儿童甲型H1N1流感和季节性流感患者的病毒载量及相关临床症状研究

目的 分析并比较儿童甲型H1N1流感和季节性流感患者咽拭子标本的病毒载量及相关临床症状.方法 应用荧光PCR方法对采集的咽拭子标本进行检测,并通过建立核酸标准品,绘制标准曲线,测定标本中的病毒载量,同时结合所收集的患者临床症状数据资料应用随机区组方差和卡方检验方法进行统计分析.结果 2009年9月至2010年9月期间收集的1,040份咽拭子标本中,共检出甲型H1N1流感病毒阳性标本120份,甲型H3N2流感病毒阳性标本61份,乙型流感病毒阳性标本99份;对收集的流感阳性标本病毒载量测定结果显示:不同型别,不同发病时间流感患者咽拭子标本的病毒载量差异无统计学意义(P＞0.05);甲型H1N1流感、季节性流感感染者的性别比例差异无统计学意义,甲型H1N1流感感染者出现咳嗽,流涕临床症状者明显高于与乙型流感感染者.结论 甲型H1N1流感患者咳嗽,流涕症状比季节性乙型流感患者多见,而甲型H1N1流感和季节性流感患者咽拭子标本的病毒载量无显著性差异.     

Pediatric hospital admissions from influenza A (H1N1) in Brazil: effects of the 2010 vaccination campaign

In 2009, the influenza A (H1N1) virus spread rapidly around the world, causing the first pandemic of the 21^st Century. In 2010, there was a vaccination campaign against this new virus subtype to reduce the morbidity and mortality of the disease in some countries, including Brazil. Herein, we describe the clinical and epidemiological characteristics of patients under 19 years of age who were hospitalized with confirmed influenza A (H1N1) infection in 2009 and 2010. We retrospectively reviewed files from the pediatric patients who were admitted to a university hospital with real-time polymerase chain reaction (RT-PCR) confirmed influenza A (H1N1) infection in 2009 and 2010. There were 37 hospitalized patients with influenza A (H1N1) in 2009 and 2 in 2010. In 2009, many of the hospitalized children had an underlying chronic disease and a lower median age than those not hospitalized. Of the hospitalized patients, 78% had a chronic disease, primarily pneumopathy (48%). The main signs and symptoms of influenza were fever (97%), cough (76%), and dyspnea (59%). Complications occurred in 81% of the patients. The median length of hospitalization was five days; 27% of the patients required intensive care, and two died. In 2010, two patients were hospitalized with influenza A (H1N1): one infant with adenovirus co-infection who had received one previous H1N1 vaccine dose and presented with respiratory sequelae and a 2-month-old infant who had a hospital-acquired infection. An impressive reduction in hospital admissions was observed in 2010 when the vaccination campaign took place in Brazil.     

Characterization of 2009 pandemic influenza A (H1N1) virus specimens with a positive hemagglutinin 1 signal in the Luminex xTAG respiratory viral panel assay

This retrospective review analyzed Luminex xTAG respiratory viral panel (RVP) results for 2009 pandemic influenza A (H1N1) virus specimens. Comparing median fluorescence intensity (MFI) signals for the influenza A virus and hemagglutinin 1 (H1) reactions for specimens with very low positive (MFI < 1,000) or "no-call" H1 results reliably distinguished 2009 H1N1 from seasonal virus.     

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.     

Antiviral potential of exogenous human omega interferon to inhibit pandemic 2009 A (H1N1) influenza virus

The pandemic 2009 H1N1 influenza virus broke out in North America and spread rapidly throughout the world. The type I interferon (IFN) response represents one of the first lines of defense against influenza virus infections. In this study, the protective potential of human exogenous IFN-ω against pandemic 2009 A (H1N1) influenza virus was assessed both in vitro and in guinea pigs. The viral loads of pandemic 2009 A (H1N1) influenza virus strains A/California/04/2009 and A/Beijing/501/2009 were reduced by up to 5000-fold in Caco-2 cells by the addition of human IFN-ω. With daily intranasal treatment with human IFN-ω the viral load of pandemic 2009 A (H1N1) influenza virus strain A/California/04/2009 decreased by 1000-fold in lung tissues of guinea pigs. These results provide strong support for the application of human IFN-ω pretreatment to human influenza control.     

The pathogenesis of influenza virus infections: the contributions of virus and host factors

Influenza viruses cause acute respiratory inflammation in humans and symptoms such as high fever, body aches, and fatigue. Usually these symptoms improve after several days; however, the 2009 pandemic H1N1 influenza virus [influenza A(H1N1) 2009] is more pathogenic than seasonal influenza viruses and the pathogenicity of highly pathogenic H5N1 viruses is still higher. The 1918 influenza pandemic virus caused severe pneumonia, resulting in an estimated 50 million deaths worldwide. Several virulence factors have been identified in these virus strains, but host factors are also responsible for the pathogenesis of infections caused by virulent viruses. Here, we review the contributions of both virus and host factors to the pathogenesis of these viral infections.     

Induction of inflammatory cytokines and toll-like receptors in human normal respiratory epithelial cells infected with seasonal H1N1, 2009 pandemic H1N1, seasonal H3N2, and highly pathogenic H5N1 influenza virus

Respiratory epithelial cells are one of main targets for infections caused by influenza viruses. Recently, the induction of proinflammatory cytokines and toll-like receptors (TLRs) in normal human bronchial/tracheal epithelial cells infected with seasonal H1N1, 2009 pandemic H1N1, seasonal H3N2, or highly pathogenic H5N1 influenza virus were studied to understand the pathogenesis and early immune responses. The cells were productively infected with the viruses. Among the inflammatory cytokines tested, interleukin (IL)-8 was predominantly induced in virus-infected cells. Among the chemokines tested, interferon-γ-inducible protein-10 (IP-10) and growth-related oncogene-α (GRO-α) were predominantly induced in virus-infected cells. TLR-5 was predominantly induced in cells infected with seasonal H1N1, pandemic H1N1, or H5N1 influenza virus, and TLR-3 was predominantly induced in cells infected with seasonal H3N2 influenza virus. Taken together, the results suggest that IL-8, IP-10, and GRO-α are predominantly induced in respiratory epithelial cells infected with influenza A viruses, and that TLR-5 and TLR-3 are involved in the stimulation of virus-infected respiratory epithelial cells.     

The validation of a real-time RT-PCR assay which detects influenza A and types simultaneously for influenza A H1N1 (2009) and oseltamivir-resistant (H275Y) influenza A H1N1 (2009)

Influenza A H1N1 (2009) was declared by the World Health Organisation (WHO) as the first influenza pandemic of the 21st century. Rapid detection of influenza A and differentiation of influenza A H1N1 (2009) and seasonal influenza A is beneficial. In addition the rapid detection of antiviral resistant strains of influenza A H1N1 (2009) would be useful for clinicians to allow for change to an effective treatment at a much earlier stage if resistance is found. It was the aim of this study to develop a real-time RT-PCR that can detect all influenza A viruses and type simultaneously for influenza A H1N1 (2009) and oseltamivir resistant (H275Y) influenza A H1N1 (2009). This multiplex assay will allow laboratories to screen respiratory samples for all types of influenza A, influenza A H1N1 (2009) virus and oseltamivir resistant (H275Y) influenza A H1N1 (2009) virus in a rapid and cost effective format, ensuring that typing methods for seasonal and avian viruses are used on a smaller subset of samples. Since most virology laboratories already offer a molecular service for influenza A this assay could easily be implemented into most areas at little cost therefore increasing local access to resistance testing.     

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.     

Viral aetiology of influenza-like illness in Belgium during the influenza A(H1N1)2009 pandemic

The purpose of this investigation was to determine the proportion of influenza-like illness (ILI) attributable to specific viruses during the influenza A(H1N1)2009 pandemic and to describe the demographic and clinical characteristics of ILI due to respiratory viruses in Belgium. Nasopharyngeal swabs were collected from ILI patients by general practitioners (GPs) and paediatricians (PediSurv) and analysed for viruses. Of 139 samples collected from children <5 years of age by PediSurv, 86 were positive, including 28 influenza (20%), 27 respiratory syncytial virus (RSV) (19%), 21 rhinovirus (17%), 12 human metapneumovirus (hMPV) (9%) and ten parainfluenza virus (PIV) (7%). Of 810 samples received from GPs, 426 were influenza (53%). Of 312 influenza-negative samples, 41 were rhinovirus (13%), 13 RSV (4%), 11 PIV (4%) and three hMPV (1%). Influenza mostly affected the 6-15 years old age group. Other respiratory viruses were commonly detected in the youngest patients. Similar clinical symptoms were associated with different respiratory viruses. Influenza A(H1N1)2009 was the most detected virus in ILI patients during the 2009-2010 winter, suggesting a good correlation between ILI case definition and influenza diagnosis. However, in children under 5 years of age, other respiratory viruses such as RSV were frequently diagnosed. Furthermore, our findings do not suggest that the early occurrence of the influenza A(H1N1)2009 epidemic impacted the RSV epidemic in Belgium.     

Changes in epidemiology,clinical features and severity of influenza A (H1N1) 2009 pneumonia in the first post-pandemic influenza season

Although the influenza A (H1N1) 2009 virus is expected to circulate as a seasonal virus for some years after the pandemic period, its behaviour cannot be predicted. We analysed a prospective cohort study of hospitalized adults with influenza A (H1N1) 2009 pneumonia at 14 teaching hospitals in Spain to compare the epidemiology, clinical features and outcomes of influenza A (H1N1) 2009 pneumonia between the pandemic period and the first post-pandemic influenza season. A total of 348 patients were included: 234 during the pandemic period and 114 during the first post-pandemic influenza season. Patients during the post-pandemic period were older and more likely to have chronic obstructive pulmonary disease, chronic kidney disease and cancer than the others. Septic shock, altered mental status and respiratory failure on arrival at hospital were significantly more common during the post-pandemic period. Time from illness onset to receipt of antiviral therapy was also longer during this period. Early antiviral therapy was less frequently administered to patients during the post-pandemic period (22.9% versus 10.9%; p 0.009). In addition, length of stay was longer, and need for mechanical ventilation and intensive-care unit admission were significantly higher during the post-pandemic period. In-hospital mortality (5.1% versus 21.2%; p <0.001) was also greater during this period. In conclusion, significant epidemiological changes and an increased severity of influenza A (H1N1) 2009 pneumonia were found in the first post-pandemic influenza season. Physicians should consider influenza A (H1N1) 2009 when selecting microbiological testing and treatment in patients with pneumonia in the upcoming influenza season.     

Influenza virus infections from 0 to 2 years of age: A birth cohort study

Background/purposeInfluenza vaccine has been recommended in Finland since 2007 for all children of 6–35 months of age and in 2009 for those ≥6 months against pandemic influenza. We investigated the incidence of influenza and vaccine effectiveness in a birth cohort of children in 2008–2011.MethodsWe followed 923 children from birth to 2 years of age for respiratory tract infections. A nasal swab sample for PCR for influenza A and B viruses was taken at the onset of acute respiratory infections. Samples were collected either at the study clinic or at home by parents. Vaccination data was retrieved from the health registries.ResultsVaccination coverage of children aged 6–23 months was 22–47% against seasonal influenza and 80% against the A(H1N1)pdm09 virus in the pandemic season 2009–2010. During 3 influenza seasons, 1607 nasal swab samples were collected. Influenza was confirmed in 56 (6.1%) of 923 children (16 A(H1N1), 14 A(H3N2), and 26 B viruses). The incidence of influenza was 5.1% in 2008–2009, 2.7% in 2009–2010, and 5.0% in 2010–2011. Effectiveness of the adjuvanted vaccine against the pandemic influenza A(H1N1)pdm09 was 97% (95% confidence interval, 76–100%). Three children with influenza were hospitalized.ConclusionThe yearly incidence of seasonal influenza was 5% in this cohort of very young children with variable influenza vaccine coverage. Adjuvanted vaccine against the pandemic influenza was highly effective. Both seasonal and pandemic influenza cases were mostly non-severe.     

Substitution of lysine at 627 position in PB2 protein does not change virulence of the 2009 pandemic H1N1 virus in mice

A lysine at the 627 position (627K) of PB2 protein of influenza virus has been recognized as a determinant for host adaptation and a virulent element for some influenza viruses. While seasonal influenza viruses exclusively contained 627K, the pandemic (H1N1) 2009 possessed a glutamic acid (627E), even after circulation in humans for more than 6 months. To explore the potential role of E627K substitution in PB2 in the pandemic (H1N1) 2009 virus, we compared pathogenicity and growth properties between a recombinant virus containing 627K PB2 gene and the parental A/California/4/2009 strain containing 627E. Our results showed that substitution of 627K in PB2 gene does not confer higher virulence and growth rate for the pandemic (H1N1) 2009 virus in mice and cell culture respectively, suggesting 627K is not required for human adaptation of the pandemic (H1N1) 2009 virus.     

Human coronavirus NL-63 infection in a Brazilian patient suspected of H1N1 2009 influenza infection: Description of a fatal case

Human coronaviruses (HCoVs) cause upper respiratory tract and occasionally lower respiratory tract diseases. The recently described human coronavirus NL63 has not been well investigated among Brazilian patients. We reported the clinical course of an HCoV-NL63 infection in a hospitalised patient suspected of H1N1 2009 infection during the second pandemic wave of influenza activity. A 46-year-old female, health care worker with diabetes and presenting with influenza-like illness (ILI) was admitted to the hospital. During 9 days of influenza-like symptoms, the patient had diabetes decompensation, haemorrhagic pneumonia, rhabdomyolysis, respiratory and renal failure, pericarditis, and brain edema and died. HCoV-NL63 may be a causative agent of previously unexplained respiratory illnesses.     

2009 pandemic H1N1-associated myocarditis in a previously healthy adult

Influenza infection most commonly affects the upper and lower respiratory tracts, but can involve extrapulmonary sites, including the myocardium. We report on a case of myocarditis caused by documented 2009 pandemic H1N1 influenza in a previously healthy adult, and review the literature on influenza myocarditis.