Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor.
Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, Georgia.
Clin Infect Dis. 2020 Jan 16;70(3):493-500. doi: 10.1093/cid/ciz220.
Large norovirus (NoV) outbreaks are explosive in nature and vary widely in final size and duration, suggesting that superspreading combined with heterogeneous contact may explain these dynamics. Modeling tools that can capture heterogeneity in infectiousness and contact are important for NoV outbreak prevention and control, yet they remain limited.
Data from a large NoV outbreak at a Dutch scout jamboree, which resulted in illness among 326 (of 4500 total) individuals from 7 separate camps, were used to examine the contributions of individual variation in infectiousness and clustered contact patterns to the transmission dynamics. A Bayesian hierarchical model of heterogeneous, clustered outbreak transmission was applied to represent (1) between-individual heterogeneity in infectiousness and (2) heterogeneous patterns of contact.
We found wide heterogeneity in infectiousness across individuals, suggestive of superspreading. Nearly 50% of individual infectiousness was concentrated in the individual's subcamp of residence, with the remainder distributed over other subcamps. This suggests a source-and-sink dynamic in which subcamps with greater average infectiousness fed cases to those with a lower transmission rate. Although the per capita transmission rate within camps was significantly greater than that between camps, the large pool of susceptible individuals across camps enabled similar numbers of secondary cases generated between versus within camps.
The consideration of clustered transmission and heterogeneous infectiousness is important for understanding NoV transmission dynamics. Models including these mechanisms may be useful for providing early warning and guiding outbreak response.
大型诺如病毒（NoV）爆发具有爆发性，最终规模和持续时间差异很大，这表明超级传播者加上异质接触可能解释了这些动态。能够捕捉传染性和接触异质性的建模工具对于 NoV 爆发的预防和控制非常重要，但它们仍然有限。
利用在荷兰童子军大露营中发生的大型 NoV 爆发的数据，该爆发导致来自 7 个不同营地的 4500 人中的 326 人（共 326 人）患病，用于检查个体传染性的个体变异和聚集接触模式对传播动力学的贡献。应用异质、聚集爆发传播的贝叶斯分层模型来表示（1）个体间传染性的异质性和（2）异质的接触模式。
我们发现个体间的传染性存在广泛的异质性，提示存在超级传播者。几乎 50%的个体传染性集中在个体居住的分营中，其余分布在其他分营中。这表明存在源汇动态，其中平均传染性更高的分营将病例输送给传染性较低的分营。尽管营地内的人均传播率明显高于营地间的传播率，但营地间大量的易感个体使得营地内和营地间产生的继发病例数量相似。
考虑聚集传播和异质传染性对于理解 NoV 传播动态非常重要。包括这些机制的模型可能有助于提供早期预警和指导爆发应对。
