Implications for influenza A virus surveillance in Southeast Asian Region countries: a scoping review of approaches for the surveillance of swine influenza viruses at human-swine interfaces.

Background and objectives: The Southeast Asian Region (SEAR) faces a heightened risk of reassortment of circulating influenza viruses in swine populations due to the dense cohabitation of humans, poultry and swine. However, there is currently no specific guidance on conducting influenza surveillance at the human-swine-poultry interfaces within SEAR. This study conducted a scoping review to characterise the objectives and frameworks of influenza A Virus (IAV) surveillance systems established at human-swine exposure sites globally. Design: A literature search was performed for studies published until June 2024 that reported on IAV survey and surveillance activities at swine farms, slaughterhouses, agricultural fairs, animal markets, backyard farms and among swine workers. Data sources and extraction: Data were extracted from relevant articles using PubMed, Scopus and Web of Science, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for scoping reviews. Extracted data were organised in MS Excel, with analyses stratified by IAV surveillance objectives. Results: Of 42 studies meeting inclusion criteria, most were short-term and project-based. Half of the studies (50%; 21/42) were conducted in Asia, strongly focusing on virological monitoring as the main surveillance objective (69%; 29/42). Swine farms were the primary setting for surveillance (61.90%; 26/42), with active surveillance employed in most cases (90.48%; 38/42). Sampling techniques included nasal, tracheal and faecal swabs, along with serum and lung tissue, with most sampling targeting swine (73.81%). Other targets included swine and humans (11.90%); swine, humans and environmental samples (7.14%); humans only (4.76%); and swine and poultry (2.38%). Testing relied heavily on PCR and whole-genome sequencing, used by half of the studies (50%; 21/42) alongside RT-PCR and ELISA for detecting IAVs. Conclusion: This study reveals considerable variability in IAV survey and surveillance across human-swine-poultry interfaces. Establishing standardised, objective-based protocols for such surveillance is crucial to strengthening IAV's global preparedness and response capabilities and benchmarking progress towards zoonotic risk reduction.