Researchers Warn That H5N1 Virus is Recombining with other Low Pathogenic Bird Flu Viruses Such as H11N2
Nikhil Prasad Fact checked by:Thailand Medical News Team Jun 28, 2026 1 hour, 21 minutes ago
Thailand Medical News:
New Discovery Raises Fresh Questions About Bird Flu Evolution
Scientists have uncovered important evidence showing that the highly pathogenic H5N1 avian influenza virus is sharing genetic material with low pathogenic bird flu viruses circulating in wild migratory birds. Although the newly identified H11N2 virus is itself considered low pathogenic, researchers found that one of its key genetic components is closely related to the H5N1 lineage that has spread across the Americas in recent years.
Scientists discovered a low pathogenic H11N2 bird flu virus carrying a key H5N1-related gene, highlighting ongoing
influenza evolution in migratory birds.
The research was carried out by scientists from the University of São Paulo, St. Jude Children's Research Hospital, CNPEM–Brazilian Center for Research in Energy and Materials, Universidade do Vale do Rio dos Sinos (UNISINOS), Federal University of Rio Grande (FURG), Federal University of Rio Grande do Sul (UFRGS), Hospital Israelita Albert Einstein, University of Campinas (UNICAMP), and the Institut Pasteur of São Paulo.
A Rare Virus Found in a Migratory Shorebird
The researchers detected the H11N2 virus in a white-rumped sandpiper captured at Lagoa do Peixe National Park in southern Brazil during surveillance of migratory birds. Out of 40 birds tested, only one bird was positive for avian influenza.
Using whole-genome sequencing, the team analyzed all eight genetic segments of the virus. Seven of those segments closely matched H11N2 viruses previously found in migratory shorebirds from Delaware Bay in the United States. However, the eighth segment, known as PB1, told a very different story.
The PB1 gene showed about 99 percent similarity to the PB1 lineage associated with the highly pathogenic H5N1 clade 2.3.4.4b viruses that have caused devastating outbreaks in birds and infected mammals across North and South America.
Evidence of Viral Recombination
Influenza viruses possess segmented genomes, allowing them to exchange entire gene segments whenever two different influenza viruses infect the same host. This process, known as reassortment, creates new viral combinations that may acquire different biological characteristics.
This
Thailand Medical News report highlights that the Brazilian H11N2 virus represents such a reassortant virus. While seven of its genes belonged to a typical North American low pathogenic H11N2 virus, the PB1 segment originated from a genetic lineage linked to H5N1.
Detailed phylogenetic analysis, nucleotide comparisons, and molecular clock studies showed that the PB1 lineage shared by both viruses likely originated from North American low pathogenic avian influenza viruses around 2020, well before H5N1 became established in South America. This indicates that the genetic building blocks of today's H5N1 viruses were already circulating among wild birds years e
arlier.
Migratory Birds Continue to Spread Viral Diversity
The white-rumped sandpiper migrates thousands of kilometers annually between the Canadian Arctic and South America. Such long-distance migration enables influenza viruses from different regions to mix when birds gather at shared stopover sites.
Researchers found that the H11N2 virus carried a predominantly North American genetic background rather than one previously established in South America. The findings demonstrate how migratory birds continually introduce new influenza viruses and genetic segments across continents.
Although the virus discovered in Brazil was not highly pathogenic, scientists emphasized that these ongoing exchanges of genetic material create opportunities for future viral evolution that could influence disease spread in wild birds and possibly poultry.
Why the Findings Matter
Importantly, the study does not suggest that the Brazilian H11N2 virus directly evolved from the current H5N1 viruses circulating in South America. Instead, both viruses inherited their PB1 segment from a shared ancestor that existed before H5N1 reached the continent.
Researchers also noted that only a few amino acid differences separated the PB1 proteins of the H11N2 and H5N1 viruses, although the biological significance of these differences remains unknown. The discovery underscores the importance of monitoring not only dangerous H5N1 viruses but also apparently harmless low pathogenic influenza viruses that may serve as reservoirs of important genetic material.
The detection occurred months before Brazil reported its first H5N1 outbreak and years before the country's first commercial poultry farm outbreak, demonstrating how surveillance of wild birds can provide valuable early warning of changing viral populations.
Conclusion
The study shows that low pathogenic avian influenza viruses are actively exchanging genetic material with lineages linked to highly pathogenic H5N1 viruses in migratory bird populations. Although no highly pathogenic virus was detected in this investigation, the presence of an H5N1-related PB1 gene inside an H11N2 virus illustrates the complex evolutionary processes occurring in nature. Continuous genomic surveillance of migratory birds across underrepresented regions such as South America will be essential for detecting emerging viral combinations early, improving outbreak preparedness, protecting poultry industries, and strengthening global monitoring of influenza evolution before new threats become established.
The study findings were published in the peer reviewed journal: Viruses.
https://www.mdpi.com/1999-4915/18/7/710
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Read Also:
https://www.thailandmedical.news/articles/h5n1-avian-flu
https://www.thailandmedical.news/articles/influenza-or-flu
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