Foodborne illness outbreaks have been increasingly linked to the consumption of fresh and frozen berries that were contaminated with pathogenic viruses, such as human norovirus (NoV). Contamination of berries is assumed to take place at harvest by the use of contaminated water for pesticide dilution, irrigation water source or by shedding berry pickers in the field. A quantitative microbial risk assessment simulation model was built to replicate the largest known NoV outbreak which sickened about 11,000 people over a 3-week period. The outbreak occurred in Germany in 2012 when contaminated frozen strawberries were served at nearly 400 schools and daycare centers. The risk model explicitly assumed that all contamination would arise from NoV contamination of surface water used for pesticide dilution. Input data was collected from the published literature, observational studies and assumptions. The model starts with contamination of the berries in the field, and proceeds through transportation to processing facility, washing, sanitizing, freezing, frozen transport to cargo ship, transport view of cargo ship, transport to distribution center, frozen storage at the distribution center, transport to the catering facility, food service preparation and consumption, dose response, and predicted illnesses. A total of 21 scenarios were chosen to evaluate the impact of model parameters on the number of illness associated with NoV contamination of berries. Scenarios evaluated include the initial level of NoV in surface water, the effect of seasonality on the prevalence of NoV in surface water, the strength of the pesticide used, the volume of water used to dilute the pesticide, temperature during transportation to processing facility, washing and sanitizing conditions at processing facility and preparation (heat-treatment) of berries prior to consumption. Scenarios were compared via the Factor Sensitivity technique where the logarithm of the ratio of mean illnesses was used to compare different assumptions. The input that had the greatest effect on increasing in the number of illnesses was a high NoV concentration in the water (8 log Genome Copies/L) when compared to the baseline scenario with resulting mean illnesses of 7964 illnesses and ∼2 illnesses, respectively. This assumption about the concentration of virus in the pesticide makeup water was the only variable capable of producing an outbreak similar to that observed in Germany in 2012. Heat-treatment of the berries, use of a pesticide with strong antiviral effect, and assumption about the virus concentration in the pesticide make-up water had the largest impact on decreasing illnesses.

食源性疾病暴发与食用被人诺如病毒（NoV）等病原性病毒污染的新鲜和冷冻浆果的联系日益紧密。假定在收获时通过使用受污染的水稀释农药，灌溉水源或在田间采摘浆果来污染浆果。建立了定量的微生物风险评估模拟模型，以复制已知的最大的NoV暴发，该暴发在3周内使约11,000人患病。暴发发生在2012年的德国，当时在近400所学校和日托中心提供了受污染的冷冻草莓。该风险模型明确假设所有污染将来自农药稀释所用地表水的NoV污染。输入数据来自已发表的文献，观察研究和假设。该模型从野外的浆果污染开始，然后进行运输到加工设施，清洗，消毒，冷冻，冷冻运输到货船，运输货船的视图，运输到配送中心，配送中心的冷冻仓库，运输到餐饮设施，准备食物和消费，剂量反应以及预期的疾病。总共选择了21种方案来评估模型参数对浆果NoV污染相关疾病数量的影响。评估的方案包括地表水中NoV的初始水平，季节性因素对地表水中NoV流行的影响，所使用农药的强度，用于稀释农药的水量，运输到加工厂的温度，加工厂的洗涤和消毒条件以及食用前浆果的制备（热处理）。通过因素敏感度技术比较了情景，其中平均疾病比率的对数用于比较不同的假设。与基线情景相比，对疾病数量增加影响最大的输入是水中的高NoV浓度（8 log基因组拷贝数/升），分别导致平均疾病7964例和2例。关于农药补充水中病毒浓度的这一假设是唯一能够导致爆发的变量，与2012年德国观察到的类似。