Presentation is loading. Please wait.

Presentation is loading. Please wait.

Outbreak Investigation EPIET Introductory course 2006 Lazareto, Menorca, Spain.

Similar presentations


Presentation on theme: "Outbreak Investigation EPIET Introductory course 2006 Lazareto, Menorca, Spain."— Presentation transcript:

1 Outbreak Investigation EPIET Introductory course 2006 Lazareto, Menorca, Spain

2 What is an outbreak ? Occurrence of more cases of disease than expected –in a given area –over a particular period of time –among a specific group of people

3 Why investigate outbreaks? Stop the outbreak Understand what happened and why Prevent future outbreaks Improve our knowledge Improve surveillance and outbreak detection Training

4 Objectives for this session Describe –the principles of outbreak investigation –the steps in outbreak investigation Using practical examples –Outbreak of Hepatitis A in Ibiza, Spain September January 2001 Tomorrow –some operational and logistical aspects of outbreak investigation

5 Epidemiology Food safety Clinicians Laboratory Media Authorities Diagnostic Clinical Specimen transfer DeadSick Exposed SurveillanceInvestigation Prediction Supply channels Trace back Decisions Infrastructure Regulations Vaccinations etc Vector Reservoir Investigation Co-ordination

6 Specific demands when investigating outbreaks Unexpected event Act quickly Rapid control Interdisciplinary coordination Work carried out in the field Systematic approach

7 Outbreak of Hepatitis A in Ibiza (Spain) 2000/2001 Ibiza is a major tourist destination (2 million visitors in 2000) October 2000: 5 cases of Hepatitis A notified to local health authorities in Ibiza 3 cases of Hepatitis A among German tourists returning from Ibiza

8 Steps of an outbreak investigation Confirm outbreak and diagnosis Form Outbreak Control Team Define a case Identify cases and obtain information Describe data by time, place, person Develop hypothesis Test hypothesis: analytical studies Additional studies Communicate results: –outbreak report, publication Implement control measures Control measures

9 Detection Routine surveillance Clinical / Laboratory General public Media

10 2002 (n=184) (n=153) 2003 (n=150) Notified cases of S. Bovismorbificans, Germany

11 Confirm outbreak Is this an outbreak? More cases than expected? Surveillance data Surveys: hospitals, labs, physicians Caution! Seasonal variations Notification artefacts Diagnostic bias (new technique) Diagnostic errors (pseudo-outbreaks)

12 Outbreak of Hepatitis A in Ibiza, Spain Hepatitis A notifiable disease in Spain notifications in Ibiza during previous years: –1997: 6 cases –1998: 0 cases –1999: 4 cases

13 Confirm diagnosis Laboratory confirmation –serology –isolates, typing of isolates –toxic agents Meet attending physicians Examine some cases Contact (visit) the laboratories Not always necessary to confirm all the cases but confirm a proportion throughout the outbreak

14 Outbreak confirmed Immediate control measures? Further investigation? - prophylaxis - exclusion / isolation - public warning - hygienic measures - others - aetiological agent - mode of transmission - vehicle of transmission - source of contamination - population at risk - exposure causing illness

15 Epidemiologist Microbiologist Clinician Environmentalist Engineers Veterinarians Others Team coordinates field investigation Outbreak confirmed, further investigations warranted Form Outbreak Control Team

16 Descriptive epidemiology - Who are the cases? (person) - Where do they live? (place) - When did they become ill? (time)

17 Case definition Standard set of criteria for deciding if a person should be classified as suffering from the disease under investigation Criteria –clinical and/or biological criteria, –time –place –person

18 Case definition Simple, practical, objective Sensitive? Specific? Multiple case definitions –confirmed –probable –possible

19 Case definition Outbreak of Hepatitis A in Ibiza 2000/2001 Any person with IgM antibodies to Hepatitis A Virus August January 2001 on the island of Ibiza for at least one day during a day period before onset of illness or seroconversion

20 Identify & count cases notifications hospitals, GPs laboratories schools workplace, etc

21 Case-finding Outbreak of Hepatitis A in Ibiza 2000/2001 Contacting clinicians and laboratories on the island Note in German Epidemiological Bulletin Enquiries through European network

22 Identify & count cases Obtain information Identifying information Demographic information Clinical details Exposures and known risk factors

23 Obtaining information Outbreak of Hepatitis A in Ibiza 2000/2001 Trawling questionnaire Place and time of stay on Ibiza Food histories: –What eaten –Where bought? –Visit to restaurants

24 Organize information: Line list Names Date of birth Addresse Onset of symptoms Treating physician Hospital stay Laboratory results

25 Line List Case No. Name Date of birth Addresse Date of onset Lab results XY AB CD …

26 Identify & count cases Obtain information Analysis of descriptive data Describe in - time - place - person

27 Time: Epi Curve Histogram Distribution of cases by time of onset of symptoms, diagnosis or identification –time interval depends on incubation period Cases Days

28 Epi curve Describe –start, end, duration –peak –importance –atypical cases Helps to develop hypotheses –incubation period –etiological agent –type of source –type of transmission –time of exposure Cases Days

29 Examples of Epicurves hours cases days weeks Common point source Common persistent source Propagated source cases days Common intermittent source

30 Cases of Hepatitis A in Ibiza by week of onset, 2000/2001

31 Estimation of time or period of exposure max incubation min cases exposure

32 Outbreak of typhoid fever, Germany 2004

33 Place Place of residence Place of possible exposure –work –meals –travel routes, –day-care –leisure activities Maps –identify an area at risk

34 Cases of Hepatitis A in Ibiza by place of residence, 2000/2001 Portinatx Ibiza-City 10 km

35 Person Distribution of cases –age –sex –occupation, etc Distribution of these variables in population Attack rates

36 Outbreak of S. Agona, Germany

37 Cases of Hepatitis A in Ibiza by age group, 2000/2001

38 Develop hypotheses - Who is at risk of becoming ill? - What is the disease? - What is the source and the vehicle? - What is the mode of transmission?

39 exploratory interviews among cases of Hepatitis A, Ibiza 2000/01 3 potential risk factors: –visited a restaurant in the harbour of Ibiza town –bought food at a supermarket in the centre of the town –stayed at Hotel in Portinatx (German tourists)

40 Compare hypotheses with facts Test specific hypotheses Analytical studies - cohort studies - case-control studies

41 Testing hypothesis Cohort -attack rate exposed group -attack rate unexposed group Case control -proportion of cases exposed -proportion of controls exposed

42 Case-control study Outbreak of Hepatitis A in Ibiza 2000/2001 among residents of the island one control per case selected from the data-base of the health registration card matching for age and neighbourhood no history of hepatitis A disease or vaccination.

43 Cases of Hepatitis A and controls by exposure to restaurant and shop, Ibiza 2000/2001 ExposureCases (n=38) Controls (n=38) matched OR 95% CI Restaurant22 (57.9%)5 (13.2%) Shop13 (34.2%)6 (15.8%)

44 Cases of Hepatitis A and controls by exposure to food items, Ibiza 2000/2001 Restaurant Cases n = 22 Controls n = 5 Matched OR95% CI Salad180undef. Shopn = 13n = 6 Sausages Meat Vegetables Fish Bread

45 Verify hypothesis Additional investigations Microbiological investigation of food samples Environmental investigation Veterinarian investigation Molecular Typing Trace back investigations (origin of foods) Meteorological data Entomological investigations

46 Viral genome sequencing Outbreak of Hepatitis A in Ibiza 2000/2001 Alignment of aminoterminal region of VP3 38 serum samples Positive in 11 cases: –belonging to the three different groups –100% homology

47 Food trace-back NL Outbreak of S. Bovismorbificans, Germany 2004

48 Implement control measures 1) Control the source of pathogen 2) Interrupt transmission 3) Modify host response May (must) occur at any time during the outbreak!! At first, general measures According to findings, more specific measures

49 Recommendations Outbreak of Hepatitis A in Ibiza 2000/2001 Emphasise hygiene amongst food handlers Strengthen surveillance for foodborne diseases Enhance international co-operation

50 Outbreak report Regular updates during the investigation Detailed report at the end –communicate public health messages –influence public health policy –evaluate performance –training tool –legal proceedings

51 Steps of an outbreak investigation Confirm outbreak and diagnosis Form Outbreak Control Team Define a case Identify cases and obtain information Describe data by time, place, person Develop hypothesis Test hypothesis: analytical studies Additional studies Communicate results: –outbreak report, publication Implement control measures

52 The reality…. Info: Outbreak suspected time Confirmation Form Outbreak Control Team Confirm Diagnosis Site visit Case definition Line list Organize Data Descripitve Epidemiology Control measures Analytic Epidemiology Recommendations Report Publication


Download ppt "Outbreak Investigation EPIET Introductory course 2006 Lazareto, Menorca, Spain."

Similar presentations


Ads by Google