Circulation of avian influenza viruses in migratory birds in Europe and in Africa: a systematic review.

Avian influenza virus (AIV) is an increasing driver of the emergence and re-emergence of outbreaks in both animal and human populations worldwide. Its circulation is influenced by migratory birds, human activities, and climate change. Europe and Africa encompass several major migratory flyways that are undergoing substantial environmental and ecological changes. In this systematic review, conducted in accordance with PRISMA guidelines, we analysed published studies reporting AIV detection in migratory birds across Europe and Africa. A total of 72 publications (2005-2025) were included, comprising 53 from Europe and 19 from Africa. Overall, 10,960 migratory birds representing 166 species, 32 families, and 17 orders were reported across the three principal flyways connecting Europe and Africa: the Atlantic, Mediterranean, and Bosphorus flyways. Publication trends aligned with major HxNy outbreak over the past decade. Both low- and high-pathogenic avian influenza viruses (LPAIV and HPAIV) were detected, with a predominance of LPAIV (86% vs. 14% HPAIV). LPAIV were reported consistently throughout the study period, whereas HPAIV detections were largely confined to periods following the 2005 H5N1 outbreak and the outbreak waves after 2020. H5N1 accounted for 11% of AIV detections and was reported in 17 European countries and 4 African countries with a dominance of the clade 2.3.4.4b since 2020. Overall, this review underscores the contribution of diverse avian orders to AIV circulation - particularly in the emergence and re-emergence of H5N1 - and highlights the central role of the Mediterranean flyway in the interconnection of the 3 flyways in AIV surveillance between Europe and Africa.