Seasonality in the migration and establishment of H3N2 Influenza lineages with epidemic growth and decline

Background: Influenza A/H3N2 has been circulating in humans since 1968, causing considerable morbidity and mortality. Although H3N2 incidence is highly seasonal, how such seasonality contributes to global phylogeographic migration dynamics has not yet been established. In this study, we incorporate time-varying migration rates in a Bayesian MCMC framework. We focus on migration within China and between China and North-America as case studies, then expand the analysis to global communities. Results: Incorporating seasonally varying migration rates improves the modeling of migration in our case studies, and of global influenza population dynamics. In our global model, windows of increased immigration (in migration) map to the seasonal timing of epidemic spread, while windows of increased emigration (out migration) map to epidemic decline. Seasonal patterns also correlate with the probability that local lineages go extinct and fail to contribute to long term viral evolution, as measured th...

背景：甲型H3N2流感病毒自1968年起即在人群中持续循环传播，引发了大量的发病与死亡病例。尽管H3N2的感染呈现显著的季节性特征，但其季节性如何作用于全球流感的系统地理迁徙动态，目前仍未明确。本研究在贝叶斯马尔可夫链蒙特卡洛（Bayesian Markov Chain Monte Carlo，MCMC）框架中纳入时变迁徙速率参数，以中国国内以及中国与北美之间的流感迁徙为案例开展研究，随后将分析范围拓展至全球传播单元。结果：纳入季节性变化的迁徙速率后，本研究案例中的迁徙建模效果以及全球流感种群动态模型均得到优化。在全球模型中，病毒迁入量增加的时间窗口与疫情传播的季节性节点相匹配，而病毒迁出量增加的时间窗口则对应疫情消退阶段。季节性模式还与本地病毒谱系灭绝、无法为病毒长期演化做出贡献的概率相关，以……衡量。