introduction to epidemiology (2) to epidemiology (2).pdfintroduction to epidemiology joshua vest...
TRANSCRIPT
![Page 1: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/1.jpg)
Introduction to Epidemiology
Joshua VestEpidemiologist
Austin/Travis County Health & Human Services Department
University of Texas � April 21, 2003
![Page 2: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/2.jpg)
Outline
! Define! History! Basis of epidemiology! Objectives of epidemiology! Causal inference
![Page 3: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/3.jpg)
Epidemiology
! The study of the distribution and determinants of health-related states or events in specified populations and the application of this study to the control of health problems
![Page 4: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/4.jpg)
Epidemiology
! The study of how disease is distributed in a population and of the factors that influence or determine that distribution.
![Page 5: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/5.jpg)
History of epidemiology! John Snow, 1854
! Cholera outbreak in London! Snow had previously hypothesized cholera
was transmitted via water.! Two water companies in London! One pulled water down stream from
sewage, one from up stream! Deaths occurred around water pumps from
the downstream company
![Page 6: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/6.jpg)
![Page 7: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/7.jpg)
Basis of epidemiology
Disease, illness and ill-health are not randomly distributed in a population.
![Page 8: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/8.jpg)
Determinants of diseaseHost
Agent Environment
![Page 9: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/9.jpg)
Agent
! A necessary ingredient in the production of disease
! May be infectious (virus, bacteria) or noninfectious (chemical, radiation)
! May be a single agent or a complex of agents
![Page 10: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/10.jpg)
Host
! The biological and behavioral qualities of an individual
! Factors can influence the exposure to disease causing agents and the occurrence of disease after exposure
![Page 11: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/11.jpg)
Host
! Age! Sex! Race/ethnicity! Occupation! Immune status! Alcohol / drug use! Sexual activity
![Page 12: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/12.jpg)
Environment
! External factors that affect the likelihood of disease occurrence
! Examples: weather, population density, geography
![Page 13: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/13.jpg)
Objectives of epidemiology1. Identify the causes of disease and the
factors that increase a person�s risk of disease
2. Describe the extent of disease found in a community
3. Describe the natural history and characteristics of a disease
4. Evaluate preventive/therapeutic measures5. Guide policy decisions
![Page 14: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/14.jpg)
1. Identify causes of disease
! Classic application of infectious disease epidemiology
! Outbreak or cluster investigations! Medical detective
![Page 15: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/15.jpg)
Examples of outbreak investigations
! Pneumonia associated with convention attendants discovered Legionnaires Disease
! SARS cases in Toronto traced back to exposures in Hong Kong
! Deaths due to E.coli from eating at fast food restaurants
![Page 16: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/16.jpg)
Local outbreak examples
! A case of Hemolytic Uremic Syndrome caused by E Coli from a church retreat
! Outbreak of shigella after a 21st
birthday party caused by one of the guests
![Page 17: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/17.jpg)
2. Describe the extent of disease
! Descriptive epidemiology! Person � populations/communities
affected! Place � geographical locations! Time � seasonal patterns, trends over
time
![Page 18: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/18.jpg)
020406080
100120140160180200
1990
1991
1 992
1 993
199 4
1 995
199 6
1 997
199 8
199 9
2000
200 1
YEAR OF REPORT
CAS
ES P
ER 1
00,0
00
White
Black
Hispanic
AIDS case rates by race/ethnicity*
*Austin EMA
![Page 19: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/19.jpg)
2. Describe the extent of disease
! Epidemic � any disease that occurs at a greater than expected frequency
! Endemic � any disease that does not fluctuate over time in a defined place
![Page 20: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/20.jpg)
3. Natural history & characteristics
! the natural development of a disease over time
! modes of transmission! distribution! prognosis
![Page 21: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/21.jpg)
0
20000
40000
60000
80000
100000
120000
1900
1902
1904
1906
1908
1910
1912
1914
1916
1918
1920
1922
1924
1926
1928
1930
1932
1934
1936
1938
1940
1942
1944
1946
1948
1950
num
ber
Cases Deaths
Smallpox in the US, 1900-1950
From “Smallpox & Its Eradication”
![Page 22: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/22.jpg)
Smallpox: eradication
! 1949 � last US case! 1967 � eradicated from Western
Hemisphere, except for Brazil! 1967 � global eradication program
began! 1977 � last indigenous case in Somalia! 1980 � WHO certifies global eradication
![Page 23: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/23.jpg)
Smallpox: reservoir
! Humans are the only natural host! No chronic carrier status
![Page 24: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/24.jpg)
Smallpox: temporal pattern
! Seasonality similar to measles and chickenpox
! Incidence was highest in winter and spring
! Virus is more viable at low temperatures and humidity
![Page 25: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/25.jpg)
Smallpox : transmission
! Most transmission occurs from direct face-to-face contact, usually ≤ 6 feet with infected persons
! Direct contact with infected materials or scabs
! Highly infectious
![Page 26: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/26.jpg)
Smallpox: outcomes
! High fatality rate: 20 � 40% of ill individuals die
! Pockmarks: scarring left on body and face
! Blindness: result of co-infection! Encephalitis
![Page 27: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/27.jpg)
Case fatality rates by age
8%11%Indonesia (West Java)
8%10%Tango13%14%West Africa
13%18%Indonesia (Jakarta)15%18%India (Punjab)16%19%Afghanistan17%23%Burma26%43%India (Tamil Nadu)
18.5%26.8%36%47%Bangladesh
All ages0-4Country (area)
From “Smallpox and Its Eradication”
![Page 28: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/28.jpg)
4. Evaluation
! Determine the effectiveness of health programs and services in improving the health of the community
![Page 29: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/29.jpg)
Evaluation of Health Study
MeasureBMI
MeasureBMI
B
MeasureBMI
AerobicsMeasureBMI
A
Post-testInterventionPre-testGroup
![Page 30: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/30.jpg)
Inactivated vaccine
Live oral vaccine
Last indigenous case
*2001 provisional data0
5000
10000
15000
20000
25000
1950 1956 1962 1968 1974 1980 1986 1992 1998
Cas
es
Inactivated vaccine
Live oral vaccine
Last indigenous case
*2001 provisional data CDC
Poliomyelitis�US, 1950-2001*
![Page 31: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/31.jpg)
5. Policy
! Warnings on cigarettes! Targeted community interventions! Smallpox preparedness program! Polio eradication program
![Page 32: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/32.jpg)
Applications of epidemiology! Clinical! Genetic! Social! Infectious Disease! Chronic Disease! Pharmacoepidemiology! HIV/AIDS! Maternal & child
![Page 33: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/33.jpg)
Causal Inference
! Does an exposure or factor cause disease?
! More than is a factor statistically associated with disease.
![Page 34: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/34.jpg)
Exposure
Disease or Outcome
Statistical association
Exposure
Disease or Outcome
Statistical association
Association Causal Association
![Page 35: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/35.jpg)
Criteria for causal association
! Temporal relationship! Strength of relationship! Dose-response relationship! Biologic plausibility! Consistency of results
![Page 36: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/36.jpg)
Causal inference
! Temporal association! Does the exposure precede the disease?
![Page 37: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/37.jpg)
Causal inference
! Strength of relationship! The stronger the association, the more
likely it is that the exposure-disease relationship is causal
! Strong associations are not as likely as weak association to be due to different types of study bias
![Page 38: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/38.jpg)
Causal inference
! Dose-response relationship! Is the association stronger with increased
intensity or duration of exposure?
![Page 39: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/39.jpg)
Dose-response relationship
3.4
51.4 59.3
143.9
217.3
0
50
100
150
200
250
Neversmoked
<1/2 pack/ day
1/2-1 pack/ day
1-2 packs /day
2+ packs /day
mor
atal
ity
rate
per
100
,000
From: Hammond & Horn, JAMA 166:194-1308; 1958
![Page 40: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/40.jpg)
Causal inference
! Biologic plausibility! Results consistent with current knowledge
of biology?! Are there any known or suspected
biological mechanisms that help explain the exposure-disease association?
![Page 41: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/41.jpg)
Causal inference
! Consistency of results! Do other studies with different populations
and methods report the same results?
![Page 42: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/42.jpg)
More information
For more information on epidemiology
Epidemiology Supercoursehttp://www.pitt.edu/~super1/
![Page 43: Introduction to Epidemiology (2) to Epidemiology (2).pdfIntroduction to Epidemiology Joshua Vest Epidemiologist Austin/Travis County ... factors that increase a person™s risk of](https://reader030.vdocument.in/reader030/viewer/2022033123/5e5fffce15bcae66022c0870/html5/thumbnails/43.jpg)
Contact informationJoshua Vest
EpidemiologistAustin/Travis County
Health & Human Services Department