Circulating avian influenza viruses now infect a broader range of wild birds and exhibit higher transmission rates, according to new research. Johanna Harvey, an assistant professor of wildlife disease ecology at the University of Rhode Island, co-authored a paper detailing these findings. The study, published in *Wildlife Monographs*, examines data gaps in avian influenza host dynamics. This research aims to prioritize wildlife conservation and protect human health.
Harvey collaborated with Jennifer Mullinax at the University of Maryland on this analysis. They are investigating how risk factors relate to biological traits to understand their interactions. The increased spread of highly pathogenic avian influenza viruses (HPAIV) adds a new stressor to bird species. These species already face population declines from climate change, habitat loss, and other factors. This situation creates a conservation crisis for wild birds, especially waterbirds and raptors.
Prior to the early 2000s, HPAIV outbreaks in wild birds were uncommon. They were largely confined to domestic birds. After 2005, HPAIV transmission in wild birds increased globally, often linked to migratory flyways. The H5N1 virus was first identified in wild hosts in 2002. Its detection marked a turning point, highlighting the potential for global spread through seasonal migration.
The H5 virus arrived in North America in 2014, primarily affecting poultry and some wild birds. A highly pathogenic virus reappeared in the U.S. in 2021. This was the H5N1 lineage A/Goose/Guangdong/1/96 (Gs/GD), which originated in China in 1996. Descendants of this strain became more adapted to wild birds. The current global H5 virus is a descendant of the Gs/GD virus.
This current wave of transmission has resulted in nearly 10,000 occurrences in wild birds. It has impacted 255 avian species. The dominant circulating strain has an elevated ability to infect hosts. Its spread and persistence in the U.S. are closely linked to its expanding host range, host demographics, and birds' seasonal behaviors. Peaks in virus activity coincide with periods when young birds, with developing immune systems, enter the population.
Some wild bird species, including house sparrows, mallard ducks, and trumpeter swans, are particularly susceptible to viral infection. Canada geese and some swans may act as supermover or superspreader hosts. Gulls have contributed to rapid transoceanic spread of HPAIV H5. Wild ducks facilitate swift regional dispersal. The research provides direction for future studies to inform mitigation efforts and offers insights for policymakers and wildlife management authorities.
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