Avian influenza virus in water: global subtype diversity and spatial distribution patterns

Abstract

The current COVID-19 pandemic highlights the need for zoonotic\ninfectious disease surveillance. Avian influenza virus (AIV) poses a\nsignificant threat to animal and public health due to its pandemic\npotential. Virus-contaminated water has been suggested as an important\nAIV spread mechanism among multiple species. Nevertheless, few studies\nhave characterized the global AIV subtype diversity and distribution in\nenvironmental water. Therefore, this study aims to provide an updated\ndescriptive and phylogenetic analysis of AIVs isolated in water samples\nfrom high risk-sites for influenza outbreaks (i.e., live bird markets,\npoultry farms, and wild bird habitats) on a global scale. A total of 234\nhemagglutinin (HA) gene sequences of 21 subtypes were reported from nine\ncountries between 2003 – 2020. Fourteen AIV subtypes were solely\nreported from Asian countries. Most of the viral sequences were obtained\nin China and Bangladesh with 47.44% and 23.93%, respectively.\nLikewise, the greatest global AIV subtype diversity was observed in\nChina with twelve subtypes. Live bird markets represented the main\nsampling site for AIV detection in water samples (64.10%), mostly from\npoultry cage water. Nevertheless, the highest subtype diversity was\nobserved in water samples from wild bird habitats, especially from the\nIzumi plain and the Dongting Lake located in Japan and China,\nrespectively. Water from drinking poultry troughs evidenced the greatest\nsubtype diversity in live bird markets, meanwhile, environmental water\nused by ducks had the highest number of different subtypes in poultry\nfarms. The maximum-likelihood phylogenetic tree showed that some HA\nsequences were closely related among different poultry/wild bird-related\nenvironments from different geographic origins. Therefore, the results\nsuggest that even though the availability of HA gene sequences in\npublic-access databases varies greatly among countries, environmental\nAIV surveillance represents a useful tool to elucidate potential viral\ndiversity in wild and domestic bird populations.