Abstract Title
Recent reports of avian influenza in Europe
Abstract
In the period 2020 to 2023 Europe suffered the largest epizootic ever recorded with H5 high pathogenicity avian influenza virus. The epizootic started in late 2020 due to clade 2.3.4.4b viruses. Initially cases were predominantly due to H5N8 virus but by early 2021 H5N1re-emreged being reported in wild and domestic birds. By the autumn of 2021 the H5N1 virus had almost completely replaced H5N8 in domestic birds although numerous subtypes (H5N1, H5N2, H5N3, H5N4, H5N5, H5N8) were reported in an increasing range of wild birds. To the present time the majority of infections in poultry are due to H5N1 reflecting the high incidence of the virus in local wild bird populations. The number of cases in domestic or captive birds in each season was as follows 2019/20 (331), 2020/21 (1386), 2021/22 (2808), 2022/23 (1319) and 2023/2024 (360) resulting in the death or culling of millions of poultry across multiple production sectors. The H5 HPAI viruses readily reassort with LPAI strains cocirculating in wild birds leading to the detection of over 90 different genotypes. The increased numbers of infected wild birds led to greater environmental contamination and spread of virus to previously unaffected species including seabirds. In some of these populations during the review period mortality was substantial. The epidemiological consequence was spill over on scale for the first time to mammalian hosts especially scavenging species, although most infections were single host, some farmed captive mammals became infected. In contrast there were very few poultry cases with H7 viruses.
Co-Author(s)
Ian H Brown
Pirbright Institute, Woking, Surrey, UK GU24 0NF
Abstract Category
Notable outbreaks, field and molecular epidemiology, and surveillance in poultry