The emergence of influenza B as a major respiratory pathogen in the absence of COVID-19 during the 2021–2022 flu season in China

• Published in: Virology journal 2023-08, Vol.20 (1), p.1-189, Article 189
• Main Authors: Chang, De, Lin, Mingui, Song, Ning, Zhu, Zhantao, Gao, Jing, Li, Shujun, Liu, Hongmei, Liu, DeZhi, Zhang, Yu, Sun, Wenkui, Zhou, Xuan, Yang, Bin, Li, Yongjun, Wang, Lili, Xiao, Zhiqing, Li, Kailong, Xing, Lihua, Xie, Lixin, Sharma, Lokesh
• Format: Article
• Language: English
• Subjects: Cell death; Consent; COVID-19; COVID-19 diagnostic tests; Data collection; Disease control; Distribution; Electronic health records; Fever; Fungal infections; Genomes; Hospitalization; Hospitals; Identification and classification; Influenza; Influenza A; Influenza B; Influenza viruses; Kinases; Medical laboratories; Medical records; Morbidity; Mortality; Pathogens; Patients; Pneumonia; Respiratory tract infection; Respiratory tract infections; Risk factors; Vaccination; Viral infections
• ISSN: 1743-422X; 1743-422X
• DOI: 10.1186/s12985-023-02115-x

The emergence of COVID-19 and the implementation of preventive measures and behavioral changes have led to a significant decrease in the prevalence of other respiratory viruses. However, the manner in which seasonal viruses will reemerge in the absence of COVID-19-related restrictions remains unknown. Starting from October 2021, a substantial increase in the number of patients visiting the designated fever clinics in Beijing was observed, with this trend continuing until January 2022. COVID-19 tests conducted on these patients yielded negative results, while the positivity rate for influenza rose from approximately 8% in October 2021 to over 40% by late January 2022. The cases started to decline after this peak. Data from China CDC confirmed that influenza B is a major pathogen during the season. Sequencing of the viral strain revealed the presence of the Victoria-like lineage of the influenza B strain, with minor variations from the Florida/39/2018 strain. Analysis of the hospitalized patients' characteristics indicated that severe cases were relatively more prevalent among younger individuals, with an average age of 40.9 [+ or -] 24.1 years. Among the seven patients who succumbed to influenza, the average age was 30 [+ or -] 30.1 years. These patients exhibited secondary infections involving either bacterial or fungal pathogens and displayed elevated levels of cell death markers (such as LDH) and coagulation pathway markers (D-dimer). Influenza B represents a significant infection threat and can lead to substantial morbidity and mortality, particularly among young patients. To mitigate morbidity and mortality rates, it is imperative to implement appropriate vaccination and other preventive strategies.