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Division of Partnerships and Strategic Alliances National Center for Health Marketing, CDC. Outbreak Investigations Ralph Cordell. Outbreaks, Epidemics & Pandemics. Same basic definition for all 3 Unusual increase in the number of illnesses in a population. Outbreak = Epidemic
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Division of Partnerships and Strategic AlliancesNational Center for Health Marketing, CDC Outbreak Investigations Ralph Cordell
Outbreaks, Epidemics & Pandemics • Same basic definition for all 3 • Unusual increase in the number of illnesses in a population. • Outbreak = Epidemic • Pandemic – multiple continents (eg. “pan-”)
Why We Investigate Outbreaks Stop spread of illness It is our job (political/legal concerns) Learn from other people’s mistakes Opportunity for research & training
Steps of an Outbreak Investigation • Prepare for field work • Establish the existence of an outbreak • Verify the diagnosis • Define and identify cases • Describe and orient the data in terms of time, place, and person • Develop hypotheses • Evaluate hypotheses • Refine hypotheses and carry out additional studies • Implement control and prevention measures • Communicate findings
Type 1 Outbreak • Single event – wedding reception, church supper, etc • Population and general source is known • Pathogen and specific cause are not known • Challenges • Identify the bug • Find the specific cause
Type 1 Outbreak • Get a list of attendees and possible exposures • Set up line list • Contact each person & interview them
Find the Bug • Wide nets • Expensive • Difficult • Catch a lot of trash and miss a lot of nuggets • Targeted • Incubation periods • Signs & symptoms • Narrow the field
Cases of Gastrointestinal Illness by Time of Onsetof Symptoms (1/2 Hour Categories) OswegoCounty, New York, April 18-19, 1940
Cases of Gastrointestinal Illnessby Time of Onset of Symptoms (Hour Categories)Oswego County, New York, April 18-19, 194
Outbreak Manifestations • Type 2 • Picked up through surveillance • Have a group of cases • Usually have a pathogen • Challenges • Find a source • What are risk factors • How do cases differ from other folks
Type 2 Outbreak • Collect cases – homogenous group • Develop hypotheses • Illness gives you some idea • Person/place characteristics • Select a group of controls • Interview both for possible exposures • Determine odds ratios for each exposure
Hep A • ICN called with 8 cases of hep A • All from NE Cook County • Hep A epi • Interviewed cases • Break in sewer line • Reports of widespread sewage contamination
Hep A • Case-control study • Field visit • Outliers