Rapid Evolution of Bird Flu Enhances Infection and Spread Among Hosts

Recent studies reveal that the bird flu (H5N1) virus continues to evolve at an accelerated pace, increasing its ability to infect a broader range of hosts and spread more effectively across regions. Since its detection in Canada in 2021, where it led to the culling of over 180 million domestic birds in North America, the virus has shown significant genetic changes. New evidence published in Science Advances indicates that H5N1 is mixing with low-pathogenic avian influenza viruses (LPAIVs), broadening its host susceptibility and geographical distribution.

Researchers analyzed nearly 3,000 viral genomes collected from both wild and domestic birds between 2021 and 2024 across Canada. Combining this data with previous analyses, they mapped the virus's genetic evolution and migration patterns throughout North and South America, largely facilitated by migratory birds. Their findings highlight increased viral fitness — the virus’s capacity to replicate, adapt, and transmit — driven by frequent reassortments. These reassortments occur when two or more viruses infect a single host cell and exchange genetic material, resulting in new variants with enhanced abilities to infect more hosts and spread across larger areas.

The study observed that successive reassortments have led to the emergence of dominant, more competitive genotypes. Particularly concerning is the role of migratory routes, especially the Prairie Pothole Region in the Great Plains, which serves as a hotspot for viral mixing among waterfowl such as ducks and geese. The synchronization of migratory periods with spikes in viral detection confirms that wild birds are main vectors in spreading newer, more virulent strains, making containment more challenging compared to past outbreaks that were mainly limited to domestic poultry.

Additionally, there is evidence of the virus crossing into mammalian hosts, including some spread back to bird populations, heightening concerns over potential zoonotic transmission. The high mortality rate in poultry, combined with the increased spread to other animals and humans, underscores the importance of ongoing surveillance and research. Improving understanding of the virus’s genetic evolution and migration dynamics can help develop better strategies for controlling outbreaks and preventing future pandemics.

In summary, the rapid genetic changes and expanding transmission pathways of the bird flu virus suggest an urgent need for heightened biosecurity measures and continuous monitoring to mitigate the risk of widespread infection in both avian and mammalian populations.

Source: https://medicalxpress.com/news/2025-07-bird-flu-evolve-rapidly-infecting.html