Clinical, epidemiological, and genomic characteristics of a seasonal influenza A virus outbreak in Beijing: A descriptive study

Abstract

China experienced a severe influenza season that began at the end of February 2023. The aim of this post hoc analysis was to investigate the clinical, epidemiological, and genomic features of this outbreak in Beijing. The number of cases increased rapidly from the end of February and reached its peak in March, with 7262 confirmed cases included in this study. The median age was 33 years, and 50.3% of them were male. The average daily positive rate reached 69% during the peak period. The instantaneous reproduction number (Rt) showed a median of 2.1, exceeded 2.5 initially, and remaining above 1 for the following month. The most common symptoms were fever (75.0%), cough (51.0%), and expectoration (42.9%), with a median body temperature of 38.5°C (interquartile range 38–39). Eight clinical symptoms were more likely to be observed in cases with fever, with odds ratio greater than 1. Viral shedding time ranged from 3 to 25 days, with median of 7.5 days. The circulating viruses in Beijing mainly included H1N1pdm09 (clades 5a.2a and 5a.2a.1), following with H3N2 (clade 2a.2a.3a.1). The descriptive study suggests that influenza viruses in this influenza season had a higher transmissibility and longer shedding duration, with fever being the most common symptom.

Cocirculation and coinfection of multiple respiratory viruses during autumn and winter seasons of 2023 in Beijing, China: A retrospective study

“…After the relaxation of NPIs, studies 13–15 had reported that in mainland China, influenza activity recovered in 2021 compared with that in 2020 and intensified during the traditional influenza winter season. When China ended its “Zero‐COVID” policy on December 7, 2022, a sharp increase in influenza A activity in February 2023 combined with the spreading of Omicron posed huge a threat to the public healthcare system 11,12 . The present study reported a retrospective observation on the cocirculation of multiple respiratory viruses in Beijing in 2023.…”

“…When China ended its "Zero-COVID" policy on December 7, 2022, a sharp increase in influenza A activity in February 2023 combined with the spreading of Omicron posed huge a threat to the public healthcare system. 11,12 The present study reported a retrospective observation on the cocirculation of multiple respiratory viruses in Beijing in 2023.…”

“…8,9 Unlike most countries in the world that have adopted an open approach, China ended its "Zero-COVID" policy on December 7, 2022, and then the surging number of Omicron cases appeared in China, 10 together with a sharp increase in influenza incidence in February 2023. 11,12 Therefore, to better understand and prepare for the intricate dynamics of multiple respiratory viruses, the activity of respiratory pathogens during the spreading of Omicron and clinical characteristics of patients infected or coinfected with different respiratory pathogens needs investigation.…”

Genomic evolution of BA.5.2 and BF.7.14 derived lineages causing SARS-CoV-2 outbreak at the end of 2022 in China

“…The PANGO lineages of all genomes were determined according to the pangolin nomenclature. An in-house script was used to parse genomes with "N" and low coverage in order to identify the single nucleotide polymorphisms (SNPs) (21). The mutations in each genome were identified using Wuhan-Hu-1 as the reference.…”

Heterogeneity of influenza infection at precise scale in Yinchuan, Northwest China, 2012–2022: evidence from Joinpoint regression and spatiotemporal analysis

“…However, in the past decade, many regions worldwide have reported influenza outbreaks, such as Thailand 13 , Italy 14 , Taiwan 15 , and America 16 . Previous studies 17 – 20 on influenza largely focused on epidemiological characteristics and the analysis of influencing factors. In addition, Morabia 21 found that variation in social and healthcare-based determinants exacerbates influenza epidemics, and low socioeconomic status (SES) individuals are prone to bear the burden of infection.…”