Disease Outbreak Qinghai  Medical College Wang Zhaofen Oct,27,2005
Investigating an Outbreak---a Challenge for the  Disease  Detective 1.What is an outbreak? 2.Uncovering Outbreaks 3.Why In...
What Is an Outbreak? An outbreak, or an epidemic, exists when there are more cases of a particular disease: <ul><ul><li>1....
Requirements of a Disease Outbreak <ul><li>The presence of a pathogen in sufficient  quantities to affect multiple persons...
Pathogen Mode of Transmission Factors  required for the development and maintenance of a disease outbreak Fig.1
Mode of Transmission in  Acute Outbreak of Disease ★ Person – to – person ★ common-source exposure
Uncovering Outbreaks <ul><li>Health departments learn about most outbreaks in one of two ways: </li></ul><ul><ul><li>Calls...
Why Initiate an Investigation? <ul><ul><ul><li>Describe the problem  </li></ul></ul></ul><ul><ul><ul><li>Control and preve...
Whether an Investigation Is Warranted? ◇ Apparent number of persons affected ◇ Presence of unusual or severe clinical symp...
Guidelines for Epidemiologic Field Investigations <ul><li>Prepare for field work  </li></ul><ul><li>Verify diagnosis  </li...
Guidelines for Epidemiologic Field Investigations <ul><li>Tabulate and orient data: time, place,  </li></ul><ul><li>and pe...
Field Investigation: Time <ul><li>Epidemic curve: # of cases by time of  </li></ul><ul><li>onset </li></ul><ul><li>Shape o...
Field Investigation: Place <ul><li>Orient to:  </li></ul><ul><ul><li>place of residence  </li></ul></ul><ul><ul><li>place ...
Field Investigation: Person <ul><li>Thoroughly describe the case group  </li></ul><ul><li>(things such as age, sex, race) ...
What interventions could terminate an outbreak? ◆ Removal or elimination of the source of the  pathogen  ◆ Blockage of the...
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Outbreak of disease ---www

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  • I learned that a disease only effecting one group of people can be described as an acute outbreak and that two sources of the same disease can be different outbreaks
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Outbreak of disease ---www

  1. 1. Disease Outbreak Qinghai Medical College Wang Zhaofen Oct,27,2005
  2. 2. Investigating an Outbreak---a Challenge for the Disease Detective 1.What is an outbreak? 2.Uncovering Outbreaks 3.Why Investigate an Outbreak?
  3. 3. What Is an Outbreak? An outbreak, or an epidemic, exists when there are more cases of a particular disease: <ul><ul><li>1. in an area, </li></ul></ul><ul><ul><li>among a specific group of </li></ul></ul><ul><ul><li>people, or </li></ul></ul><ul><ul><li>3. over a particular period of time </li></ul></ul>
  4. 4. Requirements of a Disease Outbreak <ul><li>The presence of a pathogen in sufficient quantities to affect multiple persons </li></ul><ul><li>An appropriate mode of transmitting the pathogen to susceptible persons </li></ul><ul><li>An adequate pool of susceptible persons who are exposed to the pathogen . Fig.1 </li></ul>
  5. 5. Pathogen Mode of Transmission Factors required for the development and maintenance of a disease outbreak Fig.1
  6. 6. Mode of Transmission in Acute Outbreak of Disease ★ Person – to – person ★ common-source exposure
  7. 7. Uncovering Outbreaks <ul><li>Health departments learn about most outbreaks in one of two ways: </li></ul><ul><ul><li>Calls from a physician </li></ul></ul><ul><ul><li>or other healthcare </li></ul></ul><ul><ul><li>provider. </li></ul></ul><ul><ul><li>2. Public heath surveillance </li></ul></ul>
  8. 8. Why Initiate an Investigation? <ul><ul><ul><li>Describe the problem </li></ul></ul></ul><ul><ul><ul><li>Control and prevention </li></ul></ul></ul><ul><ul><ul><li>based on scientific evidence </li></ul></ul></ul><ul><ul><ul><li>Political and public concerns </li></ul></ul></ul><ul><ul><ul><li>Training of epidemiologists </li></ul></ul></ul><ul><ul><ul><li>Research--answer scientific </li></ul></ul></ul><ul><ul><ul><li>questions </li></ul></ul></ul>
  9. 9. Whether an Investigation Is Warranted? ◇ Apparent number of persons affected ◇ Presence of unusual or severe clinical symptoms ◇ Lack of an obvious explanation for disease occurrence ◇ Perceived need to implement control measures ◇ Level of public concern ◇ Potential for contributing to medical knowledge
  10. 10. Guidelines for Epidemiologic Field Investigations <ul><li>Prepare for field work </li></ul><ul><li>Verify diagnosis </li></ul><ul><li>Confirm epidemic </li></ul><ul><li>Identify and count cases </li></ul><ul><ul><li>create case definition </li></ul></ul><ul><ul><li>develop line listing </li></ul></ul>
  11. 11. Guidelines for Epidemiologic Field Investigations <ul><li>Tabulate and orient data: time, place, </li></ul><ul><li>and person </li></ul><ul><li>Take immediate control measures </li></ul><ul><li>Formulate and test hypothesis </li></ul><ul><li>Plan additional studies </li></ul><ul><li>Implement and evaluate control </li></ul><ul><li>measures </li></ul><ul><li>Initiate surveillance </li></ul><ul><li>Communicate findings </li></ul>
  12. 12. Field Investigation: Time <ul><li>Epidemic curve: # of cases by time of </li></ul><ul><li>onset </li></ul><ul><li>Shape of the curve gives you clues: </li></ul><ul><ul><li>agent known: use incubation period to </li></ul></ul><ul><ul><li>look back at exposure </li></ul></ul><ul><ul><li>agent unknown, but common event </li></ul></ul><ul><ul><li>likely: postulate agent by determining </li></ul></ul><ul><ul><li>the incubation period </li></ul></ul>
  13. 13. Field Investigation: Place <ul><li>Orient to: </li></ul><ul><ul><li>place of residence </li></ul></ul><ul><ul><li>place of work </li></ul></ul><ul><ul><li>activity sites (church, reunions, weddings, etc.) </li></ul></ul><ul><li>Spot map: specific residence and/or </li></ul><ul><li>exposure </li></ul><ul><ul><li>within buildings </li></ul></ul><ul><ul><li>city blocks or neighborhoods </li></ul></ul><ul><ul><li>county or state level </li></ul></ul>
  14. 14. Field Investigation: Person <ul><li>Thoroughly describe the case group </li></ul><ul><li>(things such as age, sex, race) </li></ul><ul><li>Identify things shared in common </li></ul><ul><li>(events, behaviors, etc.) </li></ul><ul><li>Get information on people who are </li></ul><ul><li>NOT cases as well - the population! </li></ul><ul><li>Compare groups </li></ul>
  15. 15. What interventions could terminate an outbreak? ◆ Removal or elimination of the source of the pathogen ◆ Blockage of the transmission process ◆ Elimination of susceptibility (eg, through vaccination or medication )
  16. 16. Thank you

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