Genetic characterization of two novel picornaviruses from birds, white-tailed eagle (Haliaeetus albicilla) and pied avocet (Recurvirostra avosetta) in Hungary

Hidden Viruses in Familiar Birds

Birds such as eagles and wading shorebirds are striking symbols of wetlands, but they also quietly carry entire worlds of microbes within them. This study explores that invisible world by uncovering two previously unknown viruses living in a white-tailed eagle and a pied avocet in Hungary. Although these birds appeared healthy, the viruses in their intestines turned out to be so unusual that they may represent entirely new branches on the virus family tree. Discoveries like this help scientists understand how wildlife harbors and spreads viruses, and how those viruses evolve over time.

What Kind of Viruses Were Found?

The newly discovered agents belong to the picornaviruses, a large family of tiny RNA viruses that also includes several important human and animal pathogens. Picornaviruses package their genetic material as a single long strand of RNA, which is read by the host’s cells as one giant protein that later gets cut into functional pieces. By using high-throughput sequencing and targeted follow-up tests, the researchers assembled nearly complete genomes of two such viruses from harmless cloacal swabs: one from a white-tailed eagle and one from a pied avocet. Both viruses showed the classic overall layout of picornaviruses, confirming they belonged to this family despite showing strong genetic differences from any strains described before.

Looking Closely at Viral Blueprints

To place these viruses on the virus family tree, the team compared key protein-coding regions with those of known picornaviruses. These regions encode the outer shell that forms the virus particle, and the internal machinery that copies the RNA and processes viral proteins. In both the eagle and avocet viruses, these proteins shared less than half of their amino acid sequences with their closest known relatives from bird and bat samples. In virus classification, gaps this large typically signal that one is dealing not just with new strains, but potentially with new species or even new genera—entirely fresh lineages within the broader group.

Unusual Control Regions in the Viral Genome

Beyond the protein-coding parts, the scientists examined the non-coding ends of the viral RNA, which act as control hubs for how efficiently the virus makes proteins and replicates. At the front end of the genome, both viruses carried a specialized structure that lets them hijack the host’s protein-making machinery without using the usual “cap” signal found on most cellular RNAs. This structure resembled a known “type III” entry site seen in hepatitis A–like viruses, but was missing one of its standard domains, suggesting an alternative way of achieving the same trick. At the tail end, the avocet virus showed multiple repeated sequence motifs that folded into distinct loops, while the eagle virus had a region unusually rich in one type of nucleotide. These patterns had no close matches in existing databases, highlighting how distinct these viruses are from their relatives.

Why Wetlands and Migratory Birds Matter

When the researchers compared these genomes with other bird viruses, a broader pattern emerged. The new viruses clustered in a subgroup of picornaviruses that includes many species found in wild waterbirds and other animals living in or around aquatic habitats. Many of these hosts are migratory, regularly moving between continents. The eagle and avocet viruses fit neatly into this picture: both hosts use wetland environments and long-distance movements, creating opportunities to share viruses with other species. Yet the infected birds in this study appeared healthy, so the ecological roles and health impacts of these viral lineages remain unclear.

What This Means Going Forward

Overall, the study shows that a simple swab from a wild bird can reveal entire new branches of the viral world. The eagle and avocet viruses are so genetically distinct, and occupy such separate positions on the virus family tree, that they likely represent founding members of two new groups within the picornaviruses. For non-specialists, the takeaway is that healthy wild birds quietly host a rich diversity of viruses that we are only beginning to map. Understanding these hidden communities is essential for tracking how viruses evolve, how they move across species and borders, and which of them—if any—might one day pose risks to wildlife, domestic animals, or humans.

Citation: Balázs, B., Boros, Á., Pankovics, P. et al. Genetic characterization of two novel picornaviruses from birds, white-tailed eagle (Haliaeetus albicilla) and pied avocet (Recurvirostra avosetta) in Hungary. Sci Rep 16, 9816 (2026). https://doi.org/10.1038/s41598-026-39780-1

Keywords: wild bird viruses, picornaviruses, avian microbiome, wetland ecology, viral evolution