When does a supershedder become a superspreader?: The impact of individual-level heterogeneities on population-level transmission and spread

超级传播者何时成为超级传播者？：个体水平异质性对群体水平传播和传播的影响

• 批准号: NE/X01424X/1
• 负责人: Amy Pedersen
• 金额: $ 103.47万
• 依托单位: University of Edinburgh
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2024
• 资助国家: 英国
• 起止时间: 2024 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FX01424X%2F1
• 关键词: When; does; supershedder; become; superspreader

Individuals vary greatly in both their susceptibility to infection and their likelihood of transmitting infections to others. Evidence from various disease outbreaks suggests that typically a minority of individuals (~20%) cause the majority of new cases (~80%) - these are the so-called "superspreaders". However, it is not clear what characteristics make someone a superspreader. As we are only too aware from the COVID-19 pandemic, an individual's infection risk depends on how close and for how long they spend near infected individuals, such that some infected individuals may contact a disproportionately high number of susceptible individuals, acting as 'supercontactors'. Hence, supercontactors may indeed be superspreaders and drive transmission for many infectious diseases. However, it is also possible that some individuals release many more infectious stages than others, acting as 'supershedders', which can also lead to disproportionately greater transmission potential. To complicate matters, these two processes, supershedding and supercontacting, can interact together - either exacerbating transmission (generally, if supershedders also tend to be supercontactors) or diminishing transmission (if supershedders tend to have few contacts, and vice versa). These processes, whether driven by individuals having large numbers of contacts or being highly infectious, then scale up to determine how fast the parasite spreads through the host population, and the spatial distribution of infection 'hotspots'. As such, understanding the individual characteristics that determine supershedders and supercontactors, and how they are coupled to give rise to superspreaders, are crucial to predicting disease spread and for devising effective control measures.So far, research on what host characteristics make a superspreader has focussed almost exclusively on pathogenic viral or bacterial outbreaks in humans. While clearly essential from a public health perspective, this narrow focus on certain human pathogens limits our ability to explicitly test the mechanisms underlying superspreading. Furthermore, it is far from clear how ideas of supercontacting and supershedding apply to the vast range of parasites with very different transmission modes and biologies from the pathogens that cause epidemics (or pandemics) in humans. In particular, parasitic worms (helminths) are a ubiquitous and integral component of all natural ecosystems, playing a vital role in structuring ecological communities and having significant health and economic consequences for wildlife, humans and domestic animals. These helminths typically infect new hosts through long-lived infective stages that reside in the environment, thereby blurring the definition of 'contacts', and making it virtually impossible to determine the number of new infections arising from each initially infected individual. Hence, established concepts relating supershedding, supercontacting, and superspreading do not apply directly to this important groups of parasites.Here we will move this field forward through a comprehensive study that uses novel population-level field experiments in a highly tractable yet natural host-parasite system, wood mice and their parasitic worms, in which we can specifically reduce infections in either supershedding or supercontacting individuals. We will pair these field experiments with new theory and robust analytical methods to develop an in-depth understanding of how between-individual variation in infectiousness, movement patterns, and parasite transmission mode interact to drive parasite spread in natural communities.

每个人对感染的易感性以及将感染传播给他人的可能性都有很大差异。来自各种疾病爆发的证据表明，通常少数人（约 20%）导致了大多数新病例（约 80%）——这些就是所谓的“超级传播者”。然而，尚不清楚哪些特征使某人成为超级传播者。我们对 COVID-19 大流行非常了解，一个人的感染风险取决于他们与感染者的距离和时间，因此一些感染者可能会接触到不成比例的大量易感者，充当“超级接触者” '。因此，超级接触者确实可能是超级传播者并推动许多传染病的传播。然而，也有可能某些人比其他人释放更多的传染性阶段，充当“超级传播者”，这也可能导致不成比例的更大传播潜力。让事情变得复杂的是，超级脱落和超级接触这两个过程可以相互作用——要么加剧传播（通常，如果超级脱落者也往往是超级接触者），要么减少传播（如果超级脱落者往往接触很少，反之亦然）。这些过程，无论是由具有大量接触的个体还是具有高度传染性的个体驱动，然后扩大规模以确定寄生虫在宿主群体中传播的速度以及感染“热点”的空间分布。因此，了解决定超级传播者和超级接触者的个体特征，以及它们如何耦合产生超级传播者，对于预测疾病传播和制定有效的控制措施至关重要。到目前为止，关于超级传播者的宿主特征的研究主要集中在哪些方面几乎专门针对人类致病病毒或细菌的爆发。虽然从公共卫生的角度来看显然很重要，但这种对某些人类病原体的狭隘关注限制了我们明确测试超级传播机制的能力。此外，目前还不清楚超级接触和超级脱落的想法如何适用于与引起人类流行病（或大流行）的病原体截然不同的传播模式和生物学特性的大量寄生虫。特别是，寄生虫是所有自然生态系统中普遍存在的不可或缺的组成部分，在构建生态群落方面发挥着至关重要的作用，并对野生动物、人类和家畜产生重大的健康和经济影响。这些蠕虫通常通过环境中的长期感染阶段感染新宿主，从而模糊了“接触者”的定义，并且几乎不可能确定每个最初感染个体产生的新感染数量。因此，有关超级脱落、超级接触和超级传播的既定概念并不直接适用于这一重要的寄生虫群体。在这里，我们将通过一项综合研究推动这一领域向前发展，该研究在高度易处理但天然的宿主寄生虫中使用新颖的种群水平现场实验系统、木鼠及其寄生蠕虫，我们可以在其中专门减少超级脱落或超级接触个体的感染。我们将这些现场实验与新的理论和强大的分析方法结合起来，深入了解个体之间的传染性、运动模式和寄生虫传播模式的变异如何相互作用，从而推动寄生虫在自然群落中的传播。