4.02 Epidemic Investigation

EPIDEMIC INVESTIGATION Lecturer: Dr. Collao Date of lecture: January 25, 2011 Transcriptionist: TransMistress Razeille

Definition of Outbreak • •

Occurrence of more cases of disease than expected in a given area among a specific group of people over a particular period of time Two or more linked cases of the same illness

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Objectives of Outbreak Investigations • • • • • • •

To determine the cause of the outbreak To control ongoing outbreaks To prevent future outbreaks To provide statutorily mandated services To strengthen surveillance at local level To advance knowledge about a disease To provide training opportunities

Specific Demands when Investigating Outbreaks • • • •

Unexpected event Need to act quickly Need for rapid control Work carried out in the field

Steps of an Outbreak Investigation •     • • 

Confirm outbreak and diagnosis Case definition and identification Descriptive data collection and analysis Develop hypothesis Analytical studies to test hypotheses Special studies Implementation of control measures Communication, including outbreak report

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Standard set of criteria for deciding if a person should be classified as suffering from the disease under investigation. Clinical criteria, restrictions of time, place, person Simple, practical, objective Sensitivity versus specificity

Probable – Patient older than 5 years with severe dehydration or dying of acute watery diarrhea in town “x” between 1 June and 20 July 2006 Confirmed – Isolation of Vibrio cholerae from stool of patient

Control the Source of Pathogen • • • •

Remove source of contamination Remove persons from exposure Inactivate / neutralize the pathogen Isolate and/or treat infected persons

Interrupt Transmission • • •

Interrupt environmental sources Control vector transmission Improve personal hygiene

Modify Host Response • •

Immunize susceptibles Use prophylactic chemotherapy

At the End • • • •

Prepare written report Communicate public health messages Influence public health policy Evaluate performance

Cessation of an outbreak occurs when there is:

Case Definition •

IV-2

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elimination of source of contamination interruption of transmission reduction/exhaustion of susceptibles modification of the effect of primary pathogen

An investigator should have knowledge on the following:

Ex. Patient older than 5 years with severe dehydration or dying of acute watery diarrhea in town “X” between 1 June and 20 July 2006

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Examples of Case Definition: • Possible – Patient with severe diarrhea

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various types of etiologic agents and the resultant disease epidemiological characteristics of outbreaks associated with different etiologic agents of resultant diseases clinical symptoms of resultant diseases environmental and food sanitation practices sources of exposure which are vulnerable to contamination with an infectious or chemical agent laboratory test available to determine causative agents read/search for additional data on studies, prevention and control

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