3. Outbreak Investigation COL.POTE AIMPUN, MD., Dr.PH Medical Specialist Office for Medical Services Office of Permanent Secretary of Defense

8. Judged to be an outbreak A greater number of cases than normally occur in the same place compare to the same period of time

9. Meningococcal Epidemic Curve July '96 - June '98, Ireland

10. Judged to be an outbreak A cluster of cases which can be linked to the same exposure. The number of meningococcal cases associated with pilgrims who have traveled for the Haj has increased, and the total number of cases to date is 14 including 4 death Judged to be an outbreak A single case of disease that has never been occurred . A 3 year old boy, case of Avian flu (HSN1), alerted the public health people around the world to start a full scale investigation

13. Routine Surveillance Health personnel Laboratory General public Media Detection of Outbreak

33. Common source outbreak

34. Epidemic curve Sick date Exposure date Number of patients

36. Propagated source epidemics

37. Epidemic Curve Propagated source epidemics Sick date Number of patients

40. Compare Common Source Propagated source 1.Curve Bell curve Scatter bell 2.First and last pt. < 1 IP > 1 IP 3.Transmission One source From person to person 4.Duration Short Long 5. control Eradicate source Health education

45. Iceberg Phenomenon Hosp. visit w symptoms No symptoms Infected Risk Diagnosed

49. Sensitivity and specificity Sensitivity Specificity

50. Test result d c Negative b a Positive No Yes Disease

52. Test result d c Negative b a Positive No Yes Disease Sensitivity = P(T+|D+) = a /(a+c)

53. Test result d c Negative b a Positive No Yes Disease False-negative rate = P(T-|D+) = c/(a+c) TPF + FNF = 1

55. Test result d c Negative b a Positive No Yes Disease Specificity = P(T-|D-) = d /(b+d)

56. Test result d c Negative b a Positive No Yes Disease False-positive rate = P(T+|D-) = b/(b+d) TNF + FPF = 1

57. Test result 900 200 Negative 100 800 Positive No Yes Disease Specificity = 800/1000 = 0.8 Specificity = 900/1000 = 0.9 Accuracy = (800+900)/2000 = 0.85 1000 1000

61. Confirm outbreak and diagnosis Is this an outbreak? What is the diagnosis? Link between cases? Higher than expected? Clinical manifestation Laboratory result

63. Outbreak confirmed, further investigation warranted Form outbreak Investigation & control team Epidemiologist Microbiologist Clinician Environmentalist Government Media etc. Team coordinates Field investigation

64. 2. Define case and start case-finding 3. Descriptive data collection and analysis Descriptive epidemiology Person Place Time

65. Identify & count cases Obtain Information Identifying information Demographic data Clinical details Risk factors

68. Identify & count cases Obtain Information Orient cases in -Time -Place -Person Analysis of Descriptive data

70. Dz and rate of measles Age group ( year ) Number of pt. Medical personnel Attack rate (%) male female male female male female 20 - 24 0 1 0 6 0 16.67 25 - 29 0 3 8 29 0 10.34 30 - 34 2 2 8 22 25 9.09 35 - 39 0 1 1 11 0 9.09 40 – 44 0 1 4 4 0 25.00 45 – 49 0 0 3 0 0 0 50 + 0 0 3 2 0 0 Total 2 8 27 74 7.4 10.81

77. Cases Evaluate information Pathogen? Source? Transmission? Person Place Time Hypothesis setup : from all the data