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Epidemiologic Surveillance and Outbreak Investigation

Epidemiologic Surveillance and Outbreak Investigation. Presented by CPT Kathy Hughes DVM, TXSG Houston Med Response Group Texas Medical Rangers 23 Mar 05. Epidemiology. The study of diseases and health in populations

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Epidemiologic Surveillance and Outbreak Investigation

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  1. Epidemiologic Surveillance and Outbreak Investigation Presented by CPT Kathy Hughes DVM, TXSG Houston Med Response Group Texas Medical Rangers 23 Mar 05

  2. Epidemiology • The study of diseases and health in populations • The study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems • Last JM, ed. Dictionary of Epidemiology, Second edition. New York: Oxford U. Press, 1988: 42. • Basic science of public health

  3. Risk factor • Exposure associated with occurrence of disease • Not necessarily causative

  4. Outbreak • Occurrence of increased number of cases of a disease above the expected frequency

  5. Surveillance • Monitoring diseases in population • Passive: reports submitted by practitioners, laboratories, hospitals • Reportable diseases • Active: public health officials contact health care facilities for information

  6. 1. Establish existence of outbreak 2. Verify diagnosis 3. Develop case definition 4. Perform descriptive epidemiology 5. Analyze data 6. Develop hypothesis 7. Test hypothesis 8. Refine hypothesis 9. Implement control measures 10. Write report and disseminate findings Outbreak investigation

  7. Anthrax outbreak • Fall 2001 • First case of bioterrorism in U.S. • Investigation led by Centers for Disease Control (CDC)

  8. Anthrax • Agent: Bacillus anthracis • Inhalational • Cutaneous • Gastrointestinal

  9. 1. Establish existence of outbreak • 22 cases of anthrax diagnosed October-November 2001 • 11 cases of inhalational anthrax • Last reported case of inhalational anthrax in U.S. was in 1976

  10. 2. Verify diagnosis • Clinical findings • Skin lesions, fever, cough, chest pain • Laboratory findings • Isolation of B. anthracis from patient • PCR of B. anthracis DNA • Immunohistochemical staining • Serology with ELISA

  11. 3. Establish case definition • Confirmed • Clinical signs plus isolation or 2 supportive lab tests • Suspected • Clinical signs plus 1 supportive lab test or link to environmental exposure

  12. Search for more cases • Search for more cases • Hospital, clinic, medical examiners • Staff at affected workplaces • Reports from law enforcement and public • Collect data • Develop and administer questionnaire • Cases and those potentially exposed • Test clinical and environmental specimens • 4 powder-containing envelopes recovered

  13. 4. Perform descriptive epidemiology • Who, what, where, when • Plot epidemic curve • Dates of onset of illness • Plot spot map • Locations of cases

  14. 5. Analyze data • Calculate frequency rates from descriptive epidemiology • Age • Sex • Occupation • Case-fatality ratio

  15. 6. Develop hypothesis • Why and how • 2 separate mailings • Exposures along path of mail and at delivery locations

  16. 7. Test hypothesis • Evaluate relationship between exposure and disease • Compared cases between mailings • Type of occupation • Form of anthrax • Cases: persons with the disease • Controls: persons without the disease

  17. 8. Refine hypothesis • If original hypothesis failed • May require further studies

  18. 9. Implement control measures • Treatment of cases • Postexposure prophylaxis • Inhalational case at workplace • Environmental specimens at workplace • 32,000 people received prophylaxis • No further cases reported

  19. 10. Write report and disseminate findings • Numerous papers published on investigation

  20. Summary • Multi-state investigation • Involved local, state and federal agencies • Thousands of people potentially affected

  21. References and acknowledgments • Chin J. Control of communicable diseases manual. 2000. American Public Health Assoc, Washington, DC. p 20. • Dicker R. Principles of epidemiology: self-study guide. Public Health Training Network. Atlanta: Centers for Disease Control and Prevention. Available from: www.phppo.cdc.gov/PHTN//catalog/3030g.asp • Friis RH, Sellers TA. Epidemiology for public health practice. 1999. Aspen, Gaithersburg, MD. pp 52-53. • Jernigan DB, Raghunathan PL, Bell BP, Brechner R, Bresnitz EA, Butler JC, et al. Investigation of bioterrorism-related anthrax, United States, 2001: epidemiologic findings. Emerg Infect Dis [serial online]. 2002 Oct (cited 2005 Mar);8. Available from URL: http://www.cdc.gov/ncidod/EID/vol8no10/02-0353.htm • Slater MR. Veterinary epidemiology. 2003. Butterworth Heinemann, St. Louis, MO. p. • Dr. Paul E. Grunenwald, Harris County Public Health and Environment Services

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