Usutu virus is an emerging zoonotic flavivirus causing high avian mortality rates and occasional severe neurological disorders in humans. Several virus strains are co-circulating and the differences in their characteristics and avian pathogenesis levels are still unknown. In this study, we use within–host mathematical models to characterize the mechanisms responsible for virus expansion and clearance in juvenile chickens challenged with four Usutu virus strains. We find heterogeneity between the virus strains, with the time between cell infection and viral production varying between 16 h and 23 h, the infected cell lifespan varying between 48 min and 9.5 h, and the basic reproductive number $R_0$ varying between 12.05 and 19.49. The strains with high basic reproductive number have short infected cell lifespan, indicative of immune responses. The virus strains with low basic reproductive number have lower viral peaks and longer lasting viremia, due to lower infection rates and high infected cell lifespan. We discuss how the host and virus heterogeneities may differently impact the public health threat presented by these virus strains.

乌苏图病毒是一种新兴的人畜共患病黄病毒，可导致高禽类死亡率和人类偶发的严重神经系统疾病。几种病毒株同时传播，它们的特征和禽类发病水平的差异仍然未知。在这项研究中，我们使用宿主内数学模型来描述在受到四种乌苏图病毒株攻击的幼鸡中负责病毒扩增和清除的机制。我们发现病毒株之间存在异质性，细胞感染和病毒产生之间的时间在 16 小时和 23 小时之间变化，被感染的细胞寿命在 48 分钟和 9.5 小时之间变化，基本繁殖数$R_0$在 12.05 和 19.49 之间变化。基本繁殖数高的菌株感染细胞寿命短，表明有免疫反应。由于较低的感染率和较高的感染细胞寿命，具有较低基本繁殖数的病毒株具有较低的病毒峰值和较长持续的病毒血症。我们讨论了宿主和病毒的异质性如何不同地影响这些病毒株所带来的公共卫生威胁。