Introduction to Epidemiological Methods by gregoria

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									    Introduction to
Epidemiological Methods

   Bioterrorism Epidemiology
            Module 4

   Missouri Department of Health
       And Senior Services
      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
   Biological and Chemical
        Epidemiology
The study of the distribution and
 determinants of diseases resulting from a
 biological or chemical attack
Sources of Epidemiologic Clues to
      a Disease Outbreak
  •   Clinician’s office or medical clinic
  •   Emergency room
  •   Laboratory
  •   Veterinary Clinic
  •   Pharmacy
 Epidemiologic Approach to
Understanding Disease Etiology
• Descriptive epidemiology - identifying
  associations of disease in relation to
  • Time
  • Place
  • Persons
 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
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
Epidemiologic Triad of Disease
            Host




   Agent             Environment
Epidemiologic Triad of Disease
            Host




   Agent             Environment
Epidemiologic Triad of Disease
             Host




   Agent             Environment
Epidemiologic Triad of Disease
             Host




   Agent              Environment
    Modes of Transmission
• Direct                    Host
  • Contact
  • Droplets
• Indirect
  • Airborne
  • Vehicle-borne   Agent          Environment

  • Vector-borne
     • Mechanical
     • Biologic
    Modes of Transmission
• Direct                    Host

  • Contact
  • Droplets
• Indirect
  • Airborne        Agent          Environment
  • Vehicle-borne
  • Vector-borne
               Factors That May Be
              Associated With Disease
  Host Characteristics        Types of Agents and Examples      Environmental Factors

Age                      Biologic (bacteria, viruses, toxin)   Temperature
Sex                      Chemical (nerve, blister)             Humidity
Race                     Nuclear                               Altitude
Religion                 Bombs and flammables                  Wind
Customs                                                        Crowding
Occupation
Genetic profile
Marital status
Immune status
Vaccination status
               Factors That May Be
              Associated With Disease
  Host Characteristics        Types of Agents and Examples      Environmental Factors

Age                      Biologic (bacteria, viruses, toxin)   Temperature
Sex                      Chemical (nerve, blister)             Humidity
Race                     Nuclear                               Altitude
Religion                 Bombs and flammables                  Wind
Customs                                                        Crowding
Occupation
Genetic profile
Marital status
Immune status
Vaccination status
               Factors That May Be
              Associated With Disease
  Host Characteristics        Types of Agents and Examples       Environmental Factors

Age                      Biologic (bacteria, viruses, toxin)   Location of Release
Sex                      Chemical (nerve, blister)             Temperature
Race                     Nuclear                               Humidity
Religion                 Bombs and flammables                  Altitude
Customs                                                        Wind
Occupation                                                     Crowding
Genetic profile
Marital status
Immune status
Vaccination status
               Factors That May Be
              Associated With Disease
  Host Characteristics        Types of Agents and Examples       Environmental Factors

Age                      Biologic (bacteria, viruses, toxin)   Location of Release
Sex                      Chemical (nerve, blister)             Temperature
Race                     Nuclear                               Humidity
Religion                 Bombs and flammables                  Altitude
Customs                                                        Wind
Occupation                                                     Crowding
Genetic profile
Marital status
Immune status
Vaccination status
               Factors That May Be
              Associated With Disease
  Host Characteristics        Types of Agents and Examples       Environmental Factors

Age                      Biologic (bacteria, viruses, toxin)   Location of Release
Sex                      Chemical (nerve, blister)             Temperature
Race                     Nuclear                               Humidity
Religion                 Bombs and flammables                  Altitude
Customs                                                        Wind
Occupation                                                     Crowding
Genetic profile
Marital status
Immune status
Vaccination status
               Factors That May Be
              Associated With Disease
  Host Characteristics        Types of Agents and Examples       Environmental Factors

Age                      Biologic (bacteria, viruses, toxin)   Location of Release
Sex                      Chemical (nerve, blister)             Temperature
Race                     Nuclear                               Humidity
Religion                 Bombs and flammables                  Altitude
Customs                                                        Wind
Occupation                                                     Crowding
Genetic profile
Marital status
Immune status
Vaccination status
               Factors That May Be
              Associated With Disease
  Host Characteristics        Types of Agents and Examples       Environmental Factors

Age                      Biologic (bacteria, viruses, toxin)   Location of Release
Sex                      Chemical (nerve, blister)             Temperature
Race                     Nuclear                               Humidity
Religion                 Bombs and flammables                  Altitude
Customs                                                        Wind
Occupation                                                     Crowding
Genetic profile
Marital status
Immune status
Vaccination status
               Factors That May Be
              Associated With Disease
  Host Characteristics        Types of Agents and Examples       Environmental Factors

Age                      Biologic (bacteria, viruses, toxin)   Location of Release
Sex                      Chemical (nerve, blister)             Temperature
Race                     Nuclear                               Humidity
Religion                 Bombs and flammables                  Altitude
Customs                                                        Wind
Occupation                                                     Crowding
Genetic profile
Marital status
Immune status
Vaccination status
               Factors That May Be
              Associated With Disease
  Host Characteristics        Types of Agents and Examples       Environmental Factors

Age                      Biologic (bacteria, viruses, toxin)   Location of Release
Sex                      Chemical (nerve, blister)             Temperature
Race                     Nuclear                               Humidity
Religion                 Bombs and flammables                  Altitude
Customs                                                        Wind
Occupation                                                     Crowding
Genetic profile
Marital status
Immune status
Vaccination status
               Factors That May Be
              Associated With Disease
  Host Characteristics        Types of Agents and Examples       Environmental Factors

Age                      Biologic (bacteria, viruses, toxin)   Location of Release
Sex                      Chemical (nerve, blister)             Temperature
Race                     Nuclear                               Humidity
Religion                 Bombs and flammables                  Altitude
Customs                                                        Wind
Occupation                                                     Crowding
Genetic profile
Marital status
Immune status
Vaccination status
               Factors That May Be
              Associated With Disease
  Host Characteristics        Types of Agents and Examples       Environmental Factors

Age                      Biologic (bacteria, viruses, toxin)   Location of Release
Sex                      Chemical (nerve, blister)             Temperature
Race                     Nuclear                               Humidity
Religion                 Bombs and flammables                  Altitude
Customs                                                        Wind
Occupation                                                     Crowding
Genetic profile
Marital status
Immune status
Vaccination status
Numerators and
 Denominators
     What Is a Numerator
• Count of cases
      What Is a Numerator
• Count of cases
• Frequently organized in a line-listing
               Line Listing
                                     a
                       Case Summaries

                     Di sease      Attendance at
                      Status       Soccer Game      Resi dence
1                                                   Di d Not
                                   Attended
                    Di seased                       Li ve wi th 1
                                   Game
                                                    m il e
2                                                   Di d Not
                                   Not Attend
                    Di seased                       Li ve wi th 1
                                   Game
                                                    m il e
3                                                   Li ved
                                   Attended
                    Di seased                       wi thi n 1
                                   Game
                                                    m il e
4                                                   Di d Not
                                   Not Attend
                    Di seased                       Li ve wi th 1
                                   Game
                                                    m il e
5                                                   Li ved
                    Not            Attended
                                                    wi thi n 1
                    Di seased      Game
                                                    m il e
6                                                   Di d Not
                    Not            Not Attend
                                                    Li ve wi th 1
                    Di seased      Game
                                                    m il e
7                                                   Di d Not
                    Not            Attended
                                                    Li ve wi th 1
                    Di seased      Game
                                                    m il e
8                                                   Li ved
                    Not            Not Attend
                                                    wi thi n 1
                    Di seased      Game
                                                    m il e
9                                                   Di d Not
                    Not            Attended
                                                    Li ve wi th 1
                    Di seased      Game
                                                    m il e
T otal    N                   9                 9               9
    a. Li mi ted to fi rst 100 cases.
     What Is a Numerator
• Count of cases
• Frequently organized in a line-listing
• Allows for regrouping and counting cases
  by their various characteristics
     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
Incidence and Prevalence

Incidence =
Incidence and Prevalence

            Number of new cases of a disease
Incidence =
                over a period of time
Incidence and Prevalence


Prevalence =
Incidence and Prevalence


               Total number of cases of a
Prevalence =            disease
    Relationship Between
  Incidence and Prevalence
                         Recovery

                          Death
Incidence

            Prevalence
               Pot
    Relationship Between
  Incidence and Prevalence
                         Recovery

                         Death
Incidence

            Prevalence
               Pot
    Relationship Between
  Incidence and Prevalence
                         Recovery

                         Death
Incidence

            Prevalence
               Pot
    Relationship Between
  Incidence and Prevalence
                         Recovery

                         Death
Incidence

            Prevalence
               Pot
    Relationship Between
  Incidence and Prevalence
                         Recovery

                         Death
Incidence

            Prevalence
               Pot
    Relationship Between
  Incidence and Prevalence
                         Recovery

                         Death
Incidence

            Prevalence
               Pot
    Relationship Between
  Incidence and Prevalence
                         Recovery

                         Death
Incidence

            Prevalence
               Pot
    Relationship Between
  Incidence and Prevalence
                         Recovery

                         Death
Incidence

            Prevalence
               Pot
    Relationship Between
  Incidence and Prevalence
                         Recovery

                         Death
Incidence

            Prevalence
               Pot
     Relationship Between
   Incidence and Prevalence
• Under the assumption of a steady-state
            Prevalence = I * D        Recovery
                                            Death

I = incidence      Incidence


                               Prevalence
D = duration                      Pot
     Relationship Between
   Incidence and Prevalence
• Under the assumption of a steady-state
            Prevalence = I * D        Recovery
                                            Death

I = incidence      Incidence


                               Prevalence
D = duration                      Pot
     Relationship Between
   Incidence and Prevalence
• Under the assumption of a steady-state
            Prevalence = I * D        Recovery
                                            Death

I = incidence      Incidence


                               Prevalence
D = duration                      Pot
       Episodes of Tularemia
     Number of Persons

20                       M
                                           L
                                          K
       J                          I
15
             H
                                               G
                              F
10
             D                             E
5
                                      C
                              B
0
                                  A
Nov. 96             Jan. 97               Jul-98   Dec. 99


                                  TIME
       Episodes of Tularemia
     Number of Persons

20                       M
                                           L
                                          K
       J                          I
15
             H
                                               G
                              F
10
             D                             E
5
                                      C
                              B
0
                                  A
Nov. 96             Jan. 97               Jul-98   Dec. 99


                                  TIME
       Episodes of Tularemia
     Number of Persons

20                       M
                                           L
                                          K
       J                          I
15
             H
                                               G
                              F
10
             D                             E
5
                                      C
                              B
0
                                  A
Nov. 96             Jan. 97               Jul-98   Dec. 99


                                  TIME
       Episodes of Tularemia
     Number of Persons

20                       M
                                           L
                                          K
       J                          I
15
             H
                                               G
                              F
10
             D                             E
5
                                      C
                              B
0
                                  A
Nov. 96             Jan. 97               Jul-98   Dec. 99


                                  TIME
       Episodes of Tularemia
     Number of Persons

20                       M
                                           L
                                          K
       J                          I
15
             H
                                               G
                              F
10
             D                             E
5
                                      C
                              B
0
                                  A
Nov. 96             Jan. 97               Jul-98   Dec. 99


                                  TIME
       Episodes of Tularemia
     Number of Persons

20                       M
                                           L
                                          K
       J                          I
15
             H
                                               G
                              F
10
             D                             E
5
                                      C
                              B
0
                                  A
Nov. 96             Jan. 97               Jul-98   Dec. 99


                                  TIME
       Episodes of Tularemia
     Number of Persons

20                       M
                                           L
                                          K
       J                          I
15
             H
                                               G
                              F
10
             D                             E
5
                                      C
                              B
0
                                  A
Nov. 96             Jan. 97               Jul-98   Dec. 99


                                  TIME
What is the prevalence of tularemia
on July 1998 in these 20 people?
      Number of Persons

 20                       M
                                            L
                                           K
        J                          I
 15
              H
                                                G
                               F
 10
              D                             E
 5
                                       C
                               B
 0
                                   A
 Nov. 96             Jan. 97               Jul-98   Dec. 99


                                   TIME
What is the prevalence of tularemia
on July 1998 in these 20 people?
      Number of Persons

 20                       M
                                            L
                                           K
        J                          I
 15
              H
                                                G
                               F
 10
              D                             E
 5
                                       C
                               B
 0
                                   A
 Nov. 96             Jan. 97               Jul-98   Dec. 99


                                   TIME
The Natural History of Disease


                                          Outcome
Healthy                                     Cure
                                           Control
    Disease Symptoms   Seek   Diagnosis   Disability
    Treatment
    Onset              Care                 Death
The Natural History of Disease


                                          Outcome
Healthy                                     Cure
                                           Control
    Disease Symptoms   Seek   Diagnosis   Disability
    Treatment
    Onset              Care                 Death
The Natural History of Disease


                                          Outcome
Healthy                                     Cure
                                           Control
    Disease Symptoms   Seek   Diagnosis   Disability
    Treatment
    Onset              Care                 Death
The Natural History of Disease


                                          Outcome
Healthy                                     Cure
                                           Control
    Disease Symptoms   Seek   Diagnosis   Disability
    Treatment
    Onset              Care                 Death
The Natural History of Disease


                                          Outcome
Healthy                                     Cure
                                           Control
    Disease Symptoms   Seek   Diagnosis   Disability
    Treatment
    Onset              Care                 Death
The Natural History of Disease


                                          Outcome
Healthy                                     Cure
                                           Control
    Disease Symptoms   Seek   Diagnosis   Disability
    Treatment
    Onset              Care                 Death

								
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