Table_1_Risk factors for avian influenza in Danish poultry and wild birds during the epidemic from June 2020 to May 2021.docx

Exploring the risk factors of avian influenza (AI) occurrence helps us to monitor and control the disease. Since late 2020, the number of avian influenza outbreaks in domestic and wild birds has increased in most European countries, including Denmark. This study was conducted to identify potential risk factors for wild birds and poultry during the epidemic in 2020/2021 in Denmark. Using Danish AI surveillance data of actively surveyed poultry and passively surveyed wild birds from June 2020 to May 2021, we calculated geographical attributes for bird locations and assessed the potential risk factors of AI detections using logistic regression analyses. 4% of actively surveyed poultry and 39% of passively surveyed wild birds were detected with AI circulating or ongoing at the time. Of these, 10 and 99% tested positive for the H5/H7 AI subtypes, respectively. Our analyses did not find any statistically significant risk factors for actively surveyed poultry within the dataset. For passively surveyed wild birds, bird species belonging to the Anseriformes order had a higher risk of being AI virus positive than five other taxonomic bird orders, and Galliformes were of higher risk than two other taxonomic bird orders. Besides, every 1 km increase in the distance to wetlands was associated with a 5.18% decrease in the risk of being AI positive (OR (odds ratio) 0.95, 95% CI 0.91, 0.99), when all other variables were kept constant. Overall, bird orders and distance to wetlands were associated with the occurrence of AI. The findings may provide targets for surveillance strategies using limited resources and assist in risk-based surveillance during epidemics.

探索禽流感（Avian Influenza, AI）暴发的危险因素，有助于该疫病的监测与防控。自2020年末以来，包括丹麦在内的多数欧洲国家在家禽与野生鸟类中暴发的禽流感疫情数量均呈上升趋势。本研究旨在明确2020/2021年丹麦禽流感疫情期间，野生鸟类与家禽感染禽流感的潜在危险因素。本研究利用2020年6月至2021年5月期间丹麦的禽流感监测数据——包括主动监测的家禽与被动监测的野生鸟类数据，计算了鸟类栖息地点的地理属性，并通过逻辑回归分析评估了禽流感检出的潜在危险因素。在此期间，主动监测的家禽中4%检出处于传播期或暴发期的禽流感病毒，被动监测的野生鸟类中这一比例达39%。其中，分别有10%的阳性家禽样本与99%的阳性野生鸟类样本为H5/H7亚型禽流感病毒检测阳性。本研究的分析结果显示，本次数据集内的主动监测家禽样本未发现具有统计学意义的危险因素。针对被动监测的野生鸟类而言，属于雁形目（Anseriformes）的鸟类相较于其余5个鸟类分类目，感染禽流感病毒的风险更高；而鸡形目（Galliformes）的风险则高于另外2个鸟类分类目。此外，在控制其余所有变量的前提下，距湿地的距离每增加1公里，禽流感病毒检测阳性的风险便会降低5.18%（优势比（odds ratio, OR）为0.95，95%置信区间为0.91~0.99）。总体而言，鸟类分类目与距湿地的距离均与禽流感的暴发存在关联。本研究结果可为有限资源下的监测策略制定提供方向，并有助于疫情期间开展基于风险的监测工作。