Improved swift Quantitative Microbiological Risk Assessment (sQMRA) methodology

Abstract

We developed an improved simplified Quantitative Microbiological Risk Assessment (QMRA) model and tool with reduced data need, applicable to any pathogen - food product combination and in addition suitable for basic QMRA education. The swift QMRA (sQMRA2) – model follows pathogen numbers through part of the food chain, starting at the retail phase, and ends with the estimated number of human cases of illness. The accompanying tool was implemented in Excel/@Risk. Relative risk (compared to other pathogen-food product combinations) rather than absolute risk was considered the most useful model output. The model includes storage at home (categories: room/fridge/freezer), cross-contamination (yes/no) and heating (done/undercooked/raw) during preparation in the kitchen and a dose response relationship (Binomial/Beta-Binomial). The model also includes variability, e.g. of pathogen concentration and food product heating (time, temperature) in the kitchen. The general setup of the sQMRA2 tool consists of 14 consecutive (sets of) questions for values of parameters and per phase detailed intermediate model output broken down into categories. On a separate sheet, attribution of storage, cross-contamination and heating transmission routes in terms of exposure (probability of a contaminated portion, number of cfu) and number of human cases are presented. Further, intermediate exposures (number of contaminated portions, number of cfu) and final risks (number of human cases, DALYs, cost of illness), relative as well as absolute, are given.sQMRA2 is useful for quickly obtaining relative public health risk QMRA estimates of multiple pathogen - food combinations, which can be directly useful for risk management in terms of attribution or for the selection of high risk candidates for the application of extensive QMRA. It is also useful for educational purposes because of the insightful presentation of intermediate and final model output. As an example, sQMRA2 calculations were given for Campylobacter and Salmonella in chicken fillet, filet americain and table eggs.