Leveraging risk assessment for foodborne outbreak investigations: The Quantitative Risk Assessment-Epidemic Curve Prediction Model

Root cause analysis can be used in foodborne illness outbreak investigations to determine the underlying causes of an outbreak and to help identify actions that could be taken to prevent future outbreaks. We developed a new tool, the Quantitative Risk Assessment-Epidemic Curve Prediction Model (QRA-EC), to assist with these goals and applied it to a case study to investigate and illustrate the utility of leveraging quantitative risk assessment to provide unique insights for foodborne illness outbreak root cause analysis. We used a 2019 Salmonella outbreak linked to melons as a case study to demonstrate the utility of this model (Centers for Disease Control and Prevention [CDC], 2019). The model was used to evaluate the impact of various root cause hypotheses (representing different contamination sources and food safety system failures in the melon supply chain) on the predicted number and timeline of illnesses. The predicted number of illnesses varied by contamination source and was strongly impacted by the prevalence and level of Salmonella contamination on the surface/inside of whole melons and inside contamination niches on equipment surfaces. The timeline of illnesses was most strongly impacted by equipment sanitation efficacy for contamination niches. Evaluations of a wide range of scenarios representing various potential root causes enabled us to identify which hypotheses, were likely to result in an outbreak of similar size and illness timeline to the 2019 Salmonella melon outbreak. The QRA-EC framework can be adapted to accommodate any food–pathogen pairs to provide insights for foodborne outbreak investigations.     

从市场势力到有效市场势力--以中国化学药品制剂制造业为例

企业层面市场势力及其福利损失的准确估计是产业组织领域的基础性研究问题,厘清市场份额、市场势力及福利损失的相互关系有助于为反垄断政策的制定提供参考并帮助企业决策。本文定义"有效市场势力"为企业销售额所占市场份额和Lerner指数的乘积,并证实在给定的垄断竞争行业中有效市场势力与福利损失存在近似线性关系,因此从福利分析的角度,有效市场势力比市场势力更需要被重视。通过理论分析,本文给出了企业层面市场势力和福利损失的估计方法,修正了以产出价值量代替实物量进行生产函数估计时存在的偏误。通过实证分析,本文将相关方法应用于中国化学药品制剂制造业研究,发现1999~2015年中国上市化药企业平均市场势力为0.149,未表现出太强的垄断性;样本期间每家上市化药企业每年平均福利损失为0.76亿元,约占营业收入的7%;政府规制对化药企业市场势力和有效市场势力具有一定的影响,但近年来该影响趋于稳定,因此放弃直接的药品价格规制转而依靠药品价格谈判机制和反垄断规制不会对化学药品制剂市场产生剧烈影响。     

Quantitative risk assessment-epidemic curve prediction model for leafy green outbreak investigation

The objective of this study was to leverage quantitative risk assessment to investigate possible root cause(s) of foodborne illness outbreaks related to Shiga toxin-producing Escherichia coli O157:H7 (STEC O157) infections in leafy greens in the United States. To this end, we developed the FDA leafy green quantitative risk assessment epidemic curve prediction model (FDA-LG QRA-EC) that simulated the lettuce supply chain. The model was used to predict the number of reported illnesses and the epidemic curve associated with lettuce contaminated with STEC O157 for a wide range of scenarios representing various contamination conditions and facility processing/sanitation practices. Model predictions were generated for fresh-cut and whole lettuce, quantifying the differing impacts of facility processing and home preparation on predicted illnesses. Our model revealed that the timespan (i.e., number of days with at least one reported illness) and the peak (i.e., day with the most predicted number of reported illnesses) of the epidemic curve of a STEC O157-lettuce outbreak were not strongly influenced by facility processing/sanitation practices and were indications of contamination pattern among incoming lettuce batches received by the facility or distribution center. Through comparisons with observed number of illnesses from recent STEC O157-lettuce outbreaks, the model identified contamination conditions on incoming lettuce heads that could result in an outbreak of similar size, which can be used to narrow down potential root cause hypotheses.     

在认知中实现英语工具书的教学教育功能

正确使用各类英语参考工具是培养英语认知能力应具备的基本技能。然而目前，我国高校英语专业工具书教学较为薄 弱，无法全面激发工具书的潜能，实现其真正价值。英语工具书教学应以培养工具书基本认知和使用能力为任务，以实现深层 认知和理性认知为最终目标，遵循资料性和方法论并重，理论与实践相结合，教为不教、学为续学的原则，引导学生从感性认知 向理性认知升华，从被动认知向主动认知过渡，真正实现英语工具书的教学教育功能。