Swine play a key role in the ecology and transmission of influenza A viruses (IAVs) between species. However, the epidemiology and diversity of swine IAVs is not completely understood. In this cohort study, we sampled on a weekly basis 132 3-week old pigs for 15 weeks. We found two overlapping epidemic events of infection in which most pigs (98.4%) tested PCR positive for IAVs. The prevalence rate of infection ranged between 0 and 86% per week and the incidence density ranged between 0 and 71 cases per 100 pigs-week. Three distinct influenza viral groups (VGs) replicating as a "swarm" of viruses were identified (swine H1-gamma, H1-beta, and H3-cluster-IV IAVs) and co-circulated at different proportions over time suggesting differential allele fitness. Furthermore, using deep genome sequencing 13 distinct viral genome constellations were differentiated. Moreover, 78% of the pigs had recurrent infections with IAVs closely related to each other or IAVs clearly distinct. Our results demonstrated the molecular complexity of swine IAVs during natural infection of pigs in which novel strains of IAVs with zoonotic and pandemic potential can emerge. These are key findings to design better health interventions to reduce the transmission of swine IAVs and minimize the public health risk.
Bibliographical noteFunding Information:
The authors would like to acknowledge My Yang and Drs. Victor Neira and Macarena Cortez for their help collecting and processing samples during this study; the National Pork Board (NPB-12–068) and the Departamento Administrativo de Ciencia, Tecnologia e Innovación COLCIENCIAS (Becas Caldas) for their funding; and the Minnesota Supercomputing Institute (MSI) at the University of Minnesota. The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.