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Volume 32, Number 8—August 2026

Dispatch

Isolation of Infectious Highly Pathogenic Avian Influenza A(H5N1) Virus from Fetal Bovine Serum, United States, 2025

Ana R. Rebelo1, Erica Buttler1, Elizabeth Aguilera Nunez, Brittany Cronk, Jennifer Powers, Melissa Laverack, Chen Feng, Mohammed Nooruzzaman, Mia K. Torchetti, Leonardo C. Caserta, and Diego G. DielComments to Author 
Author affiliation: Cornell University College of Veterinary Medicine, Ithaca, New York, USA (A.R. Rebelo, E. Buttler, E. Aguilera Nunez, B. Cronk, J. Powers, M. Laverack, C. Feng, M. Nooruzzaman, L.C. Caserta, D.G. Diel); US Department of Agriculture Animal and Plant Health Inspection Service, Ames, Iowa, USA (M.K. Torchetti)

Main Article

Figure 1

Phylogenetic analysis of complete genomes formed by concatenation of all gene segments, confirming highly pathogenic avian influenza A (H5N1) virus genotype B3.13 isolated from fetal bovine serum (FBS), United States, 2025. A) Tree showing broader phylogeny of H5N1 virus genotypes. B) Closer examination of the virus from FBS sample and closely related virus sequences. Dashed lines indicate the branch in the broader phylogenetic tree where the FBS virus sequence is located. Dataset consisted of 5,094 highly pathogenic avian influenza A(H5N1) virus genomes from samples collected during August 2024–January 2025 in North America, downloaded from the GISAID EpiFlu database (5). Maximum-likelihood phylogenetic inferred with an edge-linked partition model and 1,000 bootstrap replicates using IQ-TREE (6).

Figure 1. Phylogenetic analysis of complete genomes formed by concatenation of all gene segments, confirming highly pathogenic avian influenza A (H5N1) virus genotype B3.13 isolated from fetal bovine serum (FBS), United States, 2025. A) Tree showing broader phylogeny of H5N1 virus genotypes. B) Closer examination of the virus from FBS sample and closely related virus sequences. Dashed lines indicate the branch in the broader phylogenetic tree where the FBS virus sequence is located. Dataset consisted of 5,094 highly pathogenic avian influenza A(H5N1) virus genomes from samples collected during August 2024–January 2025 in North America, downloaded from the GISAID EpiFlu database (5). Maximum-likelihood phylogenetic inferred with an edge-linked partition model and 1,000 bootstrap replicates using IQ-TREE (6).

Main Article

References
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1These first authors contributed equally to this article.

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