Department of Civil and Urban Engineering, New York University Tandon School of Engineering, Brooklyn, NY, USA E-mail:
School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ, USA; The Biodesign Institute Center for Environmental Health Engineering, Arizona State University, Tempe, AZ, USA.
J Water Health. 2021 Dec;19(6):918-932. doi: 10.2166/wh.2021.068.
Human noroviruses are a leading cause of food- and water-borne disease, which has led to an interest in quantifying norovirus health risks using quantitative microbial risk assessment (QMRA). Given the limited availability of quantitative norovirus data to input to QMRA models, some studies have applied a conversion factor to estimate norovirus exposure based on measured fecal indicator bacteria (FIB) concentrations. We conducted a review of peer-reviewed publications to identify the concentrations of noroviruses and FIB in raw, secondary-treated, and disinfected wastewater. A meta-analysis was performed to determine the ratios of norovirus-FIB pairs in each wastewater matrix and the variables that significantly impact these ratios. Norovirus-to-FIB ratios were found to be significantly impacted by the norovirus genotype, month of sample collection, geographic location, and the extent of wastewater treatment. Additionally, we evaluated the impact of using a FIB-to-virus conversion factor in QMRA and found that the choice of conversion ratio has a great impact on estimated health risks. For example, the use of a conversion ratio previously used in the World Health Organization Guidelines for the Safe Use of Wastewater, Excreta and Greywater predicted health risks that were significantly lower than those estimated with measured norovirus concentrations used as inputs. This work emphasizes the gold standard of using measured pathogen concentrations directly as inputs to exposure assessment in QMRA. While not encouraged, if one must use a FIB-to-virus conversion ratio to estimate norovirus dose, the ratio should be chosen carefully based on the target microorganisms (i.e., strain, genotype, or class), prevalence of disease, and extent of wastewater treatment.
人类诺如病毒是食源性和水源性疾病的主要原因，这促使人们采用定量微生物风险评估（QMRA）来量化诺如病毒的健康风险。鉴于可用于 QMRA 模型的定量诺如病毒数据有限，一些研究应用了转换因子，根据测量的粪便指示菌（FIB）浓度来估计诺如病毒暴露量。我们对同行评议的出版物进行了综述，以确定未处理、二级处理和消毒废水中的诺如病毒和 FIB 浓度。进行了荟萃分析以确定每种废水基质中诺如病毒-FIB 对的比值以及显著影响这些比值的变量。发现诺如病毒-FIB 比值受诺如病毒基因型、采样月份、地理位置和废水处理程度的显著影响。此外，我们评估了在 QMRA 中使用 FIB-病毒转换因子的影响，发现转换比的选择对估计的健康风险有很大影响。例如，使用世界卫生组织《安全使用废水、粪便和灰水指南》中先前使用的转换比预测的健康风险明显低于使用输入的测量诺如病毒浓度估计的风险。这项工作强调了在 QMRA 中直接使用测量病原体浓度作为暴露评估输入的黄金标准。虽然不鼓励，但如果必须使用 FIB-病毒转换比来估计诺如病毒剂量，则应根据目标微生物（即菌株、基因型或类别）、疾病流行程度和废水处理程度谨慎选择该比值。
