Strategic challenges in the global control of high pathogenicity avian influenza

H5Nx goose/Guangdong Eurasian lineage high pathogenicity avian influenza (HPAI) viruses have been the main strains detected globally since 2005 and have spread around the world causing a panzootic that has spanned six continents with continual threat to not only wild and captive birds and poultry, but also to wild, captive and domestic mammals and humans. Its ecology and epidemiology, especially the 2.3.4.4b clade, has changed with over 489 species of birds infected, spreading the virus over migratory routes, resulting in death of many birds, including endangered species, and serving as a source for transmission to poultry and mammals. Improving surveillance and sharing of HPAI virus sequences, metadata and viruses across veterinary, public health, wildlife and environment sectors is needed to elucidate the complex population dynamics of the infections, crucial to addressing this complex One Health issue. The development of appropriate mitigation strategies or changes in husbandry, production and selling practices can reduce the risk of introduction of the virus into farms, its amplification and viral evolution, and any spill-back to wild birds. The approaches to prevention and control of HPAI in countries where these 2.3.4.4b viruses remain entrenched in poultry or places at risk of virus introduction via wild bird populations involve measures to reduce the effects of the disease in poultry (including enhanced farm biosecurity, vaccination, zoning and compartmentalisation). Their uptake reflects the difficulties encountered in relying solely on biosecurity for disease prevention and stamping-out alone for virus control and elimination. The Terrestrial Animal Health Code allows use of vaccination of poultry under specific conditions and without negatively impacting HPAI-free status if appropriate surveillance is conducted, thus supporting safe trade in poultry and poultry products. Nevertheless, concerns regarding loss of valuable export markets still interfere with greater utilisation of vaccination.