Objective:To analyze and reveal the genetic evolution and variation of influenza viruses in cases of co-infection in Guangdong Province.Methods:Throat swab samples were collected from four cases of H1N1pdm and H3N2 co-infection for viral isolation. The isolated strains were subjected to antigen analysis and neuraminidase inhibitor susceptibility test. High-throughput sequencing was used to detect the sequences of strains in three throat swab samples and one virus strain, and then genetic variations were analyzed.Results:Four influenza viruses were isolated with one strain of H1N1pdm and three of H3N2 subtype, and all of them were genetically similar to the vaccine strain in 2022-2023. The HA genes of H1N1pdm and H3N2 strains belonged to clade 6B.1A.5a.2a and 2a.3a.1, respectively. The isolated strains belonged to the same clade as the strains prevalent in Guangdong during the same period. No drug-resistant variations were detected in N1 or N2 gene, and the isolated strains were sensitive to oseltamivir and zanamivir.Conclusions:H1pdm subtype had stronger replication ability than H3 subtype in the influenza viruses isolated from co-infected cases. H1N1pdm and H3N2 subtype influenza viruses were genetically similar to the strains circulating in Guangdong at the same time. The isolated H1N1pdm and H3N2 strains were sensitive to both oseltamivir and zanamivir, indicating that they could continue to be used in the treatment of influenza virus infections caused by one or two genotypes.

Objective To investigate the infection status and epidemiological characteristics of viral pathogens in hospitalized patients with severe acute respiratory infection (SARI) in Guangdong Province from 2019 to 2021, so as to provide reference for clinical diagnosis and prevention. Methods The respiratory tract samples of SARI patients collected from 2019 to 2021 were detected and analyzed for respiratory syncytial virus (RSV), adenovirus (ADV), human rhinovirus/enterovirus (HRV/EV), human metapneumonic virus (HMPV) and other common respiratory viruses using Luminex respiratory multi-pathogen detection technology. Results A total of 1 948 influenza-negative cases were collected, of which 24.28 % were positive detection of virus infection. HRV/EV was the highest (10.32%), followed by RSV (4.31%). The detection rates were statistically significantly different among different age groups (χ²=176.186，P<0.05), and the highest detection rate was found in the group aged at 0 to 4 years (41.50%). There was no statistically significant between the male virus detection rate and the female virus detection rate (χ²=0.042，P>0.05). The detection peaks of RSV were mainly concentrated in summer and autumn, while HMPV was prevalent in winter, and HRV/EV and ADV had no obvious seasonality. Mixed infection was found in 39 samples, and the mixed infection rate was 2.00%. In the mixed infection cases, HPIV and HRV/EV combined infection was the most common. Conclusion HRV/EV, RSV, HMPV and ADV are predominant viral pathogens in SARI influenza-negative hospitalized cases in Guangdong Province from 2019 to 2021. It is recommended to strengthen the surveillance of SARI cases in children under 5 years old.