Department of Clinical Virology, Christian Medical College, Vellore, Tamil Nadu, India.
PLoS One. 2012;7(9):e41507. doi: 10.1371/journal.pone.0041507. Epub 2012 Sep 5.
The burden of the pandemic (H1N1) 2009 influenza might be underestimated if detection of the virus is mandated to diagnose infection. Using an alternate approach, we propose that a much higher pandemic burden was experienced in our institution.
METHODOLOGY/PRINCIPAL FINDINGS: Consecutive patients (n = 2588) presenting to our hospital with influenza like illness (ILI) or severe acute respiratory infection (SARI) during a 1-year period (May 2009-April 2010) were prospectively recruited and tested for influenza A by real-time RT-PCR. Analysis of weekly trends showed an 11-fold increase in patients presenting with ILI/SARI during the peak pandemic period when compared with the pre-pandemic period and a significant (P<0.001) increase in SARI admissions during the pandemic period (30 ± 15.9 admissions/week) when compared with pre-pandemic (7 ± 2.5) and post-pandemic periods (5 ± 3.8). However, Influenza A was detected in less than one-third of patients with ILI/SARI [699 (27.0%)]; a majority of these (557/699, 79.7%) were Pandemic (H1N1)2009 virus [A/H1N1/09]. An A/H1N1/09 positive test was correlated with shorter symptom duration prior to presentation (p = 0.03). More ILI cases tested positive for A/H1N1/09 when compared with SARI (27.4% vs. 14.6%, P = 0.037). When the entire study population was considered, A/H1N1/09 positivity was associated with lower risk of hospitalization (p<0.0001) and ICU admission (p = 0.013) suggesting mild self-limiting illness in a majority.
CONCLUSION/SIGNIFICANCE: Analysis of weekly trends of ILI/SARI suggest a higher burden of the pandemic attributable to A/H1N1/09 than estimates assessed by a positive PCR test alone. The study highlights methodological consideration in the estimation of burden of pandemic influenza in developing countries using hospital-based data that may help assess the impact of future outbreaks of respiratory illnesses.
如果检测病毒是诊断感染的必需手段，那么大流行性流感（H1N1）2009 的负担可能被低估。我们采用替代方法，提出在我们的机构中经历了更高的大流行负担。
方法/主要发现：在为期一年的时间内（2009 年 5 月至 2010 年 4 月），连续有流感样疾病（ILI）或严重急性呼吸道感染（SARI）的患者（n = 2588）前瞻性地招募到我们的医院进行检测。对每周趋势的分析表明，与大流行前时期相比，ILI/SARI 患者在大流行高峰期增加了 11 倍，而在大流行期间 SARI 入院人数显著增加（30 ± 15.9 人/周）与大流行前（7 ± 2.5）和大流行后（5 ± 3.8）相比。然而，ILI/SARI 患者中仅不到三分之一（699 例[27.0％]）检测到流感 A，其中大多数（557/699，79.7％）为大流行性（H1N1）2009 病毒[A/H1N1/09]。A/H1N1/09 阳性检测结果与就诊前症状持续时间较短相关（p = 0.03）。与 SARI 相比，ILI 病例中 A/H1N1/09 的阳性检出率更高（27.4％比 14.6％，p = 0.037）。当考虑整个研究人群时，A/H1N1/09 阳性与住院风险降低相关（p<0.0001）和 ICU 入院风险降低（p = 0.013），表明大多数患者患有轻度自限性疾病。
结论/意义：ILI/SARI 的每周趋势分析表明，归因于 A/H1N1/09 的大流行负担高于单独通过 PCR 检测阳性估计的负担。该研究强调了在使用基于医院的数据评估发展中国家大流行性流感负担时的方法学考虑因素，这可能有助于评估未来呼吸道疾病暴发的影响。
