Informing Optimal Environmental Influenza Interventions: How the Host, Agent, and Environment Alter Dominant Routes of Transmission

Influenza can be transmitted through respirable (small airborne particles), inspirable (intermediate size), direct-droplet-spray, and contact modes. How these modes are affected by features of the virus strain (infectivity, survivability, transferability, or shedding profiles), host population (behavior, susceptibility, or shedding profiles), and environment (host density, surface area to volume ratios, or host movement patterns) have only recently come under investigation. A discrete-event, continuous-time, stochastic transmission model was constructed to analyze the environmental processes through which a virus passes from one person to another via different transmission modes, and explore which factors increase or decrease different modes of transmission. With the exception of the inspiratory route, each route on its own can cause high transmission in isolation of other modes. Mode-specific transmission was highly sensitive to parameter values. For example, droplet and respirable transmission usually required high host density, while the contact route had no such requirement. Depending on the specific context, one or more modes may be sufficient to cause high transmission, while in other contexts no transmission may result. Because of this, when making intervention decisions that involve blocking environmental pathways, generic recommendations applied indiscriminately may be ineffective; instead intervention choice should be contextualized, depending on the specific features of people, virus strain, or venue in question.

流感可通过呼吸性（小型空气传播颗粒）、吸入性（中等粒径）、直接飞沫喷射以及接触四种传播途径实现传播。此前，关于病毒毒株特性（感染性、存活能力、传播能力或排毒模式）、宿主群体（行为、易感性或排毒模式）以及环境因素（宿主密度、表面积体积比或宿主移动模式）如何影响上述传播途径的研究，直至近年才逐步得到关注。本研究构建了离散事件连续时间随机传播模型，用以分析病毒经由不同传播途径在人际间转移的环境作用过程，并探究各类传播模式的增强或削弱因素。除吸入途径外，其余单一传播途径在脱离其他传播模式的独立场景下，即可引发高水平传播。特定传播模式的传播效率对模型参数取值极为敏感，例如飞沫传播与呼吸性传播通常需要较高的宿主密度，而接触传播则无此类要求。根据具体场景的不同，一种或多种传播模式足以引发高水平传播，而在另一些场景中则可能无任何传播发生。正因如此，在制定阻断环境传播路径的干预决策时，不加区分地采用通用建议往往难以达到预期效果；反之，干预措施的选择应结合具体场景，根据目标人群、病毒毒株或相关场所的特定特征进行定制化调整。