Objectives
The adaptation of clade 2.3.4.4b influenza A(H5N1) to dozens of mammalian species, including dairy cattle, raises concerns about potential spillover into humans. If the virus develops human-to-human transmissibility, sensitive diagnostics will be critical to containment efforts. We sought to determine the lower limit of detection of commercial influenza A tests for the circulating bovine-adapted strain of H5N1.

Methods
We determined the 95% lower limit of detection (LLOD) of 4 commercial respiratory virus panels for detecting inactivated bovine H5N1 (A/bovine/Ohio/B24OSU-439/2024). Two of the tested panels provide seasonal influenza A subtyping, the BioFire Respiratory Panel 2.1 (BioFire Diagnostics/BioMérieux) and the cobas eplex respiratory pathogen panel 2 (Roche Diagnostics), while 2 panels provide pan–influenza A detection, the Xpert Xpress CoV-2/Flu/RSV plus (Cepheid), and the Panther Fusion SARS-CoV-2/Flu A/B/RSV Assay (Hologic, Inc). Serial dilutions of H5 RNA (400-25 copies/mL) were prepared in respiratory virus–negative nasopharyngeal swab matrix, and 20 replicates were tested at each concentration. The 95% LLOD for each test was calculated using probit regression.

Results
All 4 tests detected H5 with 95% LLODs below 1000 H5 RNA copies/mL. Xpert demonstrated the highest analytical sensitivity (50 copies/mL; 95% CI, 39-160), followed by BioFire (297 copies/mL; 95% CI, 196-3955), Panther Fusion (531 copies/mL; 95% CI, 421-792), and eplex (883 copies/mL; 95% CI, 588-2741).

Conclusions
Existing commercial respiratory virus panels can effectively detect bovine H5N1. These platforms could support screening in the event of an H5N1 outbreak, followed by confirmation with specific H5 subtyping, as needed.