[Correspondence] Duck-origin H5N6 avian influenza threatens public health: a challenge for poultry vaccination in China

Since 2021, H5 avian influenza viruses (AIVs) have caused widespread outbreaks among birds and mammals worldwide.1 In China, three fatal human H5N6 infections were reported in 2024 (two in Fujian and one in Anhui), with epidemiological investigations confirming direct contact with domestic poultry.2 A 2025 study identified a novel duck-origin H5 virus with enhanced affinity for human-type receptors,3 underscoring the increasing public threat posed by duck H5 AIVs. We showed that all the three human isolates were closely related to duck-origin H5N6 viruses (appendix pp 1, 6–14, 16).