Recurrent spillover of H5 avian influenza to vampire bats (Desmodus rotundus) at the marine-terrestrial interface

The adaptability of H5N1 clade 2.3.3.4b avian influenza to mammals has raised pandemic concerns. While most infected mammals lack their own influenza viruses, reducing reassortment risk, bats harbour influenza strains like H18N11, creating the potential for co-infection and reassortment. The 2022 H5N1 epizootic caused mass mortality in seabirds and South American sea lions along the Peruvian coast. Here, we integrated ecological and virological approaches to explore the H5N1 exposure risk in common vampire bats, which blood-feed on livestock and marine wildlife. We tested bat serum samples over 8 years (2011-2024) from 12 Peruvian sites, including coastal roosts with (<100 m from the sea, N=431 bats)/without (>5 km, N=373) marine contact, and inland roosts (N=57). An ELISA detected anti-H5 antibodies in 14 individuals from marine-contact sites exclusively across multiple years, though qRT-PCR found no influenza RNA in corresponding swabs, suggesting sporadic and recurring exposures. H18 was prevalent in the region; three H5-positive bats were also H18-positive, underscoring co-infection risk. Stable isotope analysis of bat hair linked seropositive bats to marine diets (δ15N 23.75 ± 0.62‰), while negatives had lower δ15N, suggesting livestock or mixed diets. Metabarcoding confirmed that seropositive bats fed on H5N1-impacted species, such as sea lions and cormorants. Additionally, vampire bat cells were permissive to avian influenza viruses, supporting infection potential. Our findings provide the first evidence of H5 exposure in bats. Repeated viral exposures, cellular permissiveness and co-infection with other influenza A viruses highlight the potential for vampire bats to act as novel H5 reservoirs or facilitate spillover.

I-Ting Tu1,2, Christina Lynggaard3, Sarah Walsh2, Lorin Adams4, Savitha Raveendran2, Matthew Turnbull2, Megan Griffiths1,2, Carlos Tello5, William Valderrama Bazan5, Jan Felix Drexler6, Christina Faust1, Susana Cárdenas-Alayza7, Ed Hutchinson2, Pablo Murcia2, Kristine Bohmann3, Ruth Harvey4, Daniel Streicker1,2 1School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK 2MRC-University of Glasgow Centre for Virus Research, Glasgow, UK 3Globe Institute, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark 4Worldwide Influenza Centre, The Francis Crick Institute, London, UK 5Asociación para el Desarrollo y Conservación de los Recursos Naturales (Illariy), Lima, Perú 6Charité Universitätsmedizin, Berlin, Germany 7Centro para la Sostenibilidad Ambiental, Universidad Peruana Cayetano Heredia, Lima, Perú

Late Breaking