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#Isolation and Characterization of #H1 Subtype #Swine #Influenza Viruses Recently Circulating in #China

Abstract Pigs serve as a mixing vessel for influenza viruses and can independently promote the emergence of pandemic strains in humans. During our surveillance of pig populations from 2021 to 2023 in China , 11 H1 subtype swine influenza viruses (SIVs) were isolated. All viruses were reassortants , possessing internal genes of identical origins ( PB2, PB1, PA, NP, M : pdm09/H1N1 origin, NS : North American triple reassortant origin). The H1N1 isolates were all the dominant G4 EA H1N1 viruses in China. Two H1N2 isolates carried early human pdm09/H1N1 HA genes, suggesting a possible pig-to-human transmission route. Mutations that dictate host range specificity were identified in all isolates, a phenomenon which may enhance the affinity to human receptors. These H1 subtype viruses effectively replicated both in vivo and in vitro without prior adaptation and exhibited different pathogenicity and growth characteristics. Some of the H1 viruses were even found to cause lethal infections in mi...

Novel introductions of #human-origin #H3N2 #influenza viruses in #swine, #Chile

Abstract Influenza A virus (IAV) continuously threatens animal and public health globally , with swine serving as a crucial reservoir for viral reassortment and evolution . In Chile , H1N2 and H3N2 subtypes were introduced in the swine population before the H1N1 2009 pandemic, and the H1N1 was introduced from the H1N1pdm09 by successive reverse zoonotic events . Here, we report two novel introductions of IAV H3N2 human-origin in Chilean swine during 2023. Our study reveals a closer relationship between recent human seasonal H3N2 and novel swine strains. Interestingly, one strain maintains all the genes from the original human virus , but the other strain is already a reassortment of human H3N2 and an H1N2 previously observed on the farm. Observing global IAV sequences, a similar pattern was identified in the USA confirming the reverse zoonotic potential of current seasonal human H3N2 strains. These results highlight the importance of ongoing surveillance and reinforcing biosecurity in ...