Influenza A(H1N1)pdm09 infection and viral load analysis in patients with different clinical presentations

BACKGROUND Influenza viral load (VL) can be a decisive factor in determining the antiviral efficacy in viral clearance. OBJECTIVE This study aimed to evaluate the rate of infection and the role of influenza VL on the clinical spectrum of illnesses among different patient groups attended at a tertiary hospital in Brazil. METHODS Samples were collected from patients presenting acute respiratory infection from 2009 to 2013. Overall, 2262 samples were analysed and distributed into three groups: (i) asymptomatic (AS); (ii) symptomatic outpatients (OP); and (iii) hospitalised patients (HP). VL (expressed in Log10 RNA copies/mL) was calculated through a quantitative real-time one-step reverse transcription-polymerase chain reaction (RT-PCR) assay aimed at the M gene, with human RNAseP target as internal control and normalising gene of threshold cycle values. FINDINGS A total of 162 (7.16%) H1N1pdm09 positive samples were analysed. Patients aged from 0.08 to 77 years old [median ± standard deviation (SD): 12.5 ± 20.54]. Children with 5 to 11 years old presented the highest detection (p < 0.0001). AS patients had the lowest VL, with a significant difference when compared with symptomatic patients (p = 0.0003). A higher VL was observed within two days of disease onset. Ten patients (HP group) received antiviral treatment and were followed up and presented a mean initial VL of 6.64 ± 1.82. A complete viral clearance for 50% of these patients was reached after 12 days of treatment. MAIN CONCLUSIONS It is important to evaluate AS patients as potential spreaders, as viral shedding was still present, even at lower VL. Our results suggest that patients with underlying diseases and severe clinical symptoms may be considered for prolonged viral treatment.

研究背景：流感病毒载量（influenza viral load, VL）是决定抗病毒治疗病毒清除疗效的关键因素。
研究目的：本研究旨在评估巴西某三级医院就诊的不同患者群体中，流感感染率以及病毒载量对疾病临床谱的影响。
研究方法：于2009年至2013年间收集急性呼吸道感染患者的样本。共计分析2262份样本，并将其分为三组：(i) 无症状感染者（AS）；(ii) 症状性门诊患者（OP）；(iii) 住院患者（HP）。采用针对M基因的定量实时一步法反转录聚合酶链反应（quantitative real-time one-step reverse transcription-polymerase chain reaction, RT-PCR）检测，以人RNAseP作为内参基因，通过阈值循环值完成归一化计算，得出病毒载量（以Log10 RNA拷贝数/mL表示）。
研究结果：共计分析162份H1N1pdm09阳性样本，患者年龄范围为0.08岁至77岁[中位数±标准差（SD）：12.5±20.54]。5至11岁儿童的病毒检出率最高（p < 0.0001）。无症状感染者的病毒载量最低，与有症状患者相比差异具有统计学意义（p = 0.0003）。发病后两天内可检测到更高的病毒载量。10名住院患者接受了抗病毒治疗并获得随访，其初始平均病毒载量为6.64±1.82。其中50%的患者在治疗12天后实现完全病毒清除。
主要结论：尽管无症状感染者的病毒载量较低，但仍存在病毒排毒现象，因此将其视为潜在传染源具有重要意义。本研究结果提示，合并基础疾病且临床症状严重的患者可考虑延长抗病毒治疗疗程。