Epidemiology
E p id e m io lo g y   Comes from Greek words       e p i , meaning “on or upon”       d e m o s ,meaning “people”    ...
History   Hippocrates (circa 400 B.C.) attempted to explain    disease occurrence from a rational instead of a    superna...
   John Graunt, a London haberdasher, published his    landmark analysis of mortality data in 1662. He    was the first t...
Mid 1800’s   William Farr began to systematically collect and    analyze Britain’s mortality statistics.   John Snow, an...
   discipline did not flourish until the end of the    Second World War
Uses
P o p u la t io n o rc o m m u n it y h e a lt ha s s e s s me nt   What are the actual and potential health problems    ...
T h e E p id e m io lo g icApproa c h   C a s e D e f i n i t i o n – a set of standard    criteria for deciding whether ...
Statistics and Reports   When physicians diagnose a case of a reportable    disease they send a report of the case to the...
   Health departments convert the case counts into    r a t e s , which relate the number of cases to the    size of the ...
Types of Epidemiology
Descriptive Epidemiology   organize and summarize data according to time,    place, and person       Time – disease rate...
   Place - describe a health event by place to gain    insight into the geographical extent of the    problem.       Res...
Person   inherent characteristics of people   Age   Race   Sex
Acquired Characteristics   Immunity   Marital status
Activities   Occupation   Leisure activities   Use of medications/tobacco/drugs
Conditions under which people live   Socioeconomic status   Access to medical care
Analytic Epidemiology   Used to search for causes and effects, or the why    and the how.
E x p e r im e n t a l   determine the exposure status for each individual    (clinical trial) or community (community tr...
O b s e r v a t io n a l   observe the exposure and outcome status of each    study participant       c o h o r t s t u ...
Causation
   c a u s e of disease is a factor (characteristic,    behavior, event, etc.) that influences the    occurrence of disea...
E p id e m io lo g ict r ia n g le   traditional model of infectious disease causation.                        Agent     ...
Ag e nt   Infectious microorganism - must be present for    disease to occur       Virus       Bacterium              A...
Host factors   Intrinsic factors that influence an individual’s    exposure, susceptibility, or response to a causative  ...
Environmental factors       Extrinsic factors which affect the agent and the        opportunity for exposure         phy...
Epidemiology and Disease
Chain of Infection                 Mode of               Transmission                              Susceptible   Reservoir...
Chain of Infection   r e s e r v o i r of an agent is the habitat in    which an infectious agent normally lives, grows, ...
Chain of Infection   Modes of transmission       Direct – immediate transfer of the agent from a reservoir to a        s...
Chain of Infection   Portal of entry – means by which an agent    enters a susceptible host   Host – individual infected...
Epidemic D i s e a s eO c c urre nc e   Level of Disease - amount of a particular    disease that is usually present in a...
   Sporadic - irregular pattern of occurrence, with    occasional cases occurring at irregular intervals
   Endemic - persistent level of occurrence with a    low to moderate disease level
   Epidemic or Outbreak- occurrence of a disease    within an area is clearly in excess of the expected    level for a gi...
   Pandemic - an epidemic spreads over several    countries or continents, affecting a large number    of people
Upcoming SlideShare
Loading in...5
×

Epidemiology

705

Published on

Published in: Health & Medicine
0 Comments
2 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total Views
705
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
0
Comments
0
Likes
2
Embeds 0
No embeds

No notes for slide

Epidemiology

  1. 1. Epidemiology
  2. 2. E p id e m io lo g y Comes from Greek words  e p i , meaning “on or upon”  d e m o s ,meaning “people”  l o g o s , meaning “the study of” Study of distribution and determinants of health-related conditions or events in populations
  3. 3. History Hippocrates (circa 400 B.C.) attempted to explain disease occurrence from a rational instead of a supernatural viewpoint
  4. 4.  John Graunt, a London haberdasher, published his landmark analysis of mortality data in 1662. He was the first to quantify patterns of birth, death, and disease occurrence, noting male-female disparities, high infant mortality, and seasonal variations
  5. 5. Mid 1800’s William Farr began to systematically collect and analyze Britain’s mortality statistics. John Snow, an anesthesiologist, conducted a series of investigations in London that later earned him the title “the father of epidemiology.”
  6. 6.  discipline did not flourish until the end of the Second World War
  7. 7. Uses
  8. 8. P o p u la t io n o rc o m m u n it y h e a lt ha s s e s s me nt What are the actual and potential health problems in the community? Where are they? Who is at risk? Which problems are declining over time? Which ones are increasing or have the potential to increase? How do these patterns relate to the level and distribution of services available?
  9. 9. T h e E p id e m io lo g icApproa c h C a s e D e f i n i t i o n – a set of standard criteria for deciding whether a person has a particular disease or other health-related condition.
  10. 10. Statistics and Reports When physicians diagnose a case of a reportable disease they send a report of the case to their local health department.  Time - when the case occurred  place - where the patient lived  person - the age, race, and sex of the patient
  11. 11.  Health departments convert the case counts into r a t e s , which relate the number of cases to the size of the population where they occurred
  12. 12. Types of Epidemiology
  13. 13. Descriptive Epidemiology organize and summarize data according to time, place, and person  Time – disease rates change over time – the seasonal increase in influenza with the onset of cold weather  time data is usually shown on a graph
  14. 14.  Place - describe a health event by place to gain insight into the geographical extent of the problem.  Residence  Birthplace  place of employment  school district  hospital unit, etc
  15. 15. Person inherent characteristics of people Age Race Sex
  16. 16. Acquired Characteristics Immunity Marital status
  17. 17. Activities Occupation Leisure activities Use of medications/tobacco/drugs
  18. 18. Conditions under which people live Socioeconomic status Access to medical care
  19. 19. Analytic Epidemiology Used to search for causes and effects, or the why and the how.
  20. 20. E x p e r im e n t a l determine the exposure status for each individual (clinical trial) or community (community trial); we then follow the individuals or communities to detect the effects of the exposure
  21. 21. O b s e r v a t io n a l observe the exposure and outcome status of each study participant  c o h o r t s t u d y - categorize subjects on the basis of their exposure and then observe them to see if they develop the health conditions being studied  c a s e -c o n t r o l study - enroll a group of people with disease (“cases”) and a group without disease (“controls”) and compare their patterns of previous exposures
  22. 22. Causation
  23. 23.  c a u s e of disease is a factor (characteristic, behavior, event, etc.) that influences the occurrence of disease  An increase in the factors leads to an increase in disease.  Reduction of the factors leads to a reduction in disease
  24. 24. E p id e m io lo g ict r ia n g le traditional model of infectious disease causation. Agent Host Environment
  25. 25. Ag e nt Infectious microorganism - must be present for disease to occur  Virus  Bacterium Agent  Parasite  other microbe Host Environment
  26. 26. Host factors Intrinsic factors that influence an individual’s exposure, susceptibility, or response to a causative agent.  Age Agent  Race  Sex  socioeconomic status  behaviors Host Environment
  27. 27. Environmental factors Extrinsic factors which affect the agent and the opportunity for exposure  physical factors  biologic factors Agent  socioeconomic factors Host Environment
  28. 28. Epidemiology and Disease
  29. 29. Chain of Infection Mode of Transmission Susceptible Reservoir Host Mode of Transmission
  30. 30. Chain of Infection r e s e r v o i r of an agent is the habitat in which an infectious agent normally lives, grows, and multiplies. P o r t a l o f e x i t is the path by which an agent leaves the source host
  31. 31. Chain of Infection Modes of transmission  Direct – immediate transfer of the agent from a reservoir to a susceptible host by direct contact or droplet spread  Direct contact  Droplet spread  Indirect – an agent is carried from a reservoir to a susceptible host by suspended air particles or by animate (v e c t o r ) or inanimate (v e h i c l e ) intermediaries  Airborne  Vehicleborne  Vectorborne  Mechanical  Biologic
  32. 32. Chain of Infection Portal of entry – means by which an agent enters a susceptible host Host – individual infected with the agent
  33. 33. Epidemic D i s e a s eO c c urre nc e Level of Disease - amount of a particular disease that is usually present in a community Increasing amount of disease Pandemic Epidemic Endemic Sporatic
  34. 34.  Sporadic - irregular pattern of occurrence, with occasional cases occurring at irregular intervals
  35. 35.  Endemic - persistent level of occurrence with a low to moderate disease level
  36. 36.  Epidemic or Outbreak- occurrence of a disease within an area is clearly in excess of the expected level for a given time period
  37. 37.  Pandemic - an epidemic spreads over several countries or continents, affecting a large number of people

×