Data from: Demographic and spatiotemporal patterns of avian influenza infection at the continental scale, and in relation to annual life cycle of a migratory host

Since the spread of highly pathogenic avian influenza (HPAI) H5N1 in the eastern hemisphere, numerous surveillance programs and studies have been undertaken to detect the occurrence, distribution, or spread of avian influenza viruses (AIV) in wild bird populations worldwide. To identify demographic determinants and spatiotemporal patterns of AIV infection in long distance migratory waterfowl in North America, we fitted generalized linear models with binominal distribution to analyze results from 13,574 blue-winged teal (Anas discors, BWTE) sampled in 2007 to 2010 year round during AIV surveillance programs in Canada and the United States. Our analyses revealed that during late summer staging (July-August) and fall migration (September-October), hatch year (HY) birds were more likely to be infected than after hatch year (AHY) birds, however there was no difference between age categories for the remainder of the year (winter, spring migration, and breeding period), likely due to maturing immune systems and newly acquired immunity of HY birds. Probability of infection increased non-linearly with latitude, and was highest in late summer prior to fall migration when densities of birds and the proportion of susceptible HY birds in the population are highest. Birds in the Central and Mississippi flyways were more likely to be infected compared to those in the Atlantic flyway. Seasonal cycles and spatial variation of AIV infection were largely driven by the dynamics of AIV infection in HY birds, which had more prominent cycles and spatial variation in infection compared to AHY birds. Our results demonstrate demographic as well as seasonal, latitudinal and flyway trends across Canada and the US, while illustrating the importance of migratory host life cycle and age in driving cyclical patterns of prevalence.

自东半球高致病性禽流感（Highly Pathogenic Avian Influenza, HPAI）H5N1传播以来，全球范围内已开展大量监测计划与研究，用以检测野生鸟类种群中禽流感病毒（Avian Influenza Virus, AIV）的发生、分布及传播情况。为明确北美长途迁徙水禽感染AIV的人口统计学决定因素与时空分布模式，本研究采用拟合二项分布（Binomial Distribution）的广义线性模型（Generalized Linear Model），对2007至2010年全年在加拿大与美国开展的AIV监测项目中采集的13574只蓝翅鸭（Blue-winged Teal, Anas discors, BWTE）样本进行分析。研究结果表明：在夏末集结期（7月至8月）与秋季迁徙期（9月至10月），当年雏鸟（Hatch Year, HY）的感染概率显著高于越年个体（After Hatch Year, AHY）；但在一年其余时段（冬季、春季迁徙期及繁殖期），不同年龄组的感染概率并无显著差异，这一现象可能与当年雏鸟逐渐成熟的免疫系统及新获得的免疫力有关。感染概率随纬度呈非线性增长，并在秋季迁徙前的夏末达到峰值，此时鸟类种群密度与种群中易感当年雏鸟的占比均处于最高水平。中央迁徙通道与密西西比迁徙通道内的个体感染AIV的概率显著高于大西洋迁徙通道内的个体。AIV感染的季节周期与空间变异主要由当年雏鸟的感染动态所驱动，与越年个体相比，当年雏鸟的感染周期与空间变异更为显著。本研究结果揭示了加拿大与美国境内AIV感染的人口统计学、季节、纬度及迁徙通道层面的趋势，同时阐明了迁徙宿主的生活史与年龄特征在驱动感染流行率周期性模式中的重要作用。