A new Chinese study provides one of the clearest long-term pictures yet of occupational exposure to multiple avian influenza virus subtypes around Poyang Lake, a major poultry and migratory-bird interface in Jiangxi Province. Across 2,437 serum samples collected from 2018 to 2025, researchers detected variable antibody reactivity to H5N6, H9N2, H7N9, H3N8, H10N3 and H5N8... but none to H5N1 in the 600 samples tested during 2024–2025.
The study focused on backyard poultry keepers, their household members and live-poultry-market workers in Nanchang and Jiujiang. Poyang Lake is particularly important because it lies on the East Asian–Australasian Flyway and combines dense poultry production, live-bird markets, wild-bird populations and frequent human exposure. Previous environmental surveillance in Jiangxi has reported avian influenza positivity rates as high as 82.3%, making the region a major surveillance hotspot.
H5N6 and H9N2 produced the highest overall antibody reactivity
Among the 2,437 valid serum samples, 108 (4.43%) met the predefined haemagglutination-inhibition threshold for H5N6, while 107 (4.39%) met the threshold for H9N2. The pattern varied substantially by year and location. H5N6 reactivity peaked in Jiujiang in 2021 and in Nanchang in 2022, while H9N2 peaked in Jiujiang in 2021 and Nanchang in 2023. These fluctuations suggest changing exposure patterns rather than a stable background seroprevalence.
H9N2 is especially relevant because it circulates extensively in poultry in China, often without producing severe disease in birds, creating repeated opportunities for occupational exposure.
H3N8 and H10N3 signals emerged in 2024
The most notable newer findings involved H3N8 and H10N3. Among samples collected from 2021–2025, 22 of 1,523, or 1.44%, were reactive to H3N8. In Nanchang during the 2024 surveillance year, however, 9% met the positivity threshold, a marked local increase.
H10N3 reactivity was much rarer: only four of 1,523 samples, or 0.26%, were positive, but all four came from Jiujiang in 2024.
The authors specifically identify both the Nanchang H3N8 signal and the Jiujiang H10N3 findings as deserving further investigation.
H7N9 antibodies persisted after the major epidemic period
H7N9 was assessed mainly during the earlier surveillance period. Between 2018 and 2020, 25 of 914 samples (2.74%) met the antibody threshold for H7N9. The finding is epidemiologically relevant because Poyang Lake and surrounding poultry markets had previously experienced substantial H7N9 activity, including human cases in Nanchang in 2017.
No H5N1 antibody reactivity detected in 2024–2025
One of the most striking results is what the study did not find. Among 600 serum samples tested for H5N1 during the 2024 and 2025 surveillance years, none met the predefined positivity threshold. That finding should not be interpreted as proof that H5N1 exposure did not occur in the region. Haemagglutination-inhibition titres can decline over time, testing thresholds affect sensitivity, and not every infection produces a detectable persistent HI response. But within this surveillance population, the study did not identify measurable H5N1 antibody reactivity despite the global expansion of H5 viruses.
Environmental virus circulation is much higher than human antibody detection
The human serology needs to be interpreted alongside exceptionally high environmental and poultry virus detection around Poyang Lake.
A separate eight-year surveillance study covering 2017–2024 analysed 7,570 poultry and environmental samples in the southwestern Poyang Lake region. Overall avian influenza virus positivity reached 40.1%, with poultry positivity of 42.1% and environmental positivity of 38.0%. By 2024, positivity had risen to 69.4% in poultry and 77.7% in environmental samples. H9 viruses dominated those detections, with an overall H9 positivity rate of 26%.
This contrast is important: very high virus circulation in poultry and market environments does not translate into equally high measurable seropositivity in humans. Spillover therefore appears frequent enough to leave detectable signals, but still much less common than exposure to contaminated poultry environments.
Seropositivity is not the same as confirmed infection
The authors are careful about interpretation. Haemagglutination-inhibition antibody reactivity alone does not prove a subtype-specific human infection, because cross-reactivity between influenza viruses is possible and the study did not rely on confirmatory microneutralisation for all samples. The study is also cross-sectional rather than a cohort following the same individuals over time, and the number of samples tested differed between subtypes and years.
The findings are therefore best understood as signals of past immunological exposure, not a direct count of infections.
A surveillance hotspot where poultry, wild birds and humans converge
Poyang Lake illustrates precisely why One Health surveillance is needed. Migratory birds, domestic poultry, live-poultry markets and occupationally exposed people share the same ecological system. The new study shows that this interface produces repeated human antibody signals across several avian influenza subtypes, including viruses with documented zoonotic potential.
The authors therefore recommend continued serological surveillance combined with poultry testing, environmental virology and molecular characterisation of circulating viruses.
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