis
Treatment Onset Care