Global situation on avian influenza

Authors: Swayne, David

Submitted to: World Veterinary Poultry Association
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2020
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: High pathogenicity avian influenza (HPAI) viruses emerge from the mutation of H5 and H7 low pathogenicity avian influenza viruses (LPAI) after circulation in terrestrial poultry for a few weeks to years. There have been 42 genetically distinct HPAI epizootics since 1959 with varied epidemiological features: 1) introduction of H5/H7 low pathogenicity avian influenza (LPAI) virus from wild bird reservoir and mutation within a single flock to HPAI virus followed by eradication; 2) introduction of LPAI virus from wild bird reservoir and mutation within a single flock to HPAI virus with secondary spread before eradication, and 3) introduction of A/goose/Guangdong/1/1996 (Gs/GD) lineage of HPAI virus from wild birds or secondary spread from poultry. Items 1) and 2) above have mostly been associated with sporadic outbreaks of H5 and H7 HPAI; most recently in France, United Kingdom, Germany, Italy, and USA. Initially moving from wild birds to poultry as LPAI viruses, followed by mutation to HPAI viruses and contained on initial HPAI affected farm [1) above] or with secondary spread to other farms [2) above). In 2016, the H7N9 LPAI virus mutated to HPAI after circulating in poultry for 4 years. Since 2014, large outbreaks of Gs/GD lineage HPAI have occurred in poultry in USA, Taiwan, South Korea and African, Middle Eastern and European Union countries. Historically, the majority of the Gs/GD HPAI cases have been H5N1 but assortment of the virus has produced H5N2, H5N3, H5N5, H5N6 and H5N8 HPAI viruses of the 2.3.4.4 clade. Since 2014, the 2.3.4.4 viruses have diverged into eight genetic subgroups: a-h. Clade 2.3.2.1 Gs/GD H5Nx HPAI virus continues to circulate in Asia and Africa, and H7N3 HPAI virus in Mexico.