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Epidemiology and Public Health

Epidemiology and Public Health. This presentation. Definition of epidemiology Beginnings of epidemiology Objectives/types of epidemiology Roles of an epidemiologist Examples Importance of communications. Definition of Epidemiology…. Student “ The worst course at medical school ”

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Epidemiology and Public Health

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  1. Epidemiology and Public Health

  2. This presentation • Definition of epidemiology • Beginnings of epidemiology • Objectives/types of epidemiology • Roles of an epidemiologist • Examples • Importance of communications

  3. Definition of Epidemiology… Student “ The worst course at medical school ” Clinicien “The science of making obscure what is already simple and clear ” Average citizen “The study of skin disease ”

  4. Definition of epidemiology The study of the distribution and determinants of the health status or events in the population and its application to control public health problems Source: Last 2001. A Dictionary of Epidemiology: 4th Edition. Oxford University Press: New York.

  5. Another definition of Epidemiology “A tool for action which promotes and protects the health of a population, based in science, causal reasoning, and common sense...”

  6. The beginning of epidemiology and public health… • Cholera epidemics in England – cause was unknown • 1831 : 22 000 deaths • 1848 : 52 000 deaths • 1853: 10,600 deaths • 1854: Epidemic of cholera in London (Soho district) • John Snow (1813-1858): physician, anesthesiologist, and “Father of Epidemiology” • Mapping of cases according to place of residence and work

  7. Cont… The distribution of cases led Snow to think that the water from pump A was causing the cholera • Most of the cases had drunk water from pump A • None of the workers at the nearby pub or workhouse had fallen sick (and had not drunk water from pump A) • Certains cases outside of the zone had drunk water from pump A

  8. The end… • Snow removed the handle of pump A and the epidemic stopped immediately • Snow did subsequent studies to confirm his hypothesis of water as a vehicle for cholera transmission

  9. And the pump without the handle is still there!!!!

  10. Objective of epidemiology in public health • Determine the burden and trend of disease • Identify the cause and mode of transmission • Identify risk factors • Guide public health measures and evaluate their impact • Guide communications

  11. The “epidemiologic triangle”Factors that can affect the occurrence of disease Agent Environment Host

  12. Types of Epidemiology • Observational • Descriptive (person, place, time, clinical features) • Analytique (makes a comparison) • Case control • Cohort • Cross-sectional • Experimental (makes a comparison, assigns controls) • Randomized, controlled • Non-randomized, controlled

  13. Observational epidemiology

  14. Principle activities of a field epidemiologist • Describean event in terms of: • Person Who ? • Place Where? • Time When? • How much Incidence/prevelence? • What Clinical features? • Analyzethe association between an event (illness, death) et its determinants (risk factors) – make comparisons • Recommendpreventive actions and control measures • Evaluate impact or changing epidemiology

  15. 30 years Recorded Influenza Pandemics 10 10 20 10 39 years? 2006 1: epidemic, 2: probable pandemic, 3: pandemic Potter, C.W: Textbook of Influenza by Nichols, Webster, Hay, Blackwell Science 1998

  16. Human Avian Influenza A/H5N1 Cases

  17. Confirmed cases of Human AI H5N1Dec 2003 to 29 May 2006 Over-all CFR: 57%

  18. Understanding the natural history of disease

  19. Expanding host range for Influenza A/H5N1 Owston Palm Civet, Domestic cat/feral cat, Stone marten, Cynomolgus macques, Ferret, New Zealand white rabbit, Leopard, Tiger, Rat, Pig Wood duck, Brazillian teal, Bahama pintail, Chestnut-breasted teal, Argentine shoveller, Domestic duck, Chiloe wigeon, Gadwall, Puna teal, Domestic goose, Lesser white-fronted goose, Bar-headed goose, Common pochard, Tufted duck, Canada goose, Red-breasted goose, Ringed teal, Manned wood-duck, Coscoroba swan, Black swan, Whooper Swan, Black-necked swan, Mute swan, White-faced whistling-duck, Smew/Common merganser, Hawaiian goose, Rosybill pochard duck, Red-crested pochard, Ruddy shelduck, Laughing gull, Brown-headed gull, Great black-headed gull, Black-headed gull, Green sandpiper, Asian open-billed stork, Grey heron, Great blue heron, Chinese pond heron, Little egret, Feral pigeon, Little cuckoo dove, Red-collared dove, Northern goshawk, Buzzard, Saker falcon, Peregrine falcon, Grey-headed fish-eagle, Serpent eagle, Crested hawk-eagle, Chukar partridge, Bobwhite quail, Japanese quail, domestic chicken, Kalij pheasant, Turkey, Pearl guineafowl, White Indian peafowl, Ring-necked pheasant, Brown (red-legged) crake, Coot, Common moorhen, Sultan (Purple swamphen), Crested mynah, House finch, Oriental magpie robin, Jungle crow, House crow, Black drongo, Hill mynah, Red-billed leiothrix, Scaly-breasted munia, Black-naped oriole, House sparrow, Eurasian tree-sparrow, Korean magpie, European starling, Zebra finch, Japanese white-eye, Great cormorant, Little cormorant, Greater flamingo, Great crested grebe, Budgerigar, Spot-bellied eagle-owl, Buffy fish-owl, Brown fish-owl, Spotted wood-owl, Emu (10 mammalian and 88 avian species)

  20. Influenza A/H5N1Likely Source of Exposure, Indonesia(data up to April 2006)

  21. ? Prerequisites of a Pandemic • A novel influenza virus must emerge to which the general population has little or no immunity and for which there is no effective vaccine • The new virus must be able to replicate in humans and cause disease • The new virus must be efficiently transmitted from one human to another causing global spread of disease

  22. Clusters in Indonesia

  23. What does the epidemiology tell us about the public health risk of an influenza pandemic? • Current extent and frequency of H5N1 outbreaks among poultry is unprecedented • Host range and geographic range is expanding • H5N1 is entrenched in poultry in Asia, where humans and poultry live in close contact • Clusters to date appear to be in blood relatives suggesting some genetic susceptibility factor • High CFR in humans who contract the illness • Efficient human-to-human transmission has not yet occurred • There is still a “window” of opportunity to prepare, but the length of the window is unknown

  24. Excellent epidemiology alone rarely leads to improvements in public health Mark White, 2002

  25. Roles of the 21st Century epidemiologist working in public health • To transform data into meaningful information to guide public health measures and maintain support for the measures • To get the information to those who can affect change • To communicate (rather than just disseminate) information • To get involved in “risk communication” • To work with various partners and across sectors to plan and implement effective strategies

  26. Working across sectorsPandemic Preparedeness Plans Animal Health Economy& Society • Animal Health Services • Biosecurity • Human Public Health • Continuity of Governance and Rule of Law • Sustaining Economic and Social Systems • Assessing vulnerability and providing humanitarian relief Human Health Humanitarian& Relief Governance& Rule of Law Coordination & Communication

  27. PAHO Documenting impact! Monitoring progress over time towards measles elimination Reported measles cases by month, Cuba, 1971-1998 Reported cases (thousands) MMR vaccine coverage (%) 6 100 5 80 Keep-up vaccination 4 60 3 Catch-up Follow-up 40 vaccinationcampaign vaccinationcampaign 2 20 1 0 0 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Month and Year Source: Ministry of Health, Cuba

  28. Documenting a changing epidemiologyCases of laboratory confirmed malaria and proportion due to P. falciparum, 1992-96

  29. Documenting a changing epidemiologyIncidence rate of pertussis notifications by age and year of onset, Australia, 1991-97 Cases /100 000 population Year Source: Australia CDI (21)23, 25 December 1997

  30. Mortality from tractor accidents by age group. Georgia, 1971-81

  31. Analytic epidemiologyCohort Studies Study Population Exposure is self selected Non-exposed Exposed Follow through time Disease No Disease Disease No Disease Source: Public Health Information Network (PHIN) Series I. North Carolina Center for Disease Preparedness and Virginia Department of Health

  32. Analytic epidemiologyCase-Control Studies Study Population Controls Cases Had Exposure No Exposure Had Exposure No Exposure Source: Public Health Information Network (PHIN) Series I. North Carolina Center for Disease Preparedness and Virginia Department of Health

  33. Table from a case control study Source: Preben Aavitsland, tables, graphs, diagrams, EPIET training

  34. Tasks of the 21st Century epidemiologist working in public health “Communications” • To maintain public confidence and trust • not just information dissemination • Instead sharing the meaning of the information • Defining/understanding the audience • Selecting the best channels • Marketing the information • a two-way process • “Communication surveillance” – listening to the concerns of the community • risk communication/social mobilization • Communicating to promote behavior change that reduces risk

  35. Epidemiology and Public HealthCommunicationsAvian influenza in Azerbaijan “During the field visits to Daikyand settlement, it emerged that risk perception at community level was limited and that local residents persistently denied avian influenza as the cause of the illnesses and deaths of affected community members…… …..Unfortunately, this difficulty in communication hampered the implementation of control measures as well as the investigation of the source of infection. Local residents did not believe that avian influenza had been diagnosed and were reluctant to provide further information that could negatively impact themselves (e.g. admitting to having de-feathered wild swans or having had contact with wild birds).” Human avian influenza in Azerbaijan, February–March 2006 WEEKLY EPIDEMIOLOGICAL RECORD, NO. 18, 5 MAY 2006

  36. Maintaining public confidence in public health measures Wakefield study published Uptake of the MMR vaccine in the UK since 1992 (source: MMR Decision Making Study, Durham University)

  37. “We had to close our school, our playroom and open special wards for measles. 11 children were in ITU and 7 were ventilated…

  38. …This was a pretty serious toll of preventable disease that children had to suffer because parents had not had their children vaccinated in sufficient numbers.”

  39. By 2000, vaccination coverage had dropped to 60%. There were a total of 1603 cases. 600 were hospitalized.

  40. Naomi Pop was too young to be vaccinated when she fell sick. She was one of 3 children who died.

  41. Understand the public

  42. Risk communications

  43. Outbreak Communications Announce early

  44. Outbreak Communications Be transparent

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