1. Priority Setting for Food Borne Pathogens Angela Vargas Supervisors: Dr. Arie Havelaar Prof. Dr. Roger Cooke 12, June 2007 TU Delft

2. Overview Introduction Problem Description Methodology Paired Comparisons Probabilistic Inversion Elicitation and Analysis Results Conclusions and Recommendations

3. Introduction Disease Burden YLD Years Lived with a Disability YLL Years of Live Lost DALY Disability-Adjusted Life Years Cost-of-illness COI Cost-of-illness DHC Direct Health care Costs DNHC Direct Non-health care Costs INHC Indirect Non-health care Costs Fraction of cases attributable to Food Fraction of cases attributable to Food Group

4. Pathways Food borneEnvironmentalHuman-humanDirect animalTraveling

5. Food borne Transmission through food that is contaminated when it enters the kitchen or during preparation (e.g. by food handlers). Environmental Transmission through contaminated water (drinking water, recreational water), soil, air or other environmental media. Human-humanTransmission from person to person by the fecal-oral route. Direct animal Transmission by direct contact with live animals including pets, farm animals, petting zoos etc. Abroad Cases when exposure takes place by any of the above pathways during foreign travel. Pathways Description

6. Food Categories Beef and lamb Pork Chicken and other poultry Eggs Dairy products Fish and shellfish Fruit and vegetables Beverages Bread, grains, pastas and bakery products Other foods incl. composite foods Infected humans or animals Food Categories

7. Problem Description Determine the fraction of transmission route for each pathogen and the fraction of transmission due to specific food groups. The objective is to find a fast, not resource intensive and accurate method of estimation for these fractions. Estimated fractions that will sum to one Insufficient data

8. Methodology Paired Comparisons Compare pair wise of all items in order to determine preference. The result is a score for each item. Lighter elicitation for experts. The resulting scores sum to one. Probabilistic Inversion Experts give quantiles for the query variables. It is possible to estimate results that sum up to one. …

9. Paired Comparisons 1000 0 000 1 1 11 110 0 1 101

10. Paired Comparisons Results Item nameScoreConf L.Conf U. Food Ingestion0.95570.83350.9978 Environment0.01230.00030.0528 Contact with sick person0.00150.00000.0054 Direct animal contact0.00460.00010.0145 Contamination abroad0.02590.00100.1058

11. Paired Comparisons Results Item nameScoreConf L.Conf U. Beef and lamb0.05240.01890.1079 Pork0.16010.06320.2745 Chicken and poultry0.29090.16190.4658 Eggs0.44920.27560.6481 Dairy products0.00980.00160.0211 Fish and shellfish0.00690.00120.0163 Fruit and vegetables0.00610.00130.0148 Beverages0.00120.00010.0029 Bread, grains, pasta0.00230.00030.0049 Composite Foods0.01180.00260.0251 Food Handlers0.00930.00150.0195

12. Probabilistic Inversion BACK u1u2 0.110.89 0.190.81 0.830.17 0.120.88 0.310.69 0.110.89 0.730.27 0.590.41 0.770.23 0.940.06 0.730.27 0.150.85 1 1 1 1 1 1 1 1 1 1 1 1 00.160.15 0.130.220.12 0.100.140 0.31 0.46 0.24 0.220.510.26

13. IPF – One iteration 00.250.02 0.380.03 0.270 0.050.90.05 0.268 0.430 0.302 00.0460.004 0.050.790.06 0.0040.0450 0.050 0.900 0.050 0.050.890.06 00.160.15 0.130.220.12 0.100.140 0.31 0.46 0.24 0.220.510.26

14. Re-Sampling 00.0470.003 0.0450.8080.047 0.0050.0450 0.05 0.9 0.05 0.90.05 w1 w2 w3 w4 w5 w6 w7 w8 … W n Re- sample

15. Elicitation and Analysis Specify an interval which contains the probability of occurrence with 90% certainty. A case of illness due to Bacillus cereus toxin was transmitted by ingestion of Pork: ≤ 100% ≤0% ≤ 16 experts participated in the elicitation.

16. Results “Seed Variables” Some probabilities are believed to be zero therefore that value was used as the true value and used as a seed variable. Additionally 50% Fit was done based on the 5%, 50% and 95% quantile of the equal weight distribution 5% and 95% Fit was done based on the 5% and 95% quantile of the equal weight distribution

17. Issues Data Recollection Finding the experts. Encouraging them to participate and actually answer. No opportunity to give them guidance Number of experts per pathogen ** Validation How to evaluate the quality of the estimates Results

18. QUESTIONS

19. Expert 27

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