Conducting a Field Investigation

1. Conducting a Field Investigation Bioterrorism Epidemiology Module 9 Missouri Department of Health And Senior Services

2. Conducting a Field Investigation • When possible, collect information that describes: • When people became ill • Where they acquired the disease • Characteristics of the people

3. Conducting a Field Investigation • When descriptive information does not readily indicate risk factors, analytical methods will be required: • Determining rates and comparing them • Comparing ill and well or • Comparing exposed and unexposed • Most analysis should be done in the field

4. Steps in Conducting a Field Investigation of a Bioterrorist Event • Determine if there is an increase in the occurrence of disease • Confirm the diagnosis of disease • Determine definition of a case • Analyze the data in terms of time, place, and person • Determine who is at risk for becoming ill

5. Steps in Conducting a Field Investigation of a Bioterrorist Event • Develop an hypothesis that explains the specific exposure that caused disease • Test hypothesis using statistics • Compare hypothesis with known facts • Execute control and prevention measures • Plan a more systematic study • Prepare a written report Adapted from MB Gregg, Field Epidemiology

6. Determine if There is an Increase in the Occurrence of Disease • Initial indication of an increase might be syndromic only • Might need to check hospital and clinic records for increase in symptoms • Might need to telephone a sample of physicians • Might require a rapid community survey • Might be difficult to distinguish between a disease outbreak related to bioterrorism and one from other causes

7. Confirm the Diagnosis of Disease • Frequently requires laboratory techniques • Can not always wait for confirmation before starting treatment and prophylaxis • Might only require laboratory confirmation of first few cases before relying solely on signs and symptoms

8. Determine Definition of a Case • Use sign and symptoms or simple rapid laboratory techniques • At this point, it is more important to include all possible cases (high sensitivity) • Use simple case definition to initiate immediate treatment

9. Analyze the Data in Terms of Time, Place, and Person to Determine Who is at Risk • When did patients first start becoming ill? • Where were they when they became ill? • What were their activities prior to becoming ill and where were they performing these activities? • What are the characteristics of the ill person?

10. Develop an Hypothesis That Explains the Specific Exposure That Caused Disease • The origin of the specific exposure might not be obvious • Can be the most challenging aspect of the investigation

11. Test Hypothesis Using Statistics • Statistics provide a set of tools that help an epidemiologist reduce the role of chance in hypothesis testing • Statistics can not substitute for an epidemiologist’s review of all the evidence before deciding on an intervention plan

12. Compare Hypothesis With Known Facts • Is the hypothesis in agreement with laboratory, clinical, and other epidemiological evidence? • Might need to consult other scientific disciplines (e.g. medicine, biology, environmental science, laboratory science)

13. Execute Control and Prevention Measures • Get to this step as quickly as possible, particularly in case of a highly lethal agent • Sometimes must make decisions that rely on incomplete information • Decisions must be continually reviewed as new information is obtained

14. Plan a More Systematic Study • As control measures are initiated, additional questions will arise that will require additional studies • These studies should use the most applicable epidemiological study methods available

15. Prepare a Written Report • A document for action • A record of performance • A document for potential medical/legal issues • A systematic review of the investigational methods that might suggest additional analysis • A document that will help others investigate and control future bioterrorist attacks