Simultaneous environmental and human surveillance for avian influenza viruses A, H5, H7, H9 and H10 in East, Central and Southwest China

Background The recent global rise in AIV outbreaks underscores the risk of transmission to humans. This study conducted surveillance to assess AIV circulation in poultry-related environments and patients with PUE in China. Methods From December 2021 to December 2023, we conducted AIV surveillance in LPMs, slaughterhouses, and poultry farms/backyards, alongside hospitalized PUE patients in East (City A, Nanping city), Central (City B, Luoyang city) and Southwest (City C, Chongqing) China. rRT-PCR was used to detect influenza A, with subtyping for H5, H7, H9, and H10. The median monthly positivity rate of AIVs was calculated, and differences in detection frequency were analyzed using Chi-square tests. Results Of 8,335 environmental specimens, the median monthly positivity rate for influenza A was 32.6%, with H5 at 6.9% and H9 at 18.4%. H5 was more frequently detected in Chongqing (13.5%), while H9 was highest in Nanping city (25.4%). LPMs and slaughterhouses showed higher positivity rates than farms/backyards, with blood wastewater and cutting board swabs more frequently contaminated than fecal samples and drinking water. Six H10 samples were detected, but no H7. Among 840 PUE respiratory specimens, 86 tested positive for seasonal influenza A, but no human AIV infections were identified. Conclusion Despite global AIV spread, no significant changes in AIV circulation were observed, and no human infections were detected. H9 remained the dominant subtype, highlighting the need to enhance poultry vaccination. Strengthening bio-security in LPMs and protecting occupationally exposed workers is recommended.