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Disease Detectives

Disease Detectives

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Disease Detectives

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  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- vsexo- • 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 by positives 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

  12. Example 2: Hip fractures • case/control study, so must use OR • OR = 60/20 / 579/213 or 60*213 / 20*579 = 1.1

  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

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