Rapid increase in antibodies to influenza A virus H5 and N1 in Lesser Scaup (Aythya affinis) following the introduction of 2.3.4.4B H5N1 into North America

Jeffery D. Sullivan; Rebecca L. Poulson; Glenn H. Olsen; Alicia Berlin; Zijing Cao; Deborah Carter; Josh Homyack; Jennifer Kilburn; Scott R. McWilliams; Joshua Osborn; Tori Mezebish Quinn; Hannah Schley; Matthew M. Weegman; Christopher A. Williams; David E. Stallknecht; Diann Prosser

doi:10.1139/cjm-2025-0176

Rapid increase in antibodies to influenza A virus H5 and N1 in Lesser Scaup (Aythya affinis) following the introduction of 2.3.4.4B H5N1 into North America

Canadian Journal of Microbiology

By: Jeffery D. Sullivan, Rebecca L. Poulson, Glenn H. Olsen, Alicia Berlin, Zijing Cao, Deborah Carter, Josh Homyack, Jennifer Kilburn, Scott R. McWilliams, Joshua Osborn, Tori Mezebish Quinn, Hannah Schley, Matthew M. Weegman, Christopher A. Williams, David E. Stallknecht, and Diann Prosser

https://doi.org/10.1139/cjm-2025-0176

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Abstract

Clade 2.3.4.4b Eurasian-origin H5N1 entered North America in late 2021 and spread across the continent. While studies have characterized the antibody response mounted by dabbling ducks following exposure, little data are available for diving ducks. This study sought to identify influenza A virus (IAV) infection and antibodies in Lesser and Greater Scaup captured in Maryland, Illinois, and Rhode Island. In Maryland, IAV seroprevalence increased from the 2021/2022 to 2022/2023 sampling season, with IAV antibody prevalence increasing for juvenile (38% to 80%) and adult (82% to 90%) Lesser Scaup. While adult Lesser Scaup sampled in Illinois in 2021/2022 had IAV antibody prevalence comparable to those sampled in Maryland (76% and 82%, respectively), they had higher antibody prevalence to both H5 (48% and 18%) and N1 (68% and 35%), potentially due to being sampled in March versus December and January. Our data suggest that Lesser Scaup had limited antibodies to highly pathogenic H5 IAV prior to the introduction of clade 2.3.4.4b H5N1 to North America, but relevant antibodies were widely observed in the months and year following. Our more limited data suggest similar trends may have occurred in Greater Scaup as well.

Additional publication details
Publication type	Article
Publication Subtype	Journal Article
Title	Rapid increase in antibodies to influenza A virus H5 and N1 in Lesser Scaup (Aythya affinis) following the introduction of 2.3.4.4B H5N1 into North America
Series title	Canadian Journal of Microbiology
DOI	10.1139/cjm-2025-0176
Edition	Online First
Publication Date	November 13, 2025
Year Published	2025
Language	English
Publisher	Canadian Science Publishing
Contributing office(s)	Eastern Ecological Science Center