National Influenza Centre, Royal Centre for Disease Control, Ministry of Health, Thimphu, Bhutan.
Department of Virology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand.
PLoS One. 2024 Sep 17;19(9):e0304849. doi: 10.1371/journal.pone.0304849. eCollection 2024.
Influenza (Flu) causes considerable morbidity and mortality globally, and in Bhutan, Flu viruses are a leading cause of acute respiratory infection and cause outbreaks during Flu seasons. In this study, we aim to analyze the epidemiology and the genetic characterization of Flu viruses circulated in Bhutan in 2022.
Respiratory specimens were collected from patients who meet the case definition for influenza-like illness (ILI) and severe acute respiratory infection (SARI) from sentinel sites. Specimens were tested for Flu and SARS-CoV-2 viruses by RT-PCR using the Multiplex Assay. Selected positive specimens were utilized for Flu viral genome sequencing by next-generation sequencing. Descriptive analysis was performed on patient demographics to see the proportion of Flu-associated ILI and SARI. All data were analyzed using Epi Info7 and QGIS 3.16 software.
A weekly average of 16.2 ILI cases per 1000 outpatient visits and 18 SARI cases per 1000 admitted cases were reported in 2022. The median age among ILI was 12 years (IQR: 5-28) and SARI was 6.2 (IQR: 2.5-15) years. Flu A(H3N2) (70.2%) subtype was the most predominant circulating strain. Flu A(H1N1)pdm09 and Flu B viruses belonged to subclades that were mismatched to the vaccine strains recommended for the 2021-2022 season but matched the vaccine strain for the 2022-2023 season with vaccine efficacy 85.14% and 88.07% respectively. Flu A(H3N2) virus belonged to two subclades which differed from the vaccine strains recommended in both the 2021-2022 and 2022-2023 seasons with vaccine efficacy 68.28%.
Flu virus positivity rates were substantially elevated during the Flu season in 2022 compared to 2021. Flu A(H3N2) subtype was the most predominant circulating strain in the country and globally. Genetic characterization of the Flu viruses in Bhutan showed a close relatedness of high vaccine efficacy with the vaccine strain that WHO recommended for the 2022-23 season.
流感（Flu）在全球范围内导致了相当大的发病率和死亡率，在不丹，流感病毒是急性呼吸道感染的主要原因，并在流感季节引起疫情。在这项研究中，我们旨在分析 2022 年不丹流行的流感病毒的流行病学和遗传特征。
从符合流感样疾病（ILI）和严重急性呼吸道感染（SARI）病例定义的哨点患者中采集呼吸道标本。使用多重检测 RT-PCR 法检测 Flu 和 SARS-CoV-2 病毒。选择阳性标本进行下一代测序的流感病毒基因组测序。对患者人口统计学数据进行描述性分析，以了解流感相关 ILI 和 SARI 的比例。所有数据均使用 Epi Info7 和 QGIS 3.16 软件进行分析。
2022 年，每周平均每 1000 次门诊就诊有 16.2 例 ILI 病例，每 1000 例住院患者中有 18 例 SARI 病例。ILI 的中位数年龄为 12 岁（IQR：5-28），SARI 为 6.2 岁（IQR：2.5-15）。流感 A(H3N2)（70.2%）亚系是最主要的流行株。流感 A(H1N1)pdm09 和 Flu B 病毒属于与 2021-2022 年季节推荐疫苗株不匹配但与 2022-2023 年季节疫苗株匹配的亚系，疫苗效力分别为 85.14%和 88.07%。流感 A(H3N2)病毒属于两个亚系，与 2021-2022 年和 2022-2023 年季节推荐的疫苗株均不同，疫苗效力为 68.28%。
与 2021 年相比，2022 年流感季节的流感病毒阳性率显著升高。流感 A(H3N2) 亚系是该国和全球最主要的流行株。不丹流感病毒的遗传特征表明，与世界卫生组织推荐的 2022-2023 年季节疫苗株具有高度相关的高疫苗效力。
