Epidemiology

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Presentation Transcript

Overview of Epidemiology: 

Overview of Epidemiology Greg Evans, PhD, MPH Institute for Biosecurity

Learning Objectives: 

Learning Objectives Define bioterrorism epidemiology Describe epidemiological approach to understanding disease etiology Recognize difference between incidence and prevalence Distinguish between the stages of the disease process

Biological and Chemical Epidemiology: 

Biological and Chemical Epidemiology The study of the distribution and determinants of diseases resulting from a biological or chemical attack

Sources of Epidemiologic Clues to a Disease Outbreak: 

Sources of Epidemiologic Clues to a Disease Outbreak Clinician’s office or medical clinic Emergency room Laboratory Veterinary Clinic Pharmacy

Epidemiologic Approach to Understanding Disease Etiology: 

Epidemiologic Approach to Understanding Disease Etiology Descriptive epidemiology - identifying associations of disease in relation to Time Place Persons

Epidemiologic Approach to Understanding Disease Etiology: 

Epidemiologic Approach to Understanding Disease Etiology Analytic epidemiology Identify associations of disease with possible etiologic factors (chemical release, biological agent) Further refine and test hypotheses regarding etiology

Problems Investigating the Causes of Disease: 

Problems Investigating the Causes of Disease Specific agent might not be known Location of agent release might not be known Signs and symptoms might not differentiate disease More than one agent might be used Time of agent release might not be known Latency period might not be known Latency is not the same for all people

Epidemiologic Triad of Disease: 

Epidemiologic Triad of Disease

Modes of Transmission: 

Modes of Transmission Direct Contact Droplets Indirect Airborne Vehicle-borne Vector-borne Mechanical Biologic Host Environment Agent

Modes of Transmission: 

Modes of Transmission Direct Contact Droplets Indirect Airborne Vehicle-borne Vector-borne Mechanical Biologic Host Environment Agent

Modes of Transmission: 

Modes of Transmission Direct Contact Droplets Indirect Airborne Vehicle-borne Vector-borne Mechanical Biologic Host Environment Agent

Modes of Transmission: 

Modes of Transmission Direct Contact Droplets Indirect Airborne Vehicle-borne Vector-borne Mechanical Biologic Host Environment Agent

Modes of Transmission: 

Modes of Transmission Direct Contact Droplets Indirect Airborne Vehicle-borne Vector-borne Mechanical Biologic Host Environment Agent

Modes of Transmission: 

Modes of Transmission Direct Contact Droplets Indirect Airborne Vehicle-borne Vector-borne Mechanical Biologic Host Environment Agent

Modes of Transmission: 

Modes of Transmission Direct Contact Droplets Indirect Airborne Vehicle-borne Vector-borne Mechanical Biologic Host Environment Agent

Factors That May Be Associated With Disease: 

Factors That May Be Associated With Disease

Factors That May Be Associated With Disease: 

Factors That May Be Associated With Disease

Factors That May Be Associated With Disease: 

Factors That May Be Associated With Disease

Factors That May Be Associated With Disease: 

Factors That May Be Associated With Disease

Factors That May Be Associated With Disease: 

Factors That May Be Associated With Disease

Factors That May Be Associated With Disease: 

Factors That May Be Associated With Disease

Factors That May Be Associated With Disease: 

Factors That May Be Associated With Disease

Factors That May Be Associated With Disease: 

Factors That May Be Associated With Disease

Factors That May Be Associated With Disease: 

Factors That May Be Associated With Disease

Factors That May Be Associated With Disease: 

Factors That May Be Associated With Disease

Factors That May Be Associated With Disease: 

Factors That May Be Associated With Disease

The Natural History of Disease: 

The Natural History of Disease

The Natural History of Disease: 

The Natural History of Disease

The Natural History of Disease: 

The Natural History of Disease

The Natural History of Disease: 

The Natural History of Disease

The Natural History of Disease: 

The Natural History of Disease

Conducting a Field Investigation: 

Conducting a Field Investigation

Conducting a Field Investigation: 

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

Conducting a Field Investigation: 

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

Steps in Conducting a Field Investigation of a Bioterrorist Event: 

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

Steps in Conducting a Field Investigation of a Bioterrorist Event: 

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

Determine If There Is an Increase in the Occurrence of Disease: 

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

Confirm the Diagnosis of Disease: 

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

Determine Definition of a Case: 

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

Analyze the Data in Terms of Time, Place, and Person to Determine Who is at Risk: 

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

Develop an Hypothesis That Explains the Specific Exposure That Caused Disease: 

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

Test Hypothesis Using Statistics: 

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 epidemiologists’ review of all the evidence before he decides on an intervention plan

Compare Hypothesis With Known Facts: 

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)

Execute Control and Prevention Measures: 

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

Plan a More Systematic Study: 

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

Prepare a Written Report: 

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