Outbreaks

The Georgia Department of Public Health, Division of Public Health (DPH) in accordance with the Official Code of Georgia, Title 31-12-1, is "...empowered to conduct studies, research, and training appropriate to the prevention of disease..." All physicians, laboratorians, and other healthcare providers are required by law to immediately report any cluster of illnesses to the Division of Public Health. Clusters or outbreaks may be reported to the appropriate County Health Department or District Health Office, or to the DPH 24/7 reporting hotline, 1-866-PUB-HLTH (1-866-782-4584), or they may also be directly reported to the Acute Disease Epidemiology Section at the Division of Public Health at 404-657-2588.

The Acute Disease Epidemiology Section (ADES) is responsible for supporting the District Epidemiologists in outbreak investigations, coordinating clinical and environmental specimen testing at the Georgia Public Health Laboratory (GPHL), and managing statewide outbreak related data. ADES epidemiologists also work closely with the Centers for Disease Control and Prevention (CDC), the Georgia Department of Agriculture, and the Food and Drug Administration for technical support and collaboration on multistate investigations.

What is an outbreak?

An outbreak is defined as more cases of disease in time or place than expected. If the condition is rare (i.e. foodborne botulism) or has serious public health implications (i.e. bioterrorism agent), an outbreak may involve only one case. When two or more cases have the same laboratory diagnosis of the etiologic agent, the outbreak is considered laboratory confirmed. A cluster is a group of cases linked together in place and time (and may represent an outbreak). Not all clusters are outbreaks but all clusters are investigated thoroughly and rapidly to rule out an outbreak or to implement control measures.

Georgia epidemiologists are responsible for outbreak investigations involving Georgia residents regardless of the exposure location. Outbreaks involving residents from multiple states are usually coordinated by CDC. Investigations into the source of an outbreak or cluster can vary with the etiology involved (viral, bacterial, parasitic, or chemical), the mode of transmission (foodborne, waterborne, environmental, person-to-person), or the setting (restaurant, nursing home, school, community.

Epidemiologists in Georgia use the following ten steps to investigate every outbreak. This standardized approach ensures timely response and thorough investigation into the cause of any outbreak so that it can be stopped and/or further disease can be prevented.

Outbreak Investigation: 10 Steps

1. Prepare to investigate
   1. Identify outbreak investigation team
   2. Review scientific literature
   3. Determine if immediate control measures are needed
2. Verify the diagnosis and confirm outbreak
   1. Get laboratory confirmation
   2. Collect stool specimens from ill persons
   3. Perform bacteriologic, virologic or parasitic testing at the Georgia Public Health Laboratory (GPHL)
   4. Link patients and environmental specimens by DNA fingerprinting/Pulse Field Gel Electrophoresis (PFGE)
3. Case definition
   1. Establish a set of standard criteria for deciding who are the ill persons related to the outbreak ("case-patients")
   2. Narrow or broad (confirm, probable, suspect)
   3. DYNAMIC: may change during investigation
4. Case finding
   1. Conduct systematic search based on case definition
   2. Create line list of possible cases (people exposed)
5. Perform descriptive epidemiology
   1. Tabulate and orient data: PERSON, PLACE, TIME
   2. Frequencies
   3. Mapping
   4. Epidemic Curve
6. Hypothesis generation - the how and the why
   1. Compare with known sources or similar outbreaks
   2. Design questionnaire
7. Evaluate hypothesis through statistics
   1. Perform epidemiologic study: cohort, case-control
   2. Compare risk factors among ill (cases) vs not ill (controls)
8. Additional environmental studies
   1. Collect food, water, and/ or environmental samples
   2. Determine what happened with the implicated source or food
9. Implement control/prevention measure
   1. Coordinate with all stakeholders including regulatory partners
   2. Develop strategies to prevent further or future illness
10. Communicate findings
    1. Disseminate outbreak investigation report - internal and external audience
    2. Educate community, ill persons, restaurant staff, and Public Health Staff