Disease Detectives

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Disease Detectives

• B/C

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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

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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 years focus foodborne illness
• Includes prevention and remediation

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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

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Major foodborne agents

• Viruses Norwalk/norovirus rotavirus, hep A (a)
• Bacteria Campylobacter, Salmonella, E. coli
  O157H7, 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

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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 Snows cholera study

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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

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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

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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

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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.

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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 smoked 411 38831 39242
Never Smoked 596 73472 74068
Totals 1007 112303 113,310
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Example 2 Hip fractures
of months on hormone replacement therapy Hip fracture patients (Cases) Sample of other patients (controls) Totals
gt 6 60 579 639
lt 6 20 213 233
Totals 80 792 872

• case/control study, so must use OR
• OR 60/20 / 579/213 or
• 60213 / 20579 1.1

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Epi curves point source

• Single peak, lt1 incubation period
• Single environmental source no PTP
• Example transient environmental agents, most
  food contamination

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Continuous common source

• One peak or declining peaks, gt1 IP
• Ongoing environmental exposure no PTP
• Example persistent environmental agents,
  waterborne pathogens (cholera)

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Progressive source(aka Propagated)

• Multiple, often successively higher peaks gt1 IP
• Person-to person transmission
• Example communicable diseases (MRSA, flu)

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Line Listing
        Signs/Symptoms Signs/Symptoms Signs/Symptoms Lab Demographics Demographics
Case Report Date Onset Date Physician Diagnosis N V J HAIgM Sex Age
1 10/12/02 10/5/02 Hepatitis A 1 1 1 1 M 37
2 10/12/02 10/4/02 Hepatitis A 1 0 1 1 M 62
3 10/13/02 10/4/02 Hepatitis A 1 0 1 1 M 38
4 10/13/02 10/9/02 NA 0 0 0 NA F 44
5 10/15/02 10/13/02 Hepatitis A 1 1 0 1 M 17
6 10/16/02 10/6/02 Hepatitis A 0 0 1 1 F 43
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SIR Graph

• susceptible, infected, recovered (removed)

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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!

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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/PrinciplesOfEpidemiologyInPublicHealthPractic
  e.pdf
• CDCs DD site http//www.cdc.gov/excite/disease_d
  etectives/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.htmC http//www.ispub.com/o
  stia/index.php?xmlFilePathjournals/ijpn/vol3n1/gl
  ossary.xml
• Nice explanation of odds ratio relative risk
  http//www.childrens-mercy.org/stats/journal/oddsr
  atio.asp
• Epi curves http//nccphp.sph.unc.edu/focus/vol1/i
  ssue5/1-5EpiCurves_issue.pdf