To monitor and analyze the molecular variation of the H3N2 influenza virus in Guangzhou during the COVID-19 pandemic, respiratory samples of influenza-like cases from influenza monitoring sentinel hospitals were collected from influenza monitoring sentinel hospitals for virus isolation and whole genome sequencing. The results showed that during COVID-19, there was only one peak of H3N2 influenza in the second quarter of 2022 in Guangzhou (the positive rate was 52.23%), and the epidemic intensity and duration were both higher than those in 2019. The HA gene and NA gene of the epidemic strain in Guangzhou in 2022 belonged to the 3C.2a1b. 2a. 1a. 1 branch, which had a good antigenic site matching with the vaccine strain (A/Cambodia/e0826360/2020) from 2021 to 2022 and had no antigen drift. In 2022 strains, the variation of antigen determinant mainly occurred in the I48T of C region, while no variation occurred in the A, B, D, and E regions. The binding site of the HA protein receptor was consistent with the vaccine strain (A/Cambodia/e0826360/2020). Most of the strains in 2022 carried 13 glycosylation sites on the HA protein, but an outbreak of strains caused a loss of glycosylation sites at 24-NST. In conclusion, the strains that caused the epidemic of H3N2 influenza in Guangzhou in 2022 were not evolved or transmitted from the local strains in 2019 during the COVID-19 pandemic.

To monitor and analyze the molecular variation of the H3N2 influenza virus in Guangzhou during the COVID-19 pandemic, respiratory samples of influenza-like cases from influenza monitoring sentinel hospitals were collected from influenza monitoring sentinel hospitals for virus isolation and whole genome sequencing. The results showed that during COVID-19, there was only one peak of H3N2 influenza in the second quarter of 2022 in Guangzhou (the positive rate was 52.23%), and the epidemic intensity and duration were both higher than those in 2019. The HA gene and NA gene of the epidemic strain in Guangzhou in 2022 belonged to the 3C.2a1b. 2a. 1a. 1 branch, which had a good antigenic site matching with the vaccine strain (A/Cambodia/e0826360/2020) from 2021 to 2022 and had no antigen drift. In 2022 strains, the variation of antigen determinant mainly occurred in the I48T of C region, while no variation occurred in the A, B, D, and E regions. The binding site of the HA protein receptor was consistent with the vaccine strain (A/Cambodia/e0826360/2020). Most of the strains in 2022 carried 13 glycosylation sites on the HA protein, but an outbreak of strains caused a loss of glycosylation sites at 24-NST. In conclusion, the strains that caused the epidemic of H3N2 influenza in Guangzhou in 2022 were not evolved or transmitted from the local strains in 2019 during the COVID-19 pandemic.

Objective:To understand the epidemiological characteristics of mpox epidemic in Guangzhou and provide scientific evidence for the prevention and control of the disease.Methods:Based on the mpox surveillance system in Guangzhou, suspected mpox cases with fever and rash were reported by local hospitals at all levels to centers for disease control and prevention in Guangzhou for sampling, investigation and diagnosis. Descriptive epidemiological analysis was conducted on the clinical characteristics and treatment of the mpox cases and positive detection rate reported in Guangzhou as of 24:00 on June 23. Whole genome sequencing of the virus isolates was performed using Illumina Miniseq high-throughput sequencing platform.Results:The first mpox case in Guangzhou was reported on June 10 in 2023. As of 24:00 on June 23, a total of 25 confirmed mpox cases were reported. All the mpox cases were men with a M( Q1, Q3) of 32 (26, 36) years, the majority of the cases were MSM (96.0%). The main clinical features were rash (100.0%, 25/25), lymphadenectasis (100.0%, 25/25) and fever (52.0%, 13/25). Rash usually occurred near the genitals (88.0%, 22/25). The close contacts, mainly family members (40.4%, 23/57), showed no similar symptoms, such as fever or rash. The positive rate of mpox virus in household environment samples was 30.5%. The analyses on 3 complete gene sequences of mpox virus indicated that the strains belonged to West African type Ⅱb clade, B.1.3 lineage. Conclusions:Hidden transmission of mpox virus had occurred in MSM in Guangzhou. However, the size of affected population is relatively limited, and the possibility of wide spread of the virus is low.

Objective:To identify a novel reassortant H3N2 avian influenza virus using nanopore sequencing technology and analyze its genetic characteristics.Methods:The positive samples of the H3N2 avian influenza virus, collected from the external environment in the farmers' market of Guangzhou, were cultured in chicken embryos. The whole genome was sequenced by targeted amplification and nanopore sequencing technology. The genetic characteristics were analyzed using bioinformatics software.Results:The phylogenetic trees showed that each gene fragment of the strain belonged to the Eurasian evolutionary branch, and the host source was of avian origin. The HA gene was closely related to the origin of the H3N6 virus. The NA gene was closely related to the H3N2 avian influenza virus from 2017 to 2020. The PB1 gene was closely related to the H5N6 avian influenza virus in Guangxi Zhuang Autonomous Region and Fujian Province from 2016 to 2022 and was not related to the PB1 gene of the H5N6 avian influenza epidemic strain in Guangzhou. The other internal gene fragments had complex sources with significant genetic diversity. Molecular characteristics indicated that the strain exhibited the molecular characteristics of a typical low pathogenic avian influenza virus and tended to bind to the receptors of avian origin. On important protein sites related to biological characteristics, this strain had mutations of PB2-L89V, PB1-L473V, NP-A184K, M1-N30D/T215A, and NS1-P42S/N205S.Conclusions:This study identified a novel reassortant H3N2 avian influenza virus by nanopore sequencing, with the PB1 gene derived from the H5N6 avian influenza virus. The virus had a low ability to spread across species, but further exploration was needed to determine whether its pathogenicity to the host was affected.

Objective To investigate the population density and seasonal fluctuations of Aedes albopictus in Guangzhou City, Guangdong Province, from 2021 to 2023, so as to provide insights into A. albopictus control and management of dengue fever. Methods The surveillance of A. albopictus density was performed in all surveillance sites assigned across all streets (townships) in Guangzhou City during the period from January to December from 2021 to 2023. The surveillance frequency was twice every half month from May to September, and once every month for the rest of a year. In each surveillance period, A. albopictus mosquito larvae were captured from indoor and outdoor small water containers in residential areas, parks, medical facilities, schools, other government sectors and social organizations, construction sites, special industries and others for mosquito species identification. Adult mosquitoes were captured using electric mosquito suction apparatus for species identification and gender classification. Adult mosquitoes and mosquito eggs were collected with mosquito and egg traps at the breeding and dwelling places of Aedes mosquitoes for identification. The mosquito oviposition index (MOI), Breteau index (BI), adult mosquito density index (ADI) and standard space index (SSI) were calculated. The A. albopictus density was classified into grades 0, 1, 2 and 3 in each surveillance site, with Grade 0 density defined eligible, and the eligible rate of A. albopictus density was calculated at all surveillance sites each year from 2021 to 2023. In addition, the changing trends in MOI, SSI, BI and ADI of A. albopictus were analyzed in Guangzhou City from 2021 to 2023. Results The eligible rates of A. albopictus density were 61.69%, 68.75% and 55.15% in surveillance sites of Guangzhou City from 2021 to 2023 (χ² = 297.712, P < 0.001), and appeared a tendency towards a reduction followed by a rise each year, which gradually reduced since January, maintained at a low level during the period between May and October, and gradually increased from November to December. The MOI, SSI, BI and ADI of A. albopictus all appeared a tendency towards a rise followed by a reduction in Guangzhou City during the period between January and December from 2021 to 2023. The BI of A. albopictus peaked in the first half of June in 2021 (4.03), the first half of July in 2022 (3.89) and the last half of August in 2023 (5.02), and the SSI of A. albopictus peaked in the last half of June in 2021 (0.93), the last half of May in 2022 (0.59), and the last half of June (0.94) and the first half of September in 2023 (1.12). In addition, the MOI of A. albopictus peaked in the first half of May in 2021 (8.64), the first half of June in 2022 (8.96), and the last half of May (10.21) and the last half of June in 2023 (10.89), and the ADI of A. albopictus peaked in the first half of June in 2021 (3.41), the last half of June in 2022 (4.06), and the first half of July in 2023 (3.61). Conclusions The density of A. albopictus is high in Guangzhou City during the period from May to October, and the risk of local outbreak caused by imported dengue fever is high. Persistent intensified surveillance of the density and seasonal fluctuation of A. albopictus is recommended and timely mosquito prevention and control is required according to the fluctuation in the A. albopictus density.