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.     

Performance of rapid-test kits for the detection of the pandemic influenza A/H1N1 virus

The early detection of pandemic influenza strains is a key factor for clinicians in treatment decisions and infection control practices. The aims of this study were to determine the analytical sensitivity and clinical performance of the commercially available influenza rapid tests in Taiwan. Four rapid tests for influenza virus (BinaxNow test, QuickVue test, TRU test, and Formosa Rapid test) were evaluated for their detection limit against four influenza viruses (the 2009 pandemic influenza A virus H1N1, seasonal influenza virus H1N1, H3N2, and influenza B virus) circulating in Taiwan. The viral load of these isolates were quantified by rtRT-PCR and then diluted 2-fold serially for the comparison. The lowest detectable viral load of the pandemic influenza A virus H1N1 by the Formosa Rapid test, QuickVue test, TRU test, and Binax Now test was 5.3 × 10⁴, 1.0 × 10⁵, 1.0 × 10⁵, and 4.2 × 10⁵ copies/μL, respectively. Of these four tests, the two most sensitive tests (the QuickVue test and the Formosa Rapid test) were chosen to evaluate 62 nasopharyngeal specimens from patients who were suspected of infection with pandemic influenza A virus H1N1. The positive rate for the Formosa Rapid test and the QuickVue test were 53.2% (33/62) and 45.2% (28/62) (McNemar's test, P = 0.125), respectively. In conclusion, the Formosa Rapid test was the most sensitive test in the present study for the detection of influenza antigens and its clinical performance was similar to that of the QuickVue test (Kappa = 0.776). This suggests that the Formosa Rapid test could be used to aid clinical decision making in primary health care settings during outbreaks of influenza.     

Severe outcome of influenza A/H1N1/09v infection associated with 222G/N polymorphisms in the haemagglutinin: a multicentre study

In a multicentre study, influenza A/H1N1/09v 222G/N variants were more frequently detected in patients admitted to the intensive-care unit for invasive mechanical ventilation or extracorporeal membrane oxygenation (10/23; 43.5%) than in patients hospitalized in other units (2/27; 7.4%) and community patients (0/81; 0.0%) (p <0.01). A significantly higher virus load (p 0.02) in the lower vs the upper respiratory tract was observed. Predominance of 222G/N variants in the lower respiratory tract (40% of total virus population) vs the upper respiratory tract (10%) was shown by clonal analysis of haemagglutinin sequences in paired nasal swab and bronchoalveolar lavage samples. The time from illness onset to sampling was significantly longer in patients with severe infection vs community patients (p <0.001). It was concluded that the 222G/N variants showed increased virulence; mutant variants were probably selected in individual patients; and the longer duration of illness might have favoured the emergence of adaptive mutations through multiple replication cycles.     

Predictors of H1N1 influenza in the emergency department: proposition for a modified H1N1 case definition

Reliable and rapid diagnosis of influenza A H1N1 is essential to initiate appropriate antiviral therapy and preventive measures. We analysed the differences in clinical presentation and laboratory parameters between emergency department patients with PCR-confirmed H1N1 influenza infection (n = 199) and those with PCR-negative influenza-like illness (ILI; n = 252). Cough, wheezing, leucopenia, eosinopenia and a lower C-reactive protein remained significant predictors of H1N1 influenza. Proposed combinations of clinical symptoms with simple laboratory parameters (e.g. reported or measured fever and either cough or leucocytes <8.5 × 10⁹/L) were clearly superior to currently used official ILI case definitions that use clinical criteria alone.     

Transmission of influenza A/H5N1 viruses in mammals

Highly pathogenic avian H5N1 influenza A viruses occasionally infect humans and cause severe respiratory disease and fatalities. Currently, these viruses are not efficiently transmitted from person to person, although limited human-to-human transmission may have occurred. Nevertheless, further adaptation of avian H5N1 influenza A viruses to humans and/or reassortment with human influenza A viruses may result in aerosol transmissible viruses with pandemic potential. Although the full range of factors that modulate the transmission and replication of influenza A viruses in humans are not yet known, we are beginning to understand some of the molecular changes that may allow H5N1 influenza A viruses to transmit via aerosols or respiratory droplets among mammals. A better understanding of the biological basis and genetic determinants that confer transmissibility to H5N1 influenza A viruses in mammals is important to enhance our pandemic preparedness.     

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.     

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.     

Utility of the rapid antigen detection BinaxNOW Influenza A&B test for detection of novel influenza A (H1N1) virus

Nasopharyngeal aspirates, collected during outbreaks, of the novel influenza A (H1N1) virus in Barcelona, were used to compare the accuracy of a rapid antigen-based test (Binax) with the real-time RT-PCR assay developed by the CDC. The sensitivity, specificity and positive predictive value of the rapid test are higher in patients less than 18 years old and during the acute stage of the epidemic than in adult patients.     

Immunogenicity of influenza A/USSR (H1N1) subunit vaccine in unprimed young adults

Purified subunit vaccines (HANAflu) containing 20 /xg of hemagglutinin of influenza A/USSR/90/77 (H1N1) alone or with 1–5% whole virus were compared to commercially available vaccines for reactogenicity and immunogenicity in unprimed young adults. Reactions to all vaccines were minimal. Sera from volunteers who received two intramuscular doses of vaccine or placebo were tested by hemagglutination-inhibition and neutralization tests. HANAflu with 1 m?g (5%) whole virus added was not different in immunogenicity from commercial vaccine. Both commercial vaccine and HANAflu with 1 m?g whole virus added gave higher seroconversion rates and more neutralization titers ≥ 4 log₂ than HANAflu alone and HANAflu + 0.2 m?g (1%) whole virus. Thus, the HANAflu subunit vaccine alone was less immunogenic than commercial vaccine in unprimed persons. However, addition of 1 m?g (5%) whole virus, but not 0.2 m?g (1%), eliminated this difference. There may be a role for addition of small amounts of whole virus to subunit influenza vaccines to overcome lower immunogenicity in unprimed populations.     

Pandemic influenza A(H1N1)pdm09: risk of infection in primary healthcare workers

Background

Healthcare workers in primary care are at risk of infection during an influenza pandemic. The 2009 influenza pandemic provided an opportunity to assess this risk.

Aim

To measure the prevalence of seropositivity to influenza A(H1N1)pdm09 among primary healthcare workers in Canterbury, New Zealand, following the 2009 influenza pandemic, and to examine associations between seropositivity and participants’ sociodemographic characteristics, professional roles, work patterns, and seasonal influenza vaccination status.

Design and setting

An observational study involving a questionnaire and testing for influenza A(H1N1)pdm09 seropositivity in all primary healthcare workers in Canterbury, New Zealand between December 2009 and February 2010.

Method

Participants completed a questionnaire that recorded sociodemographic and professional data, symptoms of influenza-like illness, history of seasonal influenza vaccination, and work patterns. Serum samples were collected and haemagglutination inhibition antibody titres to influenza A(H1N1)pdm09 measured.

Results

Questionnaires and serum samples were received from 1027 participants, from a workforce of 1476 (response rate 70%). Seropositivity was detected in 224 participants (22%). Receipt of seasonal influenza vaccine (odds ratio [OR] = 2.0, 95% confidence interval [CI] = 1.2 to 3.3), recall of influenza (OR = 1.9, 95% CI = 1.3 to 2.8), and age ≤45 years (OR = 1.4, 95% CI = 1.0 to 1.9) were associated with seropositivity.

Conclusion

A total of 22% of primary care healthcare workers were seropositive. Younger participants, those who recalled having influenza, and those who had been vaccinated against seasonal influenza were more likely to be seropositive. Working in a dedicated influenza centre was not associated with an increased risk of seropositivity.     

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.     

Response of BALB/c mice to a monovalent influenza A （H1N1） 2009 split vaccine

The novel influenza A (H1N1) 2009 virus has emerged to cause the first pandemic of the twenty-first century. Disease outbreaks caused by the influenza A (H1N1) virus have prompted concerns about the potential for a pandemic and have driven the development of vaccines against this subtype of influenza A. In this study, we developed a monovalent influenza A (H1N1) split vaccine and evaluated its effects in BALB/c mice. Mice were immunized subcutaneously with 2 doses of the vaccine containing hemagglutinin (HA) alone or HA plus an aluminum hydroxide (Al(OH)₃) adjuvant. Immunization with varying doses of HA (3.75, 7.5, 15, 30, 45 or 60 µg) was performed to induce the production of neutralizing antibodies. The vaccine elicited strong hemagglutination inhibition (HI) and microneutralization, and addition of the adjuvant augmented the antibody response. A preliminary safety evaluation showed that the vaccine was not toxic at large doses (0.5 ml containing 60 µg HA+600 µg Al(OH)₃ or 60 µg HA). Moreover, the vaccine was found to be safe at a dose of 120 µg HA+1200 µg Al(OH)₃ or 120 µg HA in 1.0 ml in rats. In conclusion, the present study provides support for the clinical evaluation of influenza A (H1N1) vaccination as a public health intervention to mitigate a possible pandemic. Additionally, our findings support the further evaluation of the vaccine used in this study in primates or humans.     

Antigen-specific H1N1 influenza antibody responses in acute respiratory tract infections and their relation to influenza infection and disease course

BackgroundEarly antibody responses to influenza infection are important in both clearance of virus and fighting the disease. Acute influenza antibody titers directed toward H1-antigens and their relation to infection type and patient outcomes have not been well investigated.ObjectiveUsing hemagglutination inhibition (HI) assays, we aimed to characterize the H1-specific antibody titers in patients with influenza infection or another respiratory infection before and after the H1N1-pandemic influenza outbreak. Among patients with acute influenza infection we related duration of illness, severity of symptoms, and need for hospitalization to antibody titers.MethodsThere were 134 adult patients (average age 34.7) who presented to an urban academic emergency department (ED) from October through March during the 2008–2011 influenza seasons with symptoms of fever and a cough. Nasal aspirates were tested by viral culture, and peripheral blood serum was run in seven H1-subtype HI assays.ResultsAcutely infected influenza patients had markedly lower antibody titers for six of the seven pseudotype viruses. For the average over the seven titers (log units, base 2) their mean was 7.24 (95% CI 6.88, 7.61) compared with 8.60 (95% CI 8.27, 8.92) among patients who had a non-influenza respiratory illness, p < 0.0001. Among patients with seasonal influenza infection, titers of some antibodies correlated with severity of symptoms and with total duration of illness (p < 0.02).ConclusionIn patients with acute respiratory infections, lower concentrations of H1-influenza-specific antibodies were associated with influenza infection. Among influenza-infected patients, higher antibody titers were present in patients with a longer duration of illness and with higher severity-of-symptom scores.     

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。     

时空扫描方法在北京市甲型H1N1流感聚集性探测中的应用

目的 探讨北京市2009年甲型H1N1流感发病时空分布特征,为传染病预防控制提供理论依据.方法 利用SaTScan8.0软件进行时空扫描分析,通过ArcGIS8.3软件呈现甲型H1N1流感时空聚集区域.结果 按照7天、14天、30天,50％的时间周期进行单纯时间扫描分析,结果显示甲型H1N1流感发病在9月4日-12月1...