Apply Basic Descriptive Statistics to Accurately Describe an Outbreak Event

1. Apply Basic Descriptive Statistics to Accurately Describe an Outbreak Event Sunpetch Angkititrakul, PhD. สรรเพชญ อังกิติตระกูล

3. Outbreak • the occurrence of more cases of disease than normally expected within a specific place or group of people over a given period of time

4. outbreak” and “epidemic • the same thing to an epidemiologist • “epidemic” has a more serious connotation than “outbreak” (mean+2SD) • Outbreaks threaten the fewest people • Chicken pox • Epidemics affect more people • SARS • pandemic is a global disease outbreak • HIV/AIDS 

5. การพิจารณาว่ามีโรคระบาดเกิดขึ้นหรือไม่ ความถี่ของโรคมากกว่าค่าเฉลี่ยบวก สองเท่าของความคลาดเคลื่อนมาตรฐาน (mean ± 2 S.D.)

6. Scope of outbreak investigation • Epidemiological investigation • Descriptive epidemiological investigation • Analytical epidemiological investigation • Environmental investigation • Laboratory investigation

7. Outbreak investigation • Confirm diagnosis • Outbreak verification • Identify cases • Descriptive epidemiology • time, place and animal • Develop hypothesis • Intensive follow-up • Share the result

8. Descriptive epidemiological investigation • Survey of disease data • Describe • person / animal • place • time

9. Survey of disease data • Incidence rate • Attack rate • Mortality rate

10. Descriptive epidemiological by time • Epidemic curve: a graphical depiction of the number of cases of illness by the date of illness onset • Pattern of spread • Magnitude • Outliers • Time trend • Exposure and/or disease incubation period

11. Classification of Epidemic Curves • Point source • Common source • Propagated

12. Point source • persons are exposed to the same exposure over a limited • defined period of time, usually within one incubation period • The shape of this curve commonly rises rapidly and contains a definite peak at the top, followed by a gradual decline.

13. Point source

14. Point source

15. Common source • exposure to the source is prolonged over an extended period of time and may occur greater than one incubation period • The down slope of the curve may be very sharp if the common source is removed

16. Common source

17. Common source

18. Propagated • source of infection for subsequent cases • The shape of the curve usually contains a series of successively larger peaks • person-to-person or animal-to animal contact

19. Propagated

20. Propagated

21. ชนิดของการระบาดของโรคชนิดของการระบาดของโรค 1. การระบาดของโรคจากแหล่งแพร่เชื้อร่วมกัน (Common-Source Epidemics) 2. การระบาดของโรคจากแหล่งแพร่เชื้อกระจาย(Propagated-Source Epidemics)

22. Common-Source Epidemics จำนวนสัตว์ เวลา

23. Propagated-Source Epidemics จำนวนสัตว์ เวลา

25. Descriptive epidemiological byplace • Spot map indicates the location of each case of a rare disease or outbreak by a place • relevant to the health event being investigated

26. Spot mapping (global)

27. Spot mapping(country)

28. John Snow

29. Cholera in London, 1854

30. Spot maps

32. Area maps

33. Descriptive epidemiologicalby person • How to distribution • Source of disease • Risk factors

35. Produce an Epidemic Curve • a graphical depiction of the number of cases of illness by the date of illness onset • histogram • a bar graph • a frequency polygon • The frequency of new cases is plotted on the vertical (y) axis, while the horizontal (x) axis has a time scale

36. Steps in Creating an Epidemic Curve • Identify the date of onset for the first case in the curve • Set the time interval • Create X-axis lead and end periods • Draw tick marks and label the time intervals

37. Steps in Creating an Epidemic Curve • Assign the area that is equal to one case on the Y-axis. • Plot the cases on the graph. • Mark the critical events on the graph and add graph labels.

38. When the Disease is Unknown • Lead and End Periods • When the incubation period is unknown, use 1 to 2 weeks for the lead and end periods • Time Intervals • If the disease is unknown, a good way to set the time interval is to create at least three epidemic curves, each with a different time interval. For our example, we use: 1 day, 4 days, and 1 week

39. Interpreting an Epidemic Curve • How an epidemic spread throughout a population; • At what point you are in an epidemic; • The diagnosis of the disease by establishing the potential incubation period.

40. Measure of descriptive statistics • Frequency • Mean, median and mode • Range, standard deviation, variance, correlation coefficient

41. X Y อัตราส่วน Ratios Ratios = X and Y can be any number, including ratios

42. X Δt อัตรา Rate Type of ratio where numerator is usually a count, and denominator is a time elapsed Rate=

43. a a + b สัดส่วน Proportion • Type of ratio where the numerator is part of the denominator Proportion =

44. a a + b Percent Percent = x 100 • Proportion multiple 100

45. สรุป • การอธิบายการเกิดโรคระบาดทางระบาดวิทยา • สัตว์ • สถานที่ • เวลา • การเก็บข้อมูล หลักฐานของการเกิดโรคระบาดให้ครบถ้วน ถูกต้อง เชื่อถือได้ • นำมาเขียนเป็นกราฟ เพื่อใช้ในการอธิบายการเกิดโรค

47. ขอบคุณครับ