{"doi":"10.3389/fmicb.2023.1243567","title":"Human-to-swine introductions and onward transmission of 2009 H1N1 pandemic influenza viruses in Brazil","abstract":"Introduction: Once established in the human population, the 2009 H1N1 pandemic virus (H1N1pdm09) was repeatedly introduced into swine populations globally with subsequent onward transmission among pigs. Methods: To identify and characterize human-to-swine H1N1pdm09 introductions in Brazil, we conducted a large-scale phylogenetic analysis of 4,141 H1pdm09 hemagglutinin (HA) and 3,227 N1pdm09 neuraminidase (NA) gene sequences isolated globally from humans and swine between 2009 and 2022. Results: Phylodynamic analysis revealed that during the period between 2009 and 2011, there was a rapid transmission of the H1N1pdm09 virus from humans to swine in Brazil. Multiple introductions of the virus were observed, but most of them resulted in self-limited infections in swine, with limited onward transmission. Only a few sustained transmission clusters were identified during this period. After 2012, there was a reduction in the number of human-to-swine H1N1pdm09 transmissions in Brazil. Discussion: The virus underwent continuous antigenic drift, and a balance was established between swine-to-swine transmission and extinction, with minimal sustained onward transmission from humans to swine. These results emphasize the dynamic interplay between human-to-swine transmission, antigenic drift, and the establishment of swine-to-swine transmission in shaping the evolution and persistence of H1N1pdm09 in swine populations.","journal":"Frontiers in Microbiology","year":2023,"id":332070,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":26,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.8575,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2023-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":1058066,"name":"Caroline Tochetto","orcid":"0000-0002-9804-6175","position":1,"is_corresponding":false},{"id":347379,"name":"Tavis K. Anderson","orcid":"0000-0002-3138-5535","position":2,"is_corresponding":false},{"id":1058067,"name":"Danielle Gava","orcid":"0000-0002-1917-2633","position":3,"is_corresponding":false},{"id":1058068,"name":"Vanessa Haach","orcid":"0000-0001-5399-4107","position":4,"is_corresponding":false},{"id":1058069,"name":"Maurício Egídio Cantão","orcid":"0000-0002-5988-6542","position":5,"is_corresponding":false},{"id":896342,"name":"Amy L. Vincent","orcid":"0000-0002-4953-7285","position":6,"is_corresponding":false},{"id":1058070,"name":"Rejane Schaefer","orcid":"0000-0002-3511-0221","position":7,"is_corresponding":false},{"id":954949,"name":"Dennis Maletich Junqueira","orcid":"0000-0003-1576-484X","position":0,"is_corresponding":true}],"reference_count":67,"raw_metadata":null,"created_at":"2026-07-19T01:09:30.139849Z","pmid":"37614592","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}