Centre for Zoonoses and Environmental Microbiology, Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), P.O. Box 1, NL-3720 BA Bilthoven, The Netherlands; Faculty of Veterinary Medicine, Institute for Risk Assessment Sciences (IRAS), Utrecht University, P.O. Box 80.178, NL-3508 TD Utrecht, The Netherlands.
Int J Food Microbiol. 2013 Sep 16;166(3):419-25. doi: 10.1016/j.ijfoodmicro.2013.07.025. Epub 2013 Aug 3.
Multiple outbreaks of human norovirus (hNoV) have been associated with fresh produce, such as soft berries and lettuce. Even though food handlers are considered an important source for the introduction of hNoV into food chains, their contribution to public health risks associated with hNoV remains unknown. To assess to which extent food handlers contribute to the introduction and spread of hNoV in fresh produce chains quantitative virus transfer data are needed. We estimated transfer proportions of hNoV GI.4, GII.4, murine norovirus (MNV-1), a culturable surrogate of hNoV, and human adenovirus (hAdV-2), a human pathogen proposed as an indicator for human faecal pollution, between gloved fingertips and raspberries, strawberries, and lettuce, by quantitative RT-PCR and cell culture if applicable. Virus transfer proportions were corrected for virus-matrix specific recoveries, and variability and uncertainty of the parameters were estimated. Virus transfer from gloves to soft berries was generally lower as compared to lettuce, with mean transfer proportions ranging between 0.1 to 2.3% and 9 to 10% for infectious MNV-1 and hAdV-2, respectively. Transfer from produce to glove was mostly greater than transfer from glove to produce, adding to the likelihood of virus transfer due to cross contamination from contaminated produce via food handlers. HNoV GI.4 and hNoV GII.4 showed no significant difference between their mean transfer proportions. Using the estimated transfer proportions, we studied the impact of low and high transfer proportions on the public health risk, based on a scenario in which a food handler picked raspberries with contaminated fingertips. Given the made assumptions, we could show that for a pathogen as infectious as hNoV, low transfer proportions may pose a greater public health risk than high transfer proportions, due to a greater viral spread. We demonstrated the potential of food handlers in spreading hNoV in food chains, showing that prevention of virus contamination on food handlers' hands is crucial for food safety. Nevertheless, complete prevention of virus contamination on fresh produce cannot be achieved in reality, and reliable and effective intervention measures are consequently required. We estimated that, especially for low transfer proportions, a robust one log10-unit reduction of infectious hNoV on contaminated produce, and on food handlers' hands, could lower the public health risk substantially. Using the obtained data in quantitative risk assessment will aid in elucidating the contribution of food handlers in hNoV transmission.
已有多项研究表明，人类诺如病毒（hNoV）与多种生食农产品相关，如软浆果和生菜。尽管食品处理人员被认为是将 hNoV 引入食物链的重要来源，但他们对与 hNoV 相关的公共健康风险的贡献仍不清楚。为了评估食品处理人员在生食农产品链中引入和传播 hNoV 的程度，需要定量病毒转移数据。我们通过定量 RT-PCR 和细胞培养（如果适用），估算了 hNoV GI.4、GII.4、鼠诺如病毒（MNV-1）（hNoV 的可培养替代物）和人腺病毒（hAdV-2）（作为人类粪便污染指示物的人类病原体）从手套指尖到覆盆子、草莓和生菜的转移比例。我们根据病毒-基质特定的回收率对病毒转移比例进行了校正，并估计了参数的变异性和不确定性。与生菜相比，病毒从手套转移到软浆果的比例通常较低，传染性 MNV-1 和 hAdV-2 的平均转移比例分别为 0.1%至 2.3%和 9%至 10%。从农产品到手套的转移大多大于从手套到农产品的转移，这增加了由于食品处理人员经手污染的农产品发生交叉污染而导致病毒转移的可能性。hNoV GI.4 和 hNoV GII.4 的平均转移比例没有显著差异。根据食品处理人员用污染的指尖采摘覆盆子的情景，我们使用估计的转移比例研究了低转移比例和高转移比例对公共健康风险的影响。根据所做的假设，我们可以表明，对于像 hNoV 这样具有传染性的病原体，低转移比例可能比高转移比例造成更大的公共健康风险，因为病毒传播得更广。我们证明了食品处理人员在食物链中传播 hNoV 的潜力，表明防止病毒污染食品处理人员的手部对于食品安全至关重要。然而，在现实中，无法完全防止病毒污染新鲜农产品，因此需要可靠和有效的干预措施。我们估计，特别是对于低转移比例，对污染的农产品和食品处理人员的手部上的传染性 hNoV 进行强有力的 1 个对数单位减少，可以大大降低公共健康风险。在定量风险评估中使用获得的数据将有助于阐明食品处理人员在 hNoV 传播中的作用。
