Karen L. Lancour national Committee Chairman – Life Science disclaimer




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2013 DISEASE DETECTIVES (B&C)

TRAINING HANDOUT

KAREN L. LANCOUR

National Committee Chairman – Life Science

DISCLAIMER - This presentation was prepared using draft rules.  There may be some changes in the final copy of the rules.  The rules which will be in your Coaches Manual and Student Manuals will be the official rules. BE SURE TO CHECK THE 2013 EVENT RULES for EVENT PARAMETERS and TOPICS FOR EACH COMPETITION LEVEL
TRAINING MATERIALS:

  • Training Power Point presents an overview of material in the training handout

  • Training Handout presents introductory topic content information for the event

  • Sample Tournament has sample problems with key

  • Event Supervisor Guide has event preparation tips, setup needs and scoring tips

  • Internet Resource & Training Materials are available on the Science Olympiad website at www.soinc.org under Event Information.

  • A Biology-Earth Science CD, a Disease Detectives CD as well as the Division B and Division C Test Packets are available from SO store at www.soinc.org

Event Format :

  • Format and material of the Division B and C event is similar except that the level of reasoning and math skills should be consistent with the grade level.

  • Differences between the two levels should be reflected in both the type of questions asked and the scoring rubrics. 2013 emphasis will be on environmental causes of public health problems

  • Be sure to check the event parameters in the rules for the resources allowed.

  • Format and material of the Division B and C event is similar except that the level of reasoning and math skills should be consistent with the grade level.

  • Differences between the two levels should be reflected in both the type of questions asked and the scoring rubrics.

Types of Knowledge

    • Definitions of basic epidemiologic terms

    • Categories of disease causing agents

    • Modes of disease spread

    • Triads of analysis (e.g., person/place/time & agent/host/environment)

    • The basis for taking action to control and prevent the spread of disease

Epidemiology

    • Studies health of populations instead of individuals

    • Uses the scientific method – 10 step method of investigating outbreaks

    • Studies the distribution and determinants of disease in human populations

    • Attempts to prevent and control those diseases

    • Health-related events:

    • chronic diseases

    • environmental problems

    • behavioral problems

    • injuries

    • infectious diseases

There is a three topic rotation for Disease Detectives: Environmental Quality, Population Growth, and Food Borne Illness – each on a two year rotation
2013 EmphasisSome Environmental Causes of Public Health Problems:


  • Air pollution , Smoking, Inducers of Asthma

  • Flooding health problems, Drought problems

  • Extreme heat, UV exposure

  • Lead contamination, Pesticides, Chemical Spills

  • Water pollutants, Heavy metals

  • Ventilation pollutants

  • Noise induced hearing loss

  • Waste and toxic substance

  • Food contamination


Some Population Growth Causes of Health Problems


  • Water Quality, Water Pollution, Water Demands

  • Sanitation Needs

  • Growth of Slums and Household Environment

  • Environmental Degradation

  • Air Pollution

  • Infectious Disease Outbreaks

  • Rapid Spread of Disease via Public Transportation and Air Travel

  • Food Quality and Food Contamination

  • Lack of food in poor nations vs. unhealthy fast food and drinks in technological societies

  • Availability of health care for the poor and the aged

  • People moving into uninhabited areas = new pathogens

  • as Lyme Disease and Ebola



Some Causes of Food Borne Illness


  • Bacteria

  • Viruses

  • Parasites

  • Protozoa

  • Natural toxins

  • Other pathogenic agents (as Prions)



Basic Epidemiology Terms
Outbreak – (localized epidemic) – more cases of a particular disease than expected in a given area

or among a specialized group of people over a particular period of time.



Epidemic – large numbers of people over a wide geographic area affected.

Cluster –an aggregation of cases over a particular period esp. cancer & birth defects closely

grouped in time and space regardless of whether the number is more than the

expected number. (often the expected number of cases is not known.)

pandemic -An epidemic occurring over a very wide area (several countries or continents) and usually affecting a large proportion of the population.

risk - The probability that an individual will be affected by, or die from, an illness or injury within a stated time or age span.

vector - an animate intermediary in the indirect transmission of an agent that carries the agent from a reservoir to a susceptible host. An organism that transmits the infection as a mosquito transmits the malaria protozoans.

fomite - a physical object that serves to transmit an infectious agent from person to person.

A comb infested with one or more head lice would be a fomite or the dust particles containing infectious cold virus that remain after droplets of infected saliva are coughed into the air.



zoonosis - An infectious disease that is transmissible from animals to humans.

surveillance - The systematic, ongoing collection, analysis, interpretation, and dissemination of health data. The purpose of public health surveillance is to gain knowledge of the patterns of disease, injury, and other health problems in a community so that we can work toward controlling and preventing them.

Scientific Method as related to Disease Detectives
Compare Scientific Method to 10 Steps in Outbreak Investigation


  • Obtain Background Information (Steps 1- 3)

  • Define the Problem (Step 4-5)

  • Formulate Hypothesis (Step 6)

  • Develop a Study to Test the Hypothesis (Step 7)

  • Collect Data and Observations (Step 7)

  • Evaluate Results (Step 7)

  • Determine if Hypothesis is true/modify (Step 8)

  • Formulate Conclusions (Step 9)

  • Report Results (Step 10)


10 STEPS OF AN OUTBREAK INVESTIGATION
Field investigation of disease or health condition

**- Implement control as soon as the source & mode are known!!!!

This is a conceptual order – steps may be done at the same time
Step 1: Prepare for Field Work

1. Research, supplies & equipment – research the disease or situation and gather needed

supplies & equipment to conduct the investigation

2. Administrative arrangements – make official administrative and personal travel

arrangements

3. Local contacts - follow protocol and contact all parties to determine roles & local contacts


Step 2: Establish the Existence of an Outbreak – consider severity, potential for spread, public

concern, and availability of resources

1. Expected # of cases for area – use records as health dept., hospital records, death records,

physician records, doctor survey to determine expected # for the area in a given time

2. Other factors in play – numbers may exceed normal due to factors such as better

reporting, seasonal fluctuations, population changes
Step 3: Verify the Diagnosis

1. Proper diagnosis- verify the procedures used to diagnose the problem and check methods

used for identifying infectious and toxic chemical agents

2. Not lab error – be sure that the increase number of cases are not due to experimental error

3. ­Commonality – interview several persons who became ill to gain insight concerning

possible cause, source, and spread of disease or problem


Step 4: Define and Identify Cases – case definition and line listing

1. Case definition – establish with the 4 components or standard criteria for determining

who has the disease or condition

a. Clinical information – about the disease or condition

b. Characteristics- of the affected people

c. Location or place- as specific as possible as restaurant, county, or several specific areas

d. Time sequence- specific time during which the outbreak or condition occurred

2. Identification of specific cases – kind & number – count specific cases

a. Confirmed – have diagnosis with case definition plus lab verification

b. Probable – many factors point to diagnosis but may lack lab verification

c. Possible – some factors point to diagnosis

Note: Initial reports may be only a small sampling of the total problem. Be sure to

expand search to determine the true size and extent of the problem.

3. Line Listing – chart of specific cases including information about each case

a. Identifying information- ID or case # - left column + name or initials

b. Clinical information – diagnosis, symptoms, lab results, hospital – death?

c. Descriptive: time – date & time of onset + date of report

d. Descriptive: person – age, sex, occupation, other characteristics

e. Descriptive: place – street, city or county + specific site

f. Risk factors & possible causes – specific to situation (disease) and outbreak setting



Sample Line Listing from six case report forms on a wedding reception outbreak

ID #

Initials

Date    of Onset

Diagnosis

How Confirmed

Age

Sex

County

Physician

Cleveland- 
McKay Wedding

  1

  KR

  7/23

probable trichinosis

Not done

29

  M

Columbia

Goodman

      Yes

  2

  DM

  7/27

trichinosis

Biopsy

  33

  M

Columbia

Baker

      Yes

  3

  JG

  8/14

probable trichinosis

Not done

  26

  M

Columbia

Gibbs

      Yes

  4

  RD

  7/25

trichinosis

Serologia

  45

  M

King

Webster

      Yes

  5

  NT

   8/4

trichinosis

Not done

  27

   F

Columbia

Stanley

      Yes

  6

AM

   8/11

R/Otrichinosis

Pending

  54

   F

Clayton

Mason

      Yes


Step 5: Describe and Orient the Data in Terms of Time, Place and Person – Descriptive

Epidemiology

1. Time, Place and Person – describes disease or health situation

TIME - Epidemic Curve or Epi curve (Begin early & update often) – a histogram showing

the course of the disease or outbreak to identify the source of the exposure

(x axis=units of time equal to 1/4 to 1/3 incubation time and y axis = # of cases)

Note: a single point or source will have only one peak, a plateau will show a

continuous common source, several uniform peaks will indicate a propagated outbreak spread from person to person

PLACE – geographic extent plus spot map of cases to identify groups specific to a location

or environmental factors

PERSON–identify the affected population by type of person or by exposures as age, sex,

high risk exposure as with AIDS

Sample EPI or Epidemic Curve



2. Types of Descriptive Studies – Study the distribution of a problem by cases or

outcome, frequency in population, exposure, time pattern or environmental

factor (Studies without a control group can be used for descriptive purposes!)

a. Case report/case series – case report = detail report of a single patient from

one or more doctors while case series = characteristics of several patients

b. Correlative studies – correlates general characteristics of the population with

health problem frequency with several groups during the same period of time

Time series analysis – correlate within the same population at different

point in time

Ecologic relations – correlate relative to specific ecologic factors as diet
c. Cross sectional - a survey of a population where participants are selected

irrespective of exposure or disease status

Step 6: Develop Hypotheses (Agent/host/environment triad) = chain of transmission

1. Agent /host /environment = agent capable of causing disease & its source +

host or persons susceptible to agent + environment allowing them to get together

Infectious Groups: viruses, bacteria, protistans (protozoa), fungi, animals (worms)

2. Testable – hypothesis must be in a form that is testable

3. Current knowledge & background – it should be based upon current knowledge

and be updated or modified as new information is uncovered!!!

Step 7: Evaluate Hypotheses – Analytical studies ** Must have a control group**

1. Compare with established fact – these are used when evidence is strong and clear cut

2. Must have lab verification to validate a hypothesis.

3. Two types of Studies: (Study determinants of health problems – how & why)

a. Cohort – Based upon exposure status whether or not they have outcome (illness);

used with a small well-defined population and moves forward from exposure.

Both groups have a known exposure and are checked for future outcomes or illness.

retrospective:(historic cohort) starts at exposure in past & moves forward to outcome

prospective: starts a present exposure and moves forward in time to outcome



(Calculations = attack rate and relative risk)

Sample using 2 X 2 table: 400 people attended a special awards dinner.

Some persons became ill. The suspected culprit was the potato salad.

The population at the dinner was then surveyed to determine who became ill.

 

Disease Yes

Disease No

Exposed (Ate salad)

150 (a)

30 (b)

Unexposed (no salad)

50 (c)

170 (d)



Attack rate – the rate that a group experienced an outcome or illness

= number sick ÷ total in that group

(Look for high attack rate in exposed & low rate in unexposed)

exposed = a ÷ (a+b) = 150 ÷ 180 = 80%

unexposed = c ÷ (c + d) = 50 ÷ 220 = 20%



Relative risk = [a ÷ (a+b)] / [c ÷ (c+d)] = 80% ÷ 20% = 4

  1. Relative risk estimates the extent of the association between an exposure and a disease. It estimates the likelihood of developing the disease in the exposed group as compared to the unexposed group.

  2. A relative risk = 1.0 indicates that the incidence rates of disease in the exposed group is equal to the incidence rates in unexposed group. Therefore the data does not provide evidence for an association.

  3. A relative risk >1.0 indicates a positive association or an increased risk. This risk increases in strength as the magnitude of the relative risk increases.

  4. The data indicates a negative association or decreased risk (possible protective effect) if the relative risk is between 0 and 1.0. Relative risk is not expressed in negative numbers.

b. Case-Control - Works backward from effect or illness to suspected

cause. Control group is a selected group who has similar characteristics

to the sick group but is not ill. They are then checked for similar

exposures. It is often hard to select the control group for this type of study.



Odds Ratio is calculated to evaluate the possible agents & vehicles of transmission.
Odds Ratio = Odds of exposure in cases = a/c = ad

Odds of exposure in controls b/d bc


a = # of case patients exposed b = # of control exposed

c = # of case patients unexposed d = # of control unexposed


Sample: Several patients were diagnosed with Hepatitis A. The

local Restaurant A was thought to be the source of the infection.

40 case patients and a similar disease free group or control were

contacted to determine if they ate at Restaurant A.


2 X 2 table of data:
Case patients Controls Total

Yes a = 30 b = 36 66

No c = 10 d = 70 86

Total 40 106 146

The odds ratio for Restaurant A is thus 30 × 70 / 36 × 10 = 5.8. This means that people who ate at Restaurant A were 5.8 times more likely to develop hepatitis A than were people who did not eat there.

Step 8: Refine Hypotheses and Carry Out Additional Studies

1. No confirmation of hypothesis - where analytical studies do not confirm hypothesis

May need to look for a new vehicle or mode of transmission

2. More specific – May need to be more specific in make up of case patients & controls

3. Verify with environmental/laboratory studies - verification with controlled

conditions is very important. LAB VERIFICATION NEEDED TO VALIDATE HYPOTHESIS.

Step 9: Implement Control and Prevention Measures – as soon as possible!!

1. As soon as source is known – people are sick or hurting and need help;

must know agent & source of agent + susceptibility of host+ chain of transmission

2. Aim at chain of agent-source-host – break the chain of transmission at any of its 3 points

3. May interrupt transmission or exposure – with vehicles as isolation

4. May reduce susceptibility – with immunization, legal issues and/or education

Step 10: Communicate Findings (see *** on page 6 for conclusion criteria)

1. Oral briefing – inform local health officials or other need-to-know groups

as soon as information is available

2. Written report – usually done in scientific format for future reference, legal

issues, and education



***Criteria to Draw Conclusions about Cause and Effect Relations:

1. Temporality – cause/exposure must precede effect/outcome

2. Consistency – observation of association must be repeatable in different populations at different times

3. Coherence, 1-1 relationship – exposure is always associated with outcome/ outcome is always caused by the specific exposure

4. Strength of association – relationship is clear and risk estimate is high

5. Biological plausibility – biological explanation makes sense

6. Dose/response (biologic gradient) – increasing risk is associated with

increasing exposure



Potential Types of Error in Data Collection (Div C-National only)


  • False Relationships

    • Random Error - the divergence due to chance alone, of an observation on sample from the true population value, leading to lack of precision in measurement of association

    • Bias or systematic error in an epidemiologic study that results in an incorrect estimation of the association between exposure and health-related event




  • Non-Causal Relationships – “guilt by association”

    • Confounding – occurs when the effects of two risk factors are mixed in the occurrence of the health-related event under study - when an extraneous factor is related to both disease and exposure



Random Error:

  • Is the result of fluctuations around a true value due to sampling variability

  • It can occur with data collection, coding, transfer, or analysis of data

  • Affects measurement in a inconsistent manner

  • Ways to reduce random error may include – increasing the sample size and reduce the variability in measurements


Systematic Error:

  • Occurs when there is a difference between the true value (the population) and the observed value (the sample)

  • The error is in the system used for measurement so it occurs in each occasion hence systematic error

  • Conclusions drawn on this data will be inaccurate – too great or too little

  • Validity of a study depends upon the degree of systematic error – less error equals more validity

  • Internal validity – the amount of error in measurements including those for exposure, disease, and

the association between these variables.

  • External validity –relates to the process of generalizing the finding of a study to the population from which the study is taken


Types of Bias: Describe problems in how the study is organized

  • Selection bias – occurs when study subjects are selected for the study as a result of a third unmeasured variable which is association with both the exposure and the outcome. There may be association between diseases or between characteristics and a disease related to the admission to a hospital for those with a disease, without the disease but with symptoms, and those with only the characteristics of the disease.

  • Information bias – occurs from systematic error in the assessment of a variable. Examples are information bias, response bias, interviewer bias, recall bias


Confounding: the co-occurrence or mixing of effects of extraneous factors

  • May lead to overestimating or underestimating the true association between exposure and outcome.

  • A confounding variable would be a variable (pollution) that can cause the disease under study (cancer) and is also associated with the exposure (smoking).

Examples of types of performance indicators that could be used in Division B and C events at various levels of competition.





Competition Level

Division

Division B (Middle School)

Division C (High School)

Regional/State

List and recognize examples of different modes of transmission


Calculate health-related rates (attack, incidence, prevalence, case fatality)
Calculate a simple relative risk and describe what it means
Interpret epi curves, temporal patterns and other simple graphic presentations of health data..
List, discuss and recognize examples of disease causing agents (physical and biological)
Demonstrate an understanding and ability to use terms such as endemic, epidemic and pandemic; population versus sample, association versus cause.
Describe various types of prevention and control strategies (e.g. immunization, behavior change, etc) and situations where they might be used

Recognize differences between study designs and types of error.
Calculate measures of risk (e.g. relative risk or odds ratio) when given a description of the study design
Calculate measures based on data that is not given but that can be readily extracted.
Recognize how gaps in information influence the ability to extend conclusions to the general population.

National

Understand how units affect the relative magnitude of a set of rates with different units.
Calculate appropriate measures of risk when given the study design
Complete tables when given all data needed to complete calculations.
Propose a reasonable intervention to a public health problem.
Recognize gaps in information

Recognize unmentioned factors that may influence results and types of error.
Convert between rates with different basic units (e.g. incidence per 10000 persons/year to incidence per 100 persons/week).
Propose a means to evaluate the effectiveness of an intervention or control program.




Sample Tasks: Develop sample problems for Outbreak Investigation relating to the current

year topics and then follow the 10 steps for Investigation the Outbreak to solve the problem.



Use the Sample Problem provided to help you get started.





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