Bài giảng Điều tra dịch - PGS.TS Lê Hoàng Ninh

Nội dung text: Bài giảng Điều tra dịch - PGS.TS Lê Hoàng Ninh

1. ÑÑIEIEÀUÀU TRATRA DÒCHDÒCH PGS,PGS, TSTS LEÂLEÂ HOAHOAØNGØNG NINHNINH 1
2. MUMUÏCÏC TIEÂUTIEÂU BABAØIØI HOHOÏCÏC • 1. Ñònh nghóa caùc töø : • Dòch, ca leû teû, beänh löu haønh ñòa phöông, ñaïi dòch • 2. Lieät keâ caùc böôùc tieán haønh ñieàu tra dòch • 3. Vôùi moät soá thoâng tin cho saún, thöïc hieän caùc böôùc ñieàu tra, phaùt trieån giaû thuyeát • 4. Tính caùc soá ño veà söï lieân quan trong tieán haønh ñieàu tra dòch 2
3. PHAPHAÙTÙT HIEHIEÄNÄN SSÖÏÖÏ BUBUØNGØNG PHAPHAÙTÙT DÒCHDÒCH • 1. Qua döõ lieäu/ soá lieäu thu thaäp routine • 2. Phaân tích theo thôøi gian, khoâng gian phaùt hieän ra soá ca taêng leân hay moät cluster ca beänh baát thöôøng • 3. Qua caùc tröôøng hôïp baùo caùo ca beänh haøng tuaàn hay qua caùc thoâng tin veà tieáp xuùc cuûa caùc ca beänh. • 4. Nhaân vieân y teá. 3
4. LYLYÙÙ DODO PHAPHAÛIÛI ÑÑIEIEÀUÀU TRATRA DÒCHDÒCH 1. Kieåm soaùt/ phoøng choáng 2. Cô hoäi nghieân cöùu 3. Huaán luyeän ñaøo taïo 4. Vaán ñeà coâng coäng, chính trò, kinh teá xaï hoäi 5. Chöông trình y teá 4
5. BaBaøiøi tataäpäp Trong naêm 2005, taïi moät xaõ coù 9 cö daân cheát do ung thö voøm haàu, anh chò haõy lieät keâ caùc lyù do ñieàu tra xaùc ñònh dòch? 5
6. ÑÑIEIEÀUÀU TRATRA MOMOÄTÄT VUVUÏÏ DÒCH:DÒCH: 1010 BBÖÖÔÔÙCÙC 1. Prepare for field work 2. Establish the existence 3. Vierify the diagnosis 4. Define and identify cases • A) case definition • B) identify and count cases 5. Perform descriptive Epid. 6. Develop hypothesis 6
7. ÑÑIEIEÀUÀU TRATRA MOMOÄTÄT VUVUÏÏ DÒCH:DÒCH: 1010 BBÖÖÔÔÙCÙC (( TT)TT) 7. Evaluate hypothesis 8. If necessary, reconsider/ refine hypothesis and execute additional studies a) additional epid. Studies b) other types of studies- lab, environment 9. Implement control and prevention measures 10. Communicate findings 7
8. ÑÑIEIEÀUÀU TRATRA MOMOÄTÄT VUVUÏÏ DÒCH:DÒCH: 1010 BBÖÖÔÔÙCÙC • Baøi taäp 2: – Trong 10 böôùc naày, theo anh chò böôùc naøo laø quan trong nhaát ? – Khi ñieàu tra dòch coù caàn tuaân thu theo thöù töï ñuû 10 böôùc treân khoâng? 8
9. BBÖÖÔÔÙCÙC 1:1: PREPARINGPREPARING FORFOR FIELDFIELD WORKWORK • 3 NHOÙM COÂNG VIEÄC: – INVESTIGATION: » KNOWLEGDE: COÙ/ KHOÂNG COÙ, BOÄ CAÏU HOÛI MAÃU » SUPPLIES, EQUIMENT: LAB. MATERIALS, COMPUTER, CAMERA, OTHERS – ADMINISTRATION: » ADMINISTRATION PROCEDURES – CONSULTATION » YOUIR EXPECTED ROLE IN THE FIELD » WHO, WHERE, WHEN YOU ARE MEET AND CONTACT 9
10. BBÖÖÔÔÙCÙC 1:1: PREPRARINGPREPRARING FORFOR FIELDFIELD WORKSWORKS BAØI TAÄP: Ngaøy 28 thaùng 12 naêm 2005, ttytdp Cöûu long baùo moät vuï dòch 20 ngöôøi maéc beänh tieâu chaûy caáp phaûi nhaäp vieän. Anh chi haõy chuaån bi cho chuyeán di dieâu tra, phong chong dòch taïi ñaây. 10
11. BBööôôùcùc 2:2: thethe existenceexistence ofof anan outbreak?outbreak? - Epidemic: more cases of disease than expected in a given area/ group people / period of time 1. Sporadic 2. Endemic 3. Epidemic 4. pandemic - Cluster : aggregation of cases / given area/ particular period 11
12. BBÖÖÔÔÙCÙC 2:2: EXISTENCEEXISTENCE OFOF OUTBREAKOUTBREAK BAØI TAÄP 3: Vaøo thaùng 2 naêm 2006, trung taâm y teá döï phoøng tænh kieân giang baùo caùo leân tuyeán treân 24 ca bò hoiä chöùng vieâm naõo. Sau ñoù Vieän pasteur thaønh phoá xaùc ñònh laø do enterovirus 71. Theo anh chò ñaây coù phaûi laø vuï dòch? Vaø caùc böôùc chuaàn bò ñieàu tra dòch cuûa anh chò nhö theá naøo, neáu anh chò ñöôïc cöû tham gia vaøo ñoäi choáng dòch cuûa Vieän 12
13. BBÖÖÔÔÙCÙC 3:3: VERYFYINGVERYFYING THETHE DIASGNOSISDIASGNOSIS • Goal: – a) ensure the problem has been properly diagnosed – b) rule out lab. Error • Verifying: – Clinical review – Lab. Test • Recommendations: – Summarize clinical findings ( frequency distribution) – Visit several patients 13
14. BBÖÖÔÔÙCÙC 4a:4a: CASECASE DEFINITIONDEFINITION • Case definition: – Standard set of criteria for deciding – Including: clinical criteria, restrictions by time, place, person – Exam: clinical criteria on simple and objective measures: fever > 101 F ( degree), three or more loose movement per day, person onset within 2 weeks, resident of the nine county area, to person who no previous history of . You must apply them them consistently and without bias to all person under investigation 14
15. BBÖÖÔÔÙCÙC 4a:4a: CASECASE DEFINITIONDEFINITION (( tttt)) • Case definition: – Include most if not all of actual cases – None or few of what are “ false-positive cases” – Ofcourse, to be classified as confirmed, must have lab. Verification. – Investigators can define cases in the following 3 classes: EX: bloody diarr. And hemolytic- uremic syndrome caused by E. coli O 157: H7 • Definite case: • Probable case: bloody diarrhea, same person, place, time restriction • Possible case: Abdominal cramp and diarrhea ( at least 24 –hour period in school –age child with onset during the same period) 15
16. BBÖÖÔÔÙCÙC 4b:4b: IdentifyingIdentifying andand countingcounting casescases • Determine the geographic extent of problem and the pop. affected by it. • To identify cases, use many sources you can: • Physician offices • Clinics • Hospitals • Health station • Ask patients • Survey 16
17. BBÖÖÔÔÙCÙC 4b:4b: identifyingidentifying andand countingcounting casescases • Types of information / every cases: • Identifying information • Demographic information • Clinical information • Risk factor information • Reporter information • Report forms, questionnaires, data forms 17
18. BBÖÖÔÔÙCÙC 4b:4b: identifyingidentifying andand countingcounting casescases • Trong moät vuï dòch tieân chaûy caáp xaûy ra vaøo thaùng 12 naêm 2005 taïi xaõ x, y, z huyeän mang thít tænh vónh long. Anh chi hay giuùp nhaân vieân y teá tuyeán döôùi thieát keá caùc forms thu thaäp thoâng tin veà caùc tröôøng hôïp beänh. 18
19. BBööôôùcùc 5:5: PerformingPerforming descriptivedescriptive EpidEpid • 1. Looking at data carefully to become familiar with them to learn what information is reliable and informative or not be as reliable • 2. Comprehensive description: •Place •Time •who – what is known about the disease: usual source, mode of transmission, risk factors, pop. affected: – Develop hypothesis 19
20. BBööôôùcùc 5:5: performingperforming DescriptiveDescriptive epidemic.(epidemic.( tttt)) • Time: – an epidemic curve • Tell you where you are in the time course of an epid. • What the future course might be • Know a probable time period of exposure-Æ focussing exposure at that time • Epidemic pattern – Draw epidemic curve: • Unit of time on x –axis, 1/8 to 1/3 as long as incubation period • Draw several epidemic curve to find the best 20
21. BBööôôùcùc 5:5: performingperforming DescriptiveDescriptive epidemic.(epidemic.( tttt)) • Interpreting epidemic curve: – Epidemic pattern – Incubation: max, average, min – A point source epidemic in which persons are exposed to the same source over relative brief period: suggest sudden expose to a common source .If duration of exposure was prolonged, call a continuous common source epidemic – If person to person spread- a propagated epidemic- should have a series of progressively taller peaks 21
22. BBööôôùcùc 5:5: performingperforming DescriptiveDescriptive epidemic.(epidemic.( tttt)) • To identify the likely period of exposure: – Look up the average and minimum incubation periods – Identify the peak of outbreak/ median case and count back on the x one average incubation period • NOTE THE DATE – Start at the earliest case of the epidemic and count back the minimum incubation period • NOTE THIS DATE 22
23. BBööôôùcùc 5:5: performingperforming DescriptiveDescriptive epidemic.(epidemic.( tttt)) • Bai tap: • Dung so lieu tu vu dich do viem gan A. Tu duong cong dich ma ban ve duoc va nhung kien thuc cua ban ve thoi gian u benh trung binh va toi thieu, ban hay xac dinh thoi gian tiep xuc cua cac ca benh. ( p 369) 23
24. BBööôôùcùc 5:5: performingperforming DescriptiveDescriptive epidemic.(epidemic.( tttt)) • Place: • Spot map: – Geographic extent problem – Important etiologic clues – Where cases live, work, may have been exposed. 24
25. BBööôôùcùc 5:5: performingperforming DescriptiveDescriptive epidemic.(epidemic.( tttt)) • Person: – What populations are at risk – Host characteristics: •Age • Race •Sex • Medical status • Occupation • Leisure activities • Other behaviors: thuoc, an uong, sinh hoat 25
26. BuocBuoc 6:6: DevelopingDeveloping HypothesesHypotheses • Hypotheses should include; – Source of agent – Mode of transmission – Exposures • Generate hypotheses: many ways: – What you know about disease – Agent’s reservoir – How is it usually transmitted? – What vehicles are common implicated – What are the known risk factors – Round up the usual suspects – Talk to case-patient – Descriptive epidemiology – . 26
27. BuocBuoc 77 :: EvaluatingEvaluating HypothesesHypotheses • 2 ways to evaluate in the field investigation: – Comparing the hypotheses with the established fact: » Clinical, »Lab., » Environmental, » Epidemic evidences are clear – Using analytic epidemiology: » Comparison group » Cases series of cases is insufficient for testing hypotheses » 2 types of studies to test hypotheses: cohort and case- cotrol 27
28. BuocBuoc 77 :: EvaluatingEvaluating HypothesesHypotheses (*(* tttt)) • Cohort studies: – The best for outbreak a small, well defined population. EX. Gastroenteritis among persons who attended a wedding. – Measure the relationship between risk factor and disease: Relative risk ( RR) • RR = a / (a +b) / c / ( c + d) – Testing of statistical significance: chi-square, p value 28
29. BuocBuoc 77 :: EvaluatingEvaluating HypothesesHypotheses (*(* tttt)) – Testing of statistical significance: chi-square, p value: – Two-by-two table: • a + b + c + d = T • a + b = H1 ; c + d = H2 ab • a + c = V 1 ; b +d = V2 • Chi-square = cd • T [{ ad –bc} – T/2] 2 • • V1 V2 H1 H2 • If smaller studies, use Fisher exact test 29
30. BuocBuoc 77 :: EvaluatingEvaluating HypothesesHypotheses (*(* tttt)) • Case – control studies: – the population is not well defined – Are more common than cohort studies – Association measure : Odds ratio (* OR ) » OR = a.d / b.c – Control group: » A random sample from healthy population » Other common groups : neighbors , friends, patients from the same physician practice or hospital – Test of statistical significance = Chi-squares 30
31. BuocBuoc 77 :: EvaluatingEvaluating HypothesesHypotheses (*(* tttt)) • Bai tap: • Ban duoc yeu cau giup dieu tra mot chum 17 benh nhan mac benh ung thu bach cau. Trong so hoï co mot so ngö8oi lam nghe sua chua dien tu, so con lai lam trong xuong lap rap radio. Loai hinh thiet ke nao duoc chon de tien hanh khao sat su lien quan giua lanh vuc dien tu va benh ung thu bach cau? 31
32. BuocBuoc 77 :: EvaluatingEvaluating HypothesesHypotheses (*(* tttt)) • Mot nghien cvöùu ve tinh trang phat ban trong cong nhan xu8ong lam banh keo, nguoi ñ8ieu tra dung thiet ke cohort study de tien hanh dieu tra. Bang duoi day trinh bay so lieu ve tiep xuc voi chat celery. Theo anh chi so do nao la phu hop giup do luong su lien quan va tinh so do nay?. Tinh chi-square of test statistical significance ? Ban ly giai ket qua nay nhu the nao ? 32
33. BuocBuoc 88 :: refininrefiningg hhyypothesespotheses andand executinexecutingg additionaladditional studiesstudies • Epidemiologic studies: – If you can not generate good hypotheses, then proceeding to analytic epidemiology, is likely to be a waste of time – When analytic epidemiology is unrevealing: reconsider hypotheses – When your analytic studies identifies an association: refine your hypotheses to obtain more specific exposure histories, more specific control group to test more specific hypotheses – To expand our knowledge – outbreak is, may provide an experiment of nature 33
34. BuocBuoc 88 :: refininrefiningg hhyypothesespotheses andand executinexecutingg additionaladditional studiesstudies • Laboratory and environmental studies: – Laboratory evidence can clinch the finding – Environmental studies help in explaining why an outbreak occured 34
35. BuocBuoc 9:9: ImplementinImplementingg controlcontrol andand preventionprevention measuresmeasures • Primary goal is to control and prevent the outbreaks • You should implement control measures as soon as possible • You can implement control measures early if you know the source of an outbreak • In general, you aim control measures at the weak link or links in the chain of infection: specific agent, source or reservoir • You might direct control measures at interrupting transmission or exporure, at reducing the susceptibility of the host. 35
36. BuocBuoc 10:10: CommunicatingCommunicating thethe findingsfindings • Communication : 2 forms – An oral briefing for local authorities • Present your finding in clear and convincing fashion with appropriate recommendations • Present your finding in scientifically objective fashion and should be able to defend your conclutions and recommendations – A written report • The usual scientific format • A blueprint for action • A document for potential legal issues 36