Seroprevalence of Avian Influenza Viruses (H5N1 and H9N2) Among Poultry Workers and Live Bird Market Vendors in Asia: A Systematic Review and Meta-Analysis

Background

Occupationally exposed poultry workers and live bird market (LBM) vendors represent a major zoonotic interface for avian influenza transmission in Asia. To our knowledge, no prior PRISMA 2020-compliant meta-analysis has concurrently pooled H5N1 and H9N2 seroprevalence estimates in this occupational population across Asia.

Methods

A systematic review and meta-analysis was conducted following PRISMA 2020 guidelines (PROSPERO: CRD420261380328). PubMed, Google Scholar, and Elicit were searched from inception to 10 May 2026. Eligible studies reported serological evidence, assessed by haemagglutination inhibition (HI) or microneutralisation (MN) assay, of H5N1 or H9N2 infection among Asian occupationally exposed poultry workers and LBM vendors. Risk of bias was assessed using the JBI Critical Appraisal Checklist. Pooled seroprevalence was estimated using a DerSimonian–Laird random-effects model with Freeman–Tukey double-arcsine transformation. Publication bias was evaluated using Egger's test.

Results

Of 70 records identified, 22 studies met eligibility criteria (21 included in meta-analysis), spanning seven countries and 26,413 participants. Eight studies were rated low risk of bias and 12 moderate. Pooled seroprevalence was 2.38% (95% CI: 0.62–5.23%; I²=84.8%) for H5N1 and 11.79% (95% CI: 5.96–19.27%; I²=96.9%) for H9N2. Subgroup analysis revealed marked regional variation: South Asian studies yielded H9N2 seroprevalence of 24.9% (95% CI: 10.3–49.0%) approximately four-fold higher than East Asia (5.9%, 95% CI: 2.8–11.9%). Sensitivity analyses yielded lower pooled estimates of 0.71% (H5N1) and 4.44% (H9N2). No publication bias was detected for H5N1 (p=0.798); H9N2 asymmetry (p=0.002) may reflect regional and small-study effects rather than publication bias.

Conclusions : Avian influenza seroprevalence among occupationally exposed poultry workers and LBM vendors in Asia is notable, particularly H9N2 in South Asia. The marked four-fold regional variation in H9N2 seroprevalence, combined with persistently high heterogeneity, points to the need for region-specific occupational surveillance programmes and standardised serological protocols. Strengthening One Health frameworks,and expanding seroepidemiological coverage to underrepresented settings would contribute to pandemic preparedness strategies in high-risk poultry-exposed populations.