Avian Influenza: Landscape Changes in East Asia Are Facilitating the Emergence of New Viruses

A study shows that the transformation of wetlands and agricultural areas accelerates the diversification of avian influenza viruses. Rapid landscape changes along the East Asia–Australasia (EAAF) flyway significantly increase the risk of new avian influenza subtypes emerging. This is the conclusion of a study published in mid-August in the journal *Proceedings of the National Academy of Sciences* (PNAS).  

A Migratory Corridor Under Ecological Pressure

The East Asia–Australasia flyway is one of the most important in the world. Every year, millions of waterbirds travel along it between Siberia, Mongolia, and their wintering grounds in China and Southeast Asia. These birds play a central role in the dynamics of avian influenza viruses. However, between 2000 and 2015, this region underwent profound environmental changes. The gradual disappearance of wetlands in eastern China, Japan, and Korea has reduced the available space for migratory birds. At the same time, the area of rice paddies has increased in northern China, attracting more migratory birds. The local increase in flooded areas in Russia and northeastern China—linked to the abandonment of farmland and climate change—has also altered the spatial distribution of species. These changes are leading to a redistribution of bird populations. Some species are now concentrated in restricted habitats, where high density facilitates viral transmission. Others are colonizing agricultural areas shared with domestic poultry, which increases the risk of contact and, consequently, of cross-transmission.  

The Key Role of Genetic Reassortment

One of the most concerning mechanisms in the evolution of influenza viruses is genetic reassortment. When a host—whether a wild bird or domestic poultry—is simultaneously infected by two different strains, these viruses can exchange gene segments and create a new subtype. This process does not automatically guarantee the emergence of a highly pathogenic strain, but it significantly increases viral diversity and sets the stage for the emergence of more dangerous variants. The study emphasizes that domestic poultry act as a veritable “incubator” for viruses. Indeed, while wild birds carry many low pathogenic avian influenza (LPAI) viruses, their transmission to poultry farms promotes co-infections and increases opportunities for reassortment. In a context where shared agricultural areas (particularly rice paddies) are increasing, the conditions are ripe for accelerating the diversification of strains.  

A Novel Modeling Approach to Measure the Impact of Landscapes

To quantify these risks, the researchers developed an individual-based model (IBM). This model draws on a variety of empirical data: satellite tracking of 79 white-fronted geese (Anser albifrons ) fitted with GPS collars between 2014 and 2016, field data from the eBird platform, remote sensing to map wetlands, rice paddies, and water bodies, as well as information on domestic poultry density. This model made it possible to simulate migrations and estimate the dynamics of transmission between wild birds and poultry. By comparing the years 2000 and 2015, the researchers assessed how changes in the landscape influenced viral circulation. To take their analysis further, they used advanced statistical methods, such as piecewise structural equation modeling (piecewiseSEM), to identify the environmental variables with the greatest impact on bird distribution and the incidence of reassortment.  

Alarming results: a sixteen-fold increase in risk

The model’s results are revealing. Between 2000 and 2015, the rate of viral reassortment increased by 1,593 percent—a sixteen-fold increase. The risk areas, initially concentrated in a few hotspots, have expanded to encompass southeastern China, the Yellow River basin, and northeastern China. New rice-growing areas in the north attract large populations of migratory birds, automatically increasing the likelihood of contact with poultry. These findings are consistent with historical observations. No major reassortment events had been reported prior to 1995, but between 1996 and 2015, their frequency rose sharply in East Asia, in parallel with changes in the landscape.  

Direct Implications for Agriculture and Public Health

Since its emergence in 1996, the highly pathogenic H5 virus has continued to diversify. Subtypes such as H5N8 and H5N1 clade 2.3.4.4b have crossed new species barriers, affecting wild birds, poultry, marine mammals, and dairy cattle. These crossings demonstrate that the evolution of influenza viruses is not independent of human activities: on the contrary, it is amplified by agriculture, urbanization, and landscape management. For poultry farmers, the proximity of poultry farms to wetlands and rice-growing areas poses a major risk. For health authorities, the prospect of new strains transmissible to humans necessitates strengthening virological surveillance in risk areas. For ecologists, wetland management is no longer just a biodiversity issue, but also a component of global health security.  

Toward an Integrated “One Health” Approach

The authors emphasize the need to adopt a truly interdisciplinary approach, in the spirit of the “One Health” concept. Understanding and preventing viral outbreaks requires combining the ecology of migration, the evolutionary biology of viruses, computational modeling, and agricultural policies. Virus dynamics depend not only on random mutations but also on land-use decisions and climate change. As one of the authors points out, “Changes in the landscape are not merely visual transformations; they are redrawing the global map of infectious disease risks.”  

Climate, Agriculture, and Viruses: A High-Risk Future

The study clearly demonstrates that changes in agricultural and natural landscapes play a central role in the evolution of avian influenza viruses. As climate change, agricultural intensification, and biodiversity loss accelerate, the risk of new strains of concern emerging is higher than ever. The Yangtze River basin, the Yellow River, and China’s vast rice-growing plains are not only strategically important areas for agriculture; they now appear to be potential hotspots for the next major viral mutation.