2009甲型H1N1流感大流行期间北京儿童的流感监测

目的 了解2009年甲型H1N1流感大流行期间北京地区儿童中流感流行的情况.方法 采用WHO推荐的实时荧光定量RT-PCR和国家流感中心推荐的分型方法,对2009年甲型H1N1流感大流行期间因流感样症状来首都儿科研究所附属儿童医院就诊患儿的咽拭子标本进行流感病毒核酸检测.结果 2009年6月1日至2010年2月28日期间共检测了4363份咽拭子标本,其中623例为甲型H1N1阳性,阳性率为14.3%,657例为其他甲型流感病毒阳性(15.1%),所有甲型流感病毒的总阳性率为29.3%.623例中有23例为危重症病例(占阳性患者的3.7%),其中5例死亡.618例信息完整的甲型H1N1病例中,患儿年龄为14天～16岁,性别比例为男比女为1.3:1.1～3岁儿童占25.2%,3～6岁学龄前儿童和6～12岁学龄儿童所占比例相近,各约占30%.在监测期间,仅呈现了一个甲型H1N1的流行波.2009年11月达到最高峰,随后减弱,2010年2月快速下降至2.7%.对监测期间每周20～30份临床标本同时进行季节性流感的监测显示,季节性H3N2、甲型H1N1和乙型流感交替流行.呼吸道合胞病毒(RSV)在甲型H1N1流行趋势减缓后逐渐流行成为流行优势株.结论 2009年6月至2010年2月北京地区儿童中出现甲型H1N1的流行,主要累及学龄前和学龄儿童.季节性流感和RSV与甲型H1N1交替流行.     

季节性流感与甲型H1N1流感

流行性感冒（流感）是由流感病毒引起的急性呼吸道传染病。流感病毒传染性强,传播速度快。主要通过呼吸道传播,接触患者的呼吸道分泌物、体液和被污染的物品也可造成传播。     

2013~2018年天津市津南区0~14岁儿童季节性 甲型H1N1流感病原学监测分析

目的 分析2013~2018年天津市津南区季节性甲型H1N1流感流行情况,为科学预防和控制流感提供依据。方法 选择咸水沽医院作为监测哨点医院,采集2013年4月1日~2018年3月31日0~14岁儿童流感样病例（ILI）的咽拭子标本,采用实时荧光定量RT-PCR方法检测季节性甲型H1N1流感病毒核酸,以每年4月1日至次年3月31日为监测周期进行统计分析。结果 5个监测周期采集ILI 咽拭子标本分别为588、601、609、591和583份,季节性甲型H1N1流感病毒阳性率分别为9.69%、0、7.39%、10.15%和12.35%,阳性率比较,差异有统计学意义（P＜0.05）。5 个监测周期中有4个季节性甲型H1N1流感流行期,分别为2013年12月~2014年1月、2016年1~3月、2017年2~3月和2018年1~2月,2014年3月~2015年12月阳性病例数为0。按照年龄分为0~2岁、3~5岁、6~8岁、9~11岁和12~14岁5个年龄组,阳性率分别为3.15%、9.98%、11.08%、8.52%和5.98%,各年龄组之间阳性率比较,差异无统计学意义（P＞0.05）。不同性别人群的季节性甲型H1N1流感阳性率差异无统计学意义（P＞0.05）。结论 季节性甲型H1N1流感病毒呈现出季节性流行的特点,流行期一般在冬春季,高峰期出现在1月份左右,3~8岁年龄儿童阳性病例数量最多,为易感人群。为更好防控流感,及时掌握流行趋势,仍需加强监测。     

我国首起甲型H1N1流感本地感染疫情感染环境的调查

目的了解引起我国首起甲型H1N1流感本地感染病例感染的环境危险因素。方法对感染的环境进行实地现场勘察。结果感染的环境主要为通风换气不良,无新风补给,为一个相对密闭的环境。结论与传染源在同一个相对密闭、空气流通不畅的环境内密切接触是引起此起甲型H1N1流感本地感染疫情的主要原因。公共场所的通风设施不健全应纳入公共场所管理的卫生问题范围中,并应引起卫生监管部门重视。     

一起甲型H1N1流感暴发的流行病学调查分析

目的分析一起甲型H1N1流感爆发疫情的原因和特点。方法对疫情进行描述性统计分析,探讨本次爆发的流行因素。结果这是一起甲型H1N1流感爆发疫情,8月22日至29日该厂共发生病例69例,总罹患率为10.5%,年龄18～30岁,平均21岁,男女比例为1：1.02,男女罹患率差异无统计学意义,病例宿舍分布较分散,住宿员工和外租员工罹患率差异无统计学意义。白班人群罹患率为15.6%,晚班人群罹患率为4.7%,白班人群发病率明显高于夜班人群,差异具有统计学意义。病例主要集中在白班冲压课,罹患率为26.2%,而白班清洗课罹患率仅为7.6%,两者差异有统计学意义。晚班冲压课和清洗课罹患率差异无统计学意义。冲压1线、冲压5线白班的发病率较高,分别为27.6%和26.3%,冲压线白班的病例有明显的空间聚集性。经实验室检测有4份甲型H1N1流感阳性。结论本次爆发最重要的传播途径是近距离的飞沫传播以及通过流水线的接触传播,采取以隔离传染源为核心的综合措施,对彻底控制疫情起到了决定性作用。     

应用SEIR模型预测2009年甲型H1N1流感流行趋势

目的 探讨SEIR模型预测甲型H1N1流感流行趋势的功效.方法 利用国庆前北京市流感样病例数、流感样病例中甲型H1N1流感阳性率及二级以上医院流感样病例就诊率等参数估算甲型H1N1流感实际感染人数,基于传染病传播动力学,建立SEIR模型,对国庆后甲型H1N1流感的流行趋势及高峰达到时间进行预测,与甲型H1N1流感病原学...     

甲型H1N1流感双重荧光PCR快速筛查方法的研究

目的优化一种甲型H1N1流感的双重荧光PCR快速筛查方法。方法根据WHO推荐的甲型H1N1流感检测方案合成、标记引物和探针。通过改进反应条件与参数．优化了甲型H1N1流感的双重荧光PCR检测方法。结果该方法敏感度高,特异性强,重复性好。应用该方法检测患者实际样品,结果与WHO推荐方法的检测结果一致;应用该法可在4h内完成对样品中甲型H1N1流感的检验。结论本研究优化的甲型H1N1流感的双重荧光PCR快速筛查方法可用于甲型H1N1流感的诊断。     

广东省2009年甲型H1N1流感流行与网络搜索情况的相关性分析

目的分析互联网中文搜索词搜索情况和广东省甲型H1N1流感活动情况的相关性,探索网络搜索数据在流感等疾病监测中的应用。方法利用流感监测系统和互联网搜索引擎,回顾性搜集2009年H1N1流感监测数据和网络搜索数据,并采用描述性统计和Pearson相关分析方法进行数据分析。结果广东省全年甲型H1N1流感活动在第48周达到高峰,流感监测数据和＂甲流＂网络搜索情况呈正相关（r=0.914,P〈0.001）。结论与流感有关的网络搜索情况较好地反映了流感活动水平,网络搜索数据可作为辅助流感等传染病监测的数据源。     

基于空间自相关分析的北京市甲型H1N1流感流行特征研究

目的 探讨2009年北京市甲型H1N1流感发病的地理区域相关性和聚集性,为今后传染病发病的空间自相关性分析提供参考依据.方法 利用OpenGeoDa 1.0.1软件进行空间全局和局部自相关性分析,呈现2009年甲型H1N1流感空间聚集区域.结果 2009年北京市甲型H1N1流感发病分布不是随机的,呈现显著的空间聚集,即...     

2009—2010年广州甲型H1N1流感的流行特征分析

目的分析甲型H1N1流感在广州的流行特征。方法 2009年5月至2010年4月,每周分别从广州四家监测医院采集流感样症状患者的嗽口液或咽拭子,采用real-time PCR方法鉴定甲型H1N1流感病毒;在广州5大城区采集不同年龄的人群血清,通过血凝抑制实验检测血清中甲型H1N1流感抗体;对其时间和年龄的分层进行分析。结果全年共采集嗽口液或咽拭子3580份,甲型H1N1流感核酸检测阳性530份,阳性率为14.8%,阳性率最高的月份出现在10～12月,为36.5%～42.3%,阳性率最高的年龄组为5～岁和15～岁组,为18.5%和24.2%,最低的年龄组为≥60岁组,为4.1%。人群血清标本共采集1527份,甲型H1N1流感抗体阳性439份,阳性率为28.7%,阳性率最高的年龄组为5～岁和15～岁组,为36.1%和39.5%,最低的年龄组为≥60岁组,为8.6%。结论甲型H1N1流感的流行期发生在10～12月,流行时间短,感染的主要人群是学龄组人群,而老年人群的感染率相对较低。预防流感的工作重点应放在学校内。     

Classical swine H1N1 influenza viruses confer cross protection from swine-origin 2009 pandemic H1N1 influenza virus infection in mice and ferrets

The hemagglutinin of the 2009 pandemic H1N1 influenza virus is a derivative of and is antigenically related to classical swine but not to seasonal human H1N1 viruses. We compared the A/California/7/2009 (CA/7/09) virus recommended by the WHO as the reference virus for vaccine development, with two classical swine influenza viruses A/swine/Iowa/31 (sw/IA/31) and A/New Jersey/8/1976 (NJ/76) to establish the extent of immunologic cross-reactivity and cross-protection in animal models. Primary infection with 2009 pandemic or NJ/76 viruses elicited antibodies against the CA/7/09 virus and provided complete protection from challenge with this virus in ferrets; the response in mice was variable and conferred partial protection. Although ferrets infected with sw/IA/31 virus developed low titers of cross-neutralizing antibody, they were protected from pulmonary replication of the CA/7/09 virus. The data suggest that prior exposure to antigenically related H1N1 viruses of swine-origin provide some protective immunity against the 2009 pandemic H1N1 virus.     

Duration of viral shedding in patients admitted to hospital with pandemic influenza A/H1N1 2009 infection

Little is known about the kinetics of viral shedding of pandemic influenza A/H1N1 2009 virus. Influenza RNA, as a surrogate for viral clearance, was therefore measured on days 1, 5, 7, and 10 or more in patients admitted to hospital with pandemic influenza A/H1N1 2009 infection. A total of 72 patients who were admitted to hospital with confirmed pandemic influenza A/H1N1 2009 at a tertiary care hospital, Seoul, South Korea, between 1 September and 11 November 2009 were evaluated. The median duration of viral shedding, as assessed by RT-PCR, was 9 days, as determined by the Kaplan-Meier method. Patients who were positive by RT-PCR at their last assay, but who were discharged before the next RT-PCR test due to symptom improvement, were censored from the analysis. If such patients were included, with the assumption that they had negative viral status at discharge, the median duration of viral shedding was 5 days (interquartile range, 2-8 days). These calculations thus suggest that the true median duration of viral shedding is between 5 and 9 days. Univariate analysis showed that delayed administration of antiviral therapy and comorbidity were associated with slower viral clearance. Multivariate analysis showed that oseltamivir started after the first day of symptoms (OR 2.7, 95% CI 1.2-5.7) was associated independently with slower viral clearance. These findings indicate that, in about 50% of patients admitted to hospital with pandemic influenza A/H1N1 2009, virus can be positive as tested by RT-PCR on the eighth day after developing symptoms of influenza. The present findings also indicate that starting antiviral therapy within 24 hr of the onset of symptoms is associated with more rapid viral clearance.     

Genetic analysis of HA gene of pandemic H1N1 2009 influenza viruses circulating in India

The H1N1 2009 influenza pandemic took the health care workers by surprise in spite of warning about influenza pandemic. Influenza A virus has the ability to overcome immunity from previous infections through the acquisition of genetic changes by shift or drift. Thus, understanding the evolution of the viruses in human is important for the surveillance and the selection of vaccine strains. A total of 23 pandemic A/H1N1 2009 viral HA gene sequences were downloaded from NCBI submitted during March and May 2010 by NIV and were analysed. Along with that the vaccine strain A/California/07/2009 was also downloaded from NCBI. All the sequences were used to analyse the evolution of the haemagglutinin (HA) by phylogenetic analysis. The HA gene could be divided into four groups with shift from 1 to lV revealing that the HA genes of the influenza A viruses evolved in a sequential way, in comparison to vaccine strain A/California/07/2009. Amino acid sequence analysis of the HA genes of the A/H1N1 2009 isolates, revealed mutations at positions 100, 220 and additional mutations in different positions 114, 171, 179, 190, 208, 219, 222, 239, 240, 247, 251, 260 and 285 .The mutations identified showed the adaptation of the new virus to the host that could lead to genetic changes inherent to the virus resulting in a reassortant which could be catastrophic, hence continuous monitoring of strains is mandatory.     

Lymphocytopenia as a marker for pandemic influenza A/H1N1 2009 virus infection in children

Lymphocytopenia has been reported in adults with pandemic influenza A/H1N1 2009 infection, but data in children are inconclusive. Data from 76 children presented with flu‐like symptoms between July and November 2009 and tested for pandemic influenza A/H1N1 2009 virus and white blood cell (WBC) counts were analyzed. Samples from 37 (48.7%) children resulted in a positive PCR assay for pandemic influenza A/H1N1 2009 virus. When comparing data from these children with data from 39 (51.3%) children with uncomplicated flu‐like illness and negative PCR assay for pandemic influenza A/H1N1 2009 virus, no difference in disease duration, median age, red blood cell count, hemoglobin concentration, C reactive protein concentration, and absolute neutrophil count was observed, whereas significant differences were apparent when considering WBC count, relative and absolute lymphocyte count, absolute lymphocyte count z‐score, and platelet count. Receiver operating characteristic curve analysis revealed that the best absolute lymphocyte count and absolute lymphocyte count z‐score cut‐points that simultaneously maximized sensitivity and specificity were 2,256 cells/µl and ?0.89, respectively, sensitivity being 0.81 (95% CI: 0.68–0.94), specificity 0.87 (95% CI: 0.77–0.98), positive predictive value 0.85 (95% CI: 0.74–0.97), and negative predictive value 0.83 (95% CI: 0.71–0.94). In conclusion, lymphocytopenia is a marker for influenza A/H1N1 2009 virus infection in children. Absolute lymphocyte count <2,556 cells/µl or absolute lymphocyte count z‐score < ?0.89 may be useful cut‐offs to discriminate against children at higher risk of infection during epidemics. Considering that the pandemic virus is highly likely to continue to circulate in the coming winter season, these findings provide direct and practical implications for the near future. J. Med. Virol. 83:1–4, 2011. © 2010 Wiley‐Liss, Inc.     

Pathologic study of pandemic influenza A (H1N1) 2009 cases from India

The pandemic influenza A (H1N1) 2009 originated in Mexico and rapidly spread to the United States and many other countries. India reported the first pandemic influenza case in May 2009. Autopsy studies describing the pathology of pandemic influenza infection in humans have appeared in the literature and most of these were from Western countries. We present the clinicopathologic features in 46 fatal cases with confirmed pandemic influenza A (H1N1) 2009 virus infection during August 2009 to October 2010. Postmortem needle biopsy tissues were examined for histopathological changes and distribution of virus antigen by immunohistochemistry. The results are comparable with previous autopsy studies. Diffuse alveolar damage was the consistent finding in the lung tissues. However, underlying medical conditions were not noted in the cases from present study. Consistent presence of viral antigen was noted in the bronchiolar epithelium without any reference to the duration of illness. This study also emphasizes the use of the postmortem needle biopsy technique whenever an autopsy is not possible.     

Differential diagnosis of pandemic (H1N1) 2009 infection by detection of haemagglutinin with an enzyme-linked immunoassay

A sensitive and convenient immunoassay that can directly differentiate pandemic (H1N1) 2009 (pH1N1) virus from seasonal influenza virus can play an important role in the clinic. In the presented study, a double-sandwich ELISA (pH1N1 ELISA), based on two monoclonal antibodies against haemagglutinin (HA) of the pH1N1 virus, was developed. After laboratory determination of the sensitivity and specificity characteristics, the performance of this assay was evaluated in a cohort of 904 patients with influenza-like illness. All seven strains of pH1N1 virus tested were positive by pH1N1 ELISA, with an average lower detection limit of 10^{3.0 ± 0.4} tissue culture infective dose (TCID)₅₀/mL (or 0.009 ± 0.005 HA titre). Cross-reaction of the assay with seasonal influenza virus and other common respiratory pathogens was rare. In pH1N1-infected patients, the sensitivity of the pH1N1 ELISA was 92.3% (84/91, 95% CI 84.8–96.9%), which is significantly higher than that of the BD Directigen EZ Flu A + B test (70.3%, p <0.01). The specificity of pH1N1 ELISA in seasonal influenza A patients was 100.0% (171/171, 95% CI 97.9–100.0%), similar to that in non-influenza A patients (640/642, 99.7%, 95% CI 98.9–100.0%). The positive predictive value for pH1N1 ELISA was 97.7% and the negative predictive value was 99.1% in this study population with a pH1N1 prevalence of 10.1%. In conclusion, detection of HA of pH1N1 virus by immunoassay appears to be a convenient and reliable method for the differential diagnosis of pH1N1 from other respiratory pathogens, including seasonal influenza virus.