Global economic impacts of Highly Pathogenic Avian Influenza: A systematic review and impact framework.

Highly Pathogenic Avian Influenza (HPAI) has risen globally since the early 2000s, causing economic impacts on industries, government, ecosystems, and society. A systematic literature review (SLR) following PRISMA guidelines was conducted to document and quantify the economic and financial impacts of HPAI. Data on economic methods, impact parameters and control strategy assessments were extracted. Impact estimates were converted into 2024 values and expressed as impact per agricultural GDP, per capita and average annual income. A framework categorising impact types was developed and quality was assessed using an adapted Consolidation Health Economic Evaluation Reporting Standards (CHEERS) protocol. Eighty-five papers covering 27 countries and 14 methodological approaches were analysed. Financial losses ranged from $1.14 million in USA, New York (1925) to $3881.87 million in Nigeria (2014-2016), with the later representing 0.43% of agricultural GDP, or $4.14 per person or approximately 280,000 annual incomes. Control strategies evaluated include vaccination, regionalisation, pre-emptive culling, surveillance, trade restrictions and bird housing orders. The framework identifies 135 impact parameters affecting the poultry industry, government, public health, other businesses and environment. Across all sectors direct costs dominate the literature, while direct consequential costs, indirect consequential costs and non-financial impacts remain relatively underexplored. Substantial quality variability was found with critical gaps in data transparency, incomplete costs and lack of standardisation of methods. This framework provides a vital comprehensive structure for future economic assessments, facilitating cross-study comparisons, enabling cost-benefit analyses of control strategies, and supporting more informed policy and investment decisions.