Background: No studies have deeply examined the transmission patterns of H1N1pdm09 in Anhui Province, China. Methods: We conducted a genome-wide analysis of 162 historical epidemic strains in Anhui Province, China to understand the transmission patterns, incoming and outgoing events, and evolutionary dynamics of the strains. Results: Our study showed that the number of recent infections was higher in 2018-2023 compared to previous years. Compared to the global strain sequences, the clade production times were all delayed in Anhui Province, China, suggesting that Anhui is an introduced region in the global transmission chain. The NA fragments had higher dN/dS values than the HA fragments. The circulation pattern of the strain in Anhui Province, China was mainly from central to northern, followed by northern to central and central to southern. Central Anhui was the transmission center of H1N1pdm09 in Anhui Province, China. Calculation of transmission events for the whole country showed that the main source of the epidemic strain in Anhui Province was East China, but the national epidemic of the H1N1pdm09 strain in 2023 appeared to originate from Anhui Province, China. Conclusion: The above results emphasize the focus of influenza prevention and control in Anhui Province, China, as well as the importance of sharing information about epidemics between different provinces.

In the context of the COVID-19 pandemic, we investigated the epidemiological and clinical characteristics in a young patient infected by avian influenza A (H5N6) virus in Anhui Province, East China, and analyzed genomic features of the pathogen. Through the cross-sectional investigation of external environment monitoring (December 29-December 31, 2020), 1 909 samples were collected from Fuyang City. It was found that the positive rate of H5N6 in Tianma poultry market was higher than other areas obviously, where the case appeared. The virus was the clade 2.3.4.4, which was most likely formed by genetic reassortment between H5N6 and H9N2 viruses. This study found that the evolution rates of HA gene and NA gene of the virus were higher than those of common seasonal influenza viruses. The virus was still highly pathogenic to poultry, and had a preference for avian receptor binding.

Objective In China, H9N2 avian influenza viruses were first reported in chickens in Guangdong province in the mid-1990s. Subsequently, the viruses spread to most regions nationwide, where they became panzootic and endemic. Based on environmental surveillance of live poultry markets in Anhui province from 2013 to 2018, a total of 33 representative environmental isolates were selected and studied systematically. Methods The genomic RNA of Anhui H9N2 isolates was subjected to RT-PCR amplification followed by sequencing analysis. Results Thirty-three strains were isolated from the embryonated eggs of specific-pathogen-free chickens. Phylogenetic analysis indicated that h9.4.2.5-like H9N2 viruses were predominant during 2013--2018 and acquired multiple specific amino acid mutations that may have increased their affinity for mammals and enhanced their infectivity and transmissibility. Additionally, six internal genes of H9N2 clustered together with the novel human-lethal reassortant viruses, such as low pathogenicity H7N9, H10N8 and Anhui H5N6 viruses, and even HPAI H7N9. Conclusion Because H9N2 viruses may be the donors of internal genes that lead to the generation of novel reassortant viruses with enhanced pathogenicity in Anhui province, continuous environmental surveillance of live poultry markets, a key source of reassorted H9N2 and other avian influenza viruses, is of great importance.