Zoonotic influenza preparedness: Dutch medical labs efficiently detect animal influenza A viruses - External Quality Assessment, 2023

BACKGROUND: Since 2022, highly pathogenic H5N1 influenza A virus clade 2.3.4.4b has caused global outbreaks among wild birds and poultry, with increasing mammalian and sporadic human infections. This elevates concerns about zoonotic transmission and pandemic risk, highlighting the need for accurate detection and identification of animal influenza A viruses by human clinical diagnostic laboratories (hCDL). METHODS: To evaluate routine diagnostic performance, an External Quality Assessment (EQA) panel containing inactivated influenza A viruses of avian (three subtype H5, one H7), swine (two H1, one H3), and human (one H1pdm09, one H3) origin was distributed to 50 hCDL in the Netherlands, Aruba, Bonaire, and Curaçao. Laboratories conducted their routine molecular influenza virus detection and, if available, subtyping workflows. RESULTS: A total of 118 detection workflows were reported. Of these, 109 (91 %) successfully detected influenza A virus in all positive specimens. At least one workflow in 49/50 (98 %) laboratories reliably detected all animal influenza viruses as type A influenza virus. Most false negatives occurred with swine H1N1v. Only 24 workflows from 20 laboratories attempted subtyping for one or multiple panel specimens (total 109 subtype-specific results reported): for human viruses, 37/39 results were correct; for avian viruses, 13/14 were correct (including 12/12 for H5); for swine viruses, only 2/56 were correct (both swine H3N2 using broad-reactive H3 assays). CONCLUSIONS: hCDL in the Netherlands demonstrate high performance for detecting animal influenza A viruses. However, subtyping capacity is limited, necessitating referral of specimens of suspected zoonotic influenza cases to the National Influenza Centre for further characterization.