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Disease Detectives B/C. What is Disease Detectives? Epidemiology: Study of health/sickness of populations Includes Public Health Surveillance –Data collection.

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Presentation on theme: "Disease Detectives B/C. What is Disease Detectives? Epidemiology: Study of health/sickness of populations Includes Public Health Surveillance –Data collection."— Presentation transcript:

1 Disease Detectives B/C

2 What is Disease Detectives? Epidemiology: Study of health/sickness of populations Includes Public Health Surveillance –Data collection for prevention and control of illness Uses scientific study methods –Heavy emphasis on data analysis

3 The event B/C events similar in content C has more math, vocab, evaluation of research design Nonprogrammable calculators (absolutely essential) One sheet of notes This year’s focus: foodborne illness –Includes prevention and remediation

4 Event format 2-3 data sets on public health problems Mostly short answer/fill in questions Multi-point math problems –Show work for partial credit! Matching/multiple choice for vocab Essays, long reading passages? –“ten steps to investigating an outbreak”

5 Major foodborne agents Viruses: Norwalk/norovirus; rotavirus, hep A (a) Bacteria: Campylobacter, Salmonella, E. coli O157:H7, Clostridium perfringens, Listeria, Staphylococcus, Shigella, Vibrio, Yersinia (a); C. botulinum (c) Bacterial toxins: endo- vs exo- Contaminants: melamine, mercury etc. (a, c) Toxins: seafood, mushrooms, berries (all) Parasites and prions (a, c) Symptoms: a) gastroenteritis, b) allergic, c) neurological – see chart

6 Biology of disease Virus, bacteria, parasite – life cycles, modes of transmission Immunity: active, passive, herd Epidemic, pandemic, endemic Case definition: person, place, time Epidemiological triad: agent, host, environment John Snow’s cholera study

7 Statistics Prevalence: #of existing cases at a given time (or period) Incidence: # of new cases in a period of time Both usually expressed as rates (e.g., per 1,000 pop.) –For incidence, person/time may be used (e.g., person/year) Attack rate: cases/exposed pop. Case fatality rate: CSD/cases

8 Statistics: Relative Risk Technically, Relative Risk includes Risk Ratio, Rate Ratio and Odds Ratio Usually, Relative Risk = Risk Ratio Risk = # of cases/population Risk Ratio = risk in pop. of interest / control group risk may be study pop./general population OR exposed/unexposed

9 Odds Ratio Odds of outcome in pop. 1 odds of outcome in pop.2 = postives in pop. 1 negatives in pop. 1 divided bypositives in pop. 2 negatives in pop. 2 Or, by invert and multiply pos. in pop.1 X neg. in pop. 2 neg. in pop. 1 X pos. in pop.2

10 Research methods Case/control study: compare cases to some group of unaffected persons –Cannot use RR b/c no true baseline Cohort study: tracks population over time, compares to some baseline –Can use RR –May be prospective or retrospective Experimental methods –Basically limited to randomized clinical trials of treatments, supplements etc.

11 Example: Nurses’ health study Cohort study (prospective), so RR is applicable RR = 411/39242 / 596/74068 RR = 1.30 Breast Cancer + No Breast Cancer Totals Ever smoked4113883139242 Never Smoked5967347274068 Totals1007112303113,310

12 Example 2: Hip fractures case/control study, so must use OR OR = 60/20 / 579/213 or 60*213 / 20*579 = 1.1 # of months on hormone replacement therapy Hip fracture patients (Cases) Sample of other patients (controls)Totals > 660579639 < 620213233 Totals80792872

13 Epi curves: point source Single peak, <1 incubation period Single environmental source; no PTP Example: transient environmental agents, most food contamination

14 Continuous common source One peak or declining peaks, >1 IP Ongoing environmental exposure; no PTP Example: persistent environmental agents, waterborne pathogens (cholera)

15 Progressive source (aka Propagated) Multiple, often successively higher peaks >1 IP Person-to person transmission Example: communicable diseases (MRSA, flu)

16 Line Listing Signs/SymptomsLabDemographics Case #Report Date Onset Date Physician Diagnosis NVJHAIgMSexAge 110/12/0210/5/02Hepatitis A1111M37 210/12/0210/4/02Hepatitis A1011M62 310/13/0210/4/02Hepatitis A1011M38 410/13/0210/9/02NA000 F44 510/15/02 10/13/02Hepatitis A1101M17 610/16/0210/6/02Hepatitis A0011F43

17 SIR Graph susceptible, infected, recovered (removed)

18 Contagion Now a major motion picture Made with the cooperation of the CDC Go see it! Make your students see it! It is really good!

19 Links National site resources: http://soinc.orghttp://soinc.org Soinc store: http://store.soinc.org/http://store.soinc.org/ Free online introductory textbook from the CDC: http://www.ihs.gov/MedicalPrograms/PortlandInjury/PDFs/PrinciplesOfEpi demiologyInPublicHealthPractice.pdf http://www.ihs.gov/MedicalPrograms/PortlandInjury/PDFs/PrinciplesOfEpi demiologyInPublicHealthPractice.pdf CDC’s DD site: http://www.cdc.gov/excite/disease_detectives/index.htmhttp://www.cdc.gov/excite/disease_detectives/index.htm Weekly reports from CDC: http://www.cdc.gov/mmwr/http://www.cdc.gov/mmwr/ Awesome chart of foodborne agents: http://www.doh.wa.gov/notify/other/foodchart.pdf http://www.doh.wa.gov/notify/other/foodchart.pdf Glossaries: http://www.cdc.gov/reproductivehealth/EpiGlossary/glossary.htm#C http://www.ispub.com/ostia/index.php?xmlFilePath=journals/ijpn/vol3n1/gl ossary.xml http://www.cdc.gov/reproductivehealth/EpiGlossary/glossary.htm#C http://www.ispub.com/ostia/index.php?xmlFilePath=journals/ijpn/vol3n1/gl ossary.xml Nice explanation of odds ratio & relative risk: http://www.childrens- mercy.org/stats/journal/oddsratio.asphttp://www.childrens- mercy.org/stats/journal/oddsratio.asp Epi curves: http://nccphp.sph.unc.edu/focus/vol1/issue5/1- 5EpiCurves_issue.pdfhttp://nccphp.sph.unc.edu/focus/vol1/issue5/1- 5EpiCurves_issue.pdf


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