Dịch (epidemic) hay còn gọi là bùng phát (outbreak) khi số ca bệnh cao hơn số dự kiến xảy ra (trị số bình thường) tại một địa phương, khu vực nào đó, hay trên một nhóm dân số nào đó trong một thời khoảng nhất định. Bài giảng Điều tra vụ bùng phát bệnh từ thực phẩm giúp người học nắm được khái niệm, vai trò điều tra bùng phát,...Mời bạn đọc cùng tham khảo.
Điều Tra Vụ bùng phát bệnh từ thực phẩm GS, Ts Lê Hồng Ninh Bùng phát ?(outbreak) Dịch ( epidemic) hay gọi bùng phát ( outbreak)khi số ca bệnh cao số dự kiến xảy ( trị số bình thường) địa phương, khu vực đó, hay nhóm dân số thời khoảng định Epidemiology (Schneider) Số ca bệnh Bệnh lưu hành địa phương (endemic)và dịch ( epidemic) Lưu hành Thời gian Epidemiology (Schneider) Dịch Tại phải điều tra bùng phát/ dịch? Kiểm soát phịng ngừa Sự ác tính nguy lây truyền cho người khác Cơ hội nghiên cứu để hiểu biết tốt Cơ hội đào tạo Xem xét chương trình y tế Cab quan ngại khác: luật, trị, cơng cộng… Epidemiology (Schneider) Step 1: Verify the outbreak Determine whether there is an outbreak – an excess number of cases from what would be expected Establish a case definition Clinical / diagnostic verification Non-ambiguous Person / place / time descriptions Identify and count cases of illness Epidemiology (Schneider) Step 2: Plot an Epidemic Curve Graph of the number of cases (y-axis) by their date or time of onset (x-axis) Interpreting an epidemic curve Overall pattern: increase, peak, decrease Type of epidemic? Incubation period? Outliers: Early or late exposure? Epidemiology (Schneider) Unrelated? Index case? Secondary cases? Vector-borne Disease • Starts slowly • Time between the first case and the peak is comparable to the incubation period • Slow tail Point Source Transmission • This is the most common form of transmission in foodborne disease, in which a large population is exposed for a short period of time Continuing Common Source or Intermittent Exposure • In this case, there are several peaks, and the incubation period cannot be identified Salmonellosis in passengers on a flight from London to the United States, by time of onset, March 13 14, 1984 Source: Investigating an Outbreak, CDC The supper was held in the basement of the village church Foods were contributed by numerous members of the congregation The supper began at 6:00 PM and continued until 11:00 PM Food was spread out upon a table and consumed over a period of several hours Epidemiology (Schneider) Church Supper Menu Main Dishes • • • • • Baked ham Spinach Mashed potatoes Cabbage salad Fruit Salad Side Dishes • • • Jello Rolls Brown Bread Desserts • • • Cakes Vanilla Ice Cream Chocolate Ice Cream Beverages • • • Milk Coffee Water Epidemiology (Schneider) Which menu item(s) is the potential culprit? To find out, calculate attack rates The foods that have the greatest difference in attack rates may be the foods that were responsible for the illness Epidemiology (Schneider) Attack Rates by Items Served: Church Supper, Oswego, New York; April 1940 Number of persons who ate specified item Well Total Attack rate (%) 17 46 Number of persons who did not eat specified item Baked ham Ill 29 Spinach 26 17 43 20 12 32 Mashed potato 23 14 37 23 14 37 Cabbage salad 18 10 28 28 19 47 Jello 16 23 30 22 52 Rolls 21 16 37 25 13 38 Brown bread 18 27 28 20 48 Milk 2 44 27 71 Coffee 19 12 31 27 17 44 Water 13 11 24 33 18 51 Cakes 27 13 40 19 16 35 Ice cream (van) 43 11 54 18 21 Ice cream (choc) 25 22 47 20 27 Fruit salad 42 27 69 Epidemiology (Schneider) Ill 17 Well 12 Total 29 Attack rate % Attack Rates by Items Served: Church Supper, Oswego, New York; April 1940 Number of persons who ate specified item Number of persons who did not eat specified item Baked ham Ill 29 Well 17 Total 46 Attack rate (%) 63 Ill 17 Well 12 Total 29 Attack rate % 59 Spinach 26 17 43 60 20 12 32 62 Mashed potato 23 14 37 62 23 14 37 62 Cabbage salad 18 10 28 64 28 19 47 60 Jello 16 23 70 30 22 52 58 Rolls 21 16 37 57 25 13 38 66 Brown bread 18 27 67 28 20 48 58 Milk 2 50 44 27 71 62 Coffee 19 12 31 61 27 17 44 61 Water 13 11 24 54 33 18 51 65 Cakes 27 13 40 67 19 16 35 54 Ice cream (van) 43 11 54 80 18 21 14 Ice cream (choc) 25 22 47 53 20 27 74 Fruit salad 67 42 27 69 61 Attack Rates by Items Served: Church Supper, Oswego, New York; April 1940 Number of persons who ate Ill specified item Well Total Attack rate (%) Number of persons who did not eat specified item Ill Well Total Attack rate % Baked ham 29 17 46 63 17 12 29 59 Spinach 26 17 43 60 20 12 32 62 Mashed potato 23 14 37 62 23 14 37 62 Cabbage salad 18 10 28 64 28 19 47 60 Jello 16 23 70 30 22 52 58 Rolls 21 16 37 57 25 13 38 66 Brown bread 18 27 67 28 20 48 58 Milk 2 50 44 27 71 62 Coffee 19 12 31 61 27 17 44 61 Water 13 11 24 54 33 18 51 65 Cakes 27 13 40 67 19 16 35 54 Ice cream (van) 43 11 54 80 18 21 14 Ice cream (choc) 25 22 47 53 20 27 74 Fruit salad 67 42 27 69 61 Highlighted row indicates largest difference between attack rates Attack Rate by Consumption of Vanilla Ice Cream, Oswego, New York; April 1940 Ill Total Yes 43 11 54 79.6 No 18 21 14.3 Total Ate vanilla ice cream? Well Attack Rate (%) 46 29 75 61.3 • The relative risk is calculated as 79.6/14.3 or 5.6 • The relative risk indicates that persons who ate vanilla ice cream were 5.6 times more likely to become ill than those who did not eat vanilla ice cream Conclusion An attack of gastroenteritis occurred following a church supper at Lycoming The cause of the outbreak was most likely contaminated vanilla ice cream Epidemiology (Schneider) Surveillance Ongoing systematic collection, collation, analysis and interpretation of data; and the dissemination of information to those who need to know in order that action may be taken World Health Organization Epidemiology (Schneider) Purposes of Public Health Surveillance Estimate magnitude of the problem Determine geographic distribution of illnesses Portraying the natural history of disease Detect epidemic / Define a problem Generate hypotheses and stimulate research Evaluate control measures Monitor changes in infectious agents Detect changes in health practice Facilitate planning CDC Epidemiology (Schneider) Passive Surveillance Physicians, laboratories, and hospitals are given forms to complete and submit with the expectation that they will report all of the cases of reportable disease that come to their attention Advantages: Inexpensive Disadvantages: Data are provided by busy health professionals Thus, the data are more likely to be incomplete and underestimate the presence of disease in the population Epidemiology (Schneider) Active Surveillance Involves regular periodic collection of case reports by telephone or personal visits to the reporting individuals to obtain the data Advantages: More accurate because it is conducted by individuals specifically employed to carry out the responsibility Disadvantages: Expensive Epidemiology (Schneider) Sentinel Surveillance Monitoring of key health events, through sentinel sites, events, providers, vectors/animals Case report indicates a failure of the health care system or indicates that special problems are emerging Advantages: Very inexpensive Disadvantages: Applicable only for a select group of diseases Epidemiology (Schneider) Some Surveillance Programs National Notifiable Diseases Surveillance System http://www.cdc.gov/epo/dphsi/nndsshis.htm Morbidity and Mortality Weekly Report (MMWR) http://www.cdc.gov Cancer Surveillance, Epidemiology and End Result (SEER) http://www.seer.cancer.gov/ Epidemiology (Schneider) “Good surveillance does not necessarily ensure the making of right decisions, but it reduces the chances of wrong ones.” Alexander D Langmuir NEJM 1963;268:182-191 Epidemiology (Schneider) ... Epidemiology (Schneider) Số ca bệnh Bệnh lưu hành địa phương (endemic)và dịch ( epidemic) Lưu hành Thời gian Epidemiology (Schneider) Dịch Tại phải điều tra bùng phát/ dịch? Kiểm sốt phịng ngừa.. .Bùng phát ?(outbreak) Dịch ( epidemic) hay cịn gọi bùng phát ( outbreak)khi số ca bệnh cao số dự kiến xảy ( trị số bình thường) địa phương,... the peak is comparable to the incubation period • Slow tail Point Source Transmission • This is the most common form of transmission in foodborne disease, in which a large population is exposed