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Background The Global Influenza Hospital Surveillance Network (GIHSN) was established in 2012 to conduct coordinated worldwide influenza surveillance. Here we describe underlying comorbidities, symptoms, and outcomes in hospitalized patients with influenza. Methods Between November/2018 and October/2019, GIHSN included 19 sites in 18 countries using a standardized surveillance protocol. Influenza infection was laboratory-confirmed with RT-PCR. A multivariate logistic regression model was utilized to analyze the extent to which various risk factors predict severe outcomes. Results Of 16,022 enrolled patients, 21,9% had laboratory-confirmed influenza; 49.2% of influenza cases were A/H1N1pdm09. Fever and cough were the most common symptoms, though they decreased with age (p Conclusions Both virus and host factors contributed to influenza burden. We identified age differences in comorbidities, presenting symptoms, and adverse clinical outcomes among those hospitalized with influenza, and benefit from influenza vaccination in protecting against adverse clinical outcomes. The GIHSN provides an ongoing platform for global understanding of hospitalized influenza illness.

BackgroundInfluenza disease data remain scarce in middle and lower-income countries. We used data from the Global Influenza Hospital Surveillance Network (GIHSN), a prospective multi-country surveillance system from 2012-2019, to assess differences in the epidemiology and severity of influenza hospitalizations by country income level.MethodsWe compiled individual-level data on acute respiratory hospitalizations, with standardized clinical reporting and testing for influenza. Adjusted odds ratios (aORs) for influenza-associated intensive care unit (ICU) admission and in-hospital death were estimated with multivariable logistic regression that included country income group (World Bank designation: high-income countries: HIC; upper middle-income countries: UMIC; lower middle-income countries: LMIC), age, sex, number of comorbidities, influenza subtype and lineage, and season as covariates.FindingsFrom 73,121 patients hospitalized with respiratory illness in 22 countries, 15,660 were laboratory-confirmed for influenza. After adjustment for patient-level covariates, there was a two-fold increased risk of ICU admission for patients in UMIC (aOR 2.31; 95% confidence interval (CI) 1.85-2.88, p < 0.001), and a 5-fold increase in LMIC (aOR 5.35; 95% CI 3.98-7.17, p < 0.001), compared to HIC. The risk of in-hospital death in HIC and UMIC was comparable (UMIC: aOR 1.14; 95% 0.87-1.50; p > 0.05), though substantially lower than that in LMIC (aOR 5.05; 95% 3.61-7.03; p < 0.001 relative to HIC). A similar severity increase linked to country income was found in influenza-negative patients.InterpretationWe found significant disparities in influenza severity among hospitalized patients in countries with limited resources, supporting global efforts to implement public health interventions.FundingThe GIHSN is partially funded by the Foundation for Influenza Epidemiology (France). This analysis was funded by Ready2Respond under Wellcome Trust grant 224690/Z/21/Z.Research in ContextEvidence before this studyIn the past 35 years, fewer than 10% of peer-reviewed articles on influenza burden of disease have reported analyses from lower middle- or lower-income settings. Whereas the impact of influenza in upper middle- and high-income countries – regions where influenza seasonality is well-defined and where high numbers of influenza-related clinic visits, hospital admissions, and deaths are well-documented – has been clearly quantified, data scarcity has challenged our ability to ascertain influenza burden in resource-limited settings. As a result, policy decisions on vaccine use in lower-income countries have been made with limited data, slowing the development of influenza vaccine recommendations in these settings. In this study, we have conducted prospective influenza surveillance in the hospital setting in multiple countries to assess potential geographic differences in the severity of influenza admissions and have shown that influenza is a global concern, and report poorer clinical outcomes among patients admitted to hospitals in resource-limited settings. In these settings, it is especially important to consider the role of preventive measures, such as vaccines, in providing protection against severe disease.Added value of this studySince 2012, in collaboration with over 100 clinical sites worldwide, the Global Influenza Hospital Surveillance Network (GIHSN) has provided patient-level data on severe influenza-like illnesses based on a core protocol and consistent case definitions. To our knowledge, this is the first study to analyze multiple years of global, patient-level data generated by prospective, hospital-based surveillance across a large number of countries to investigate geographic differences in both influenza morbidity and mortality. Our study provides information on influenza burden in under-researched populations, particularly those in lower middle-income countries, and highlights the need for continued global collaboration and unified protocols to better understand the relationships between socio-economic development, healthcare, access to care, and influenza morbidity and mortality.After adjustment for differences in the characteristics of individual patients admitted to the hospital for influenza, we find an increased severity of disease in lower-income settings. In particular, the risk of ICU admissions increases two- and five-fold in upper middle- and lower-middle income countries, compared to high-income countries. The risk of in-hospital death is five-fold higher in lower-middle income countries, compared to more affluent countries.Implications of all the available evidenceWe find evidence of increased severity in influenza admissions in lower-income countries, which could point at structural differences in access to care between countries (patients arriving at the hospital later in the disease process) and/or differences in care once in the hospital. Understanding the mechanisms responsible for these disparities will be important to improve management of influenza, optimize vaccine allocation, and mitigate global disease burden. The Global Influenza Hospital Surveillance Network serves as an example of a collaborative platform that can be expanded and leveraged to address geographic differences in the epidemiology and severity of influenza, especially in lower and upper middle-income countries.

Global estimates showed an estimate of up to 650,000 seasonal influenza-associated respiratory deaths annually. However, the mortality rate of seasonal influenza is unknown for most countries in the WHO Eastern Mediterranean Region, including Iran. We aimed to estimate the excess mortality attributable to seasonal influenza in Kerman province, southeast Iran for the influenza seasons 2006/2007-2011/2012.We applied a Serfling model to the weekly total pneumonia and influenza (PI) mortality rate during winter to define the epidemic periods and to the weekly age-specific PI, respiratory, circulatory, and all-cause deaths during non-epidemic periods to estimate baseline mortality. The excess mortality was calculated as the difference between observed and predicted mortality. Country estimates were obtained by multiplying the estimated annual excess death rates by the populations of Iran.We estimated an annual average excess of 40 PI, 100 respiratory, 94 circulatory, and 306 all-cause deaths attributable to seasonal influenza in Kerman; corresponding to annual rates of 1.4 (95% confidence interval [CI] 1.1-1.8) PI, 3.6 (95% CI 2.6-4.8) respiratory, 3.4 (95% CI 2.1-5.2) circulatory, and 11.0 (95% CI 7.3-15.6) all-cause deaths per 100,000 population. Adults ≥75 years accounted for 56% and 53% of all excess respiratory and circulatory deaths, respectively. At country level, we would expect an annual of 1119 PI to 8792 all-cause deaths attributable to seasonal influenza.Our findings help to define the mortality burden of seasonal influenza, most of which affects adults aged ≥75 years. This study supports influenza prevention and vaccination programs in older adults.

BackgroundInfluenza is a major year-round cause of respiratory illness in Kenya, particularly in children under 5. Current influenza vaccines result in short-term, strain-specific immunity and were found in a previous study not to be cost-effective in Kenya. However, next generation vaccines are in development that may have a greater impact and cost-effectiveness profile.MethodsWe expanded a model previously used to evaluate cost-effectiveness of seasonal influenza vaccines in Kenya to include next generation vaccines by allowing for enhanced vaccine characteristics and multi-annual immunity. We specifically examined vaccinating children under 5 years of age with improved vaccines, evaluating vaccines with combinations of increased vaccine effectiveness, cross protection between strains (breadth) and duration of immunity. We evaluated cost-effectiveness using incremental cost-effectiveness ratios (ICERs) and incremental net monetary benefits (INMBs) for a range of values for the willingness-to-pay (WTP) per DALY averted. Finally, we estimated threshold per-dose vaccine prices at which vaccination becomes cost-effective.ResultsNext generation vaccines can be cost-effective, dependent on the vaccine characteristics and assumed WTP thresholds. Universal vaccines (assumed to provide long-term and broad immunity) are most cost-effective in Kenya across three of four WTP thresholds evaluated, with the lowest median value of ICER per DALY averted ($263, 95% Credible Interval (CrI): $-1698, $1061) and the highest median INMBs. At a WTP of $623, universal vaccines are cost-effective at or below a median price of $5.16 per dose (95% CrI: $0.94, $18.57). We also show that the assumed mechanism underlying infection-derived immunity strongly impacts vaccine outcomes.ConclusionThis evaluation provides evidence for country-level decision makers about future next generation vaccine introduction, as well as global research funders about the potential market for these vaccines. Next generation vaccines may offer a cost-effective intervention to reduce influenza burden in low-income countries with year-round seasonality like Kenya.

Summary Background Maternal influenza immunisation can reduce morbidity and mortality associated with influenza infection in pregnant women and young infants. We aimed to determine the vaccine efficacy of maternal influenza immunisation against maternal and infant PCR-confirmed influenza, duration of protection, and the effect of gestational age at vaccination on vaccine efficacy, birth outcomes, and infant growth up to 6 months of age. Methods We did a pooled analysis of three randomised controlled trials done in Nepal (2011–2014), Mali (2011–2014), and South Africa (2011–2013). Pregnant women, gestational age 17–34 weeks in Nepal, 28 weeks or more in Mali, and 20–36 weeks in South Africa, were enrolled. Women were randomly assigned 1:1 to a study group, in which they received trivalent inactivated influenza vaccine (IIV) in all three trials, or a control group, in which they received saline placebo in Nepal and South Africa or quadrivalent meningococcal conjugate vaccine in Mali. Enrolment at all sites was complete by April 24, 2013. Infants and women were assessed for respiratory illness, and samples from those that met the case definition were tested for influenza by PCR testing. Growth measurements, including length and weight, were obtained at birth at all sites, at 24 weeks in South Africa, and at 6 months in Nepal and Mali. The three trials are registered with ClinicalTrials.gov , numbers NCT01430689 , NCT01034254 , and NCT02465190 . Findings 10 002 women and 9800 liveborn infants were included. Pooled efficacy of maternal vaccination to prevent infant PCR-confirmed influenza up to 6 months of age was 35% (95% CI 19 to 47). The pooled estimate was 56% (28 to 73) within the first 2 months of life, 39% (11 to 58) between 2 and 4 months, and 19% (–9 to 40) between 4 and 6 months. In women, from enrolment during pregnancy to the end of follow-up at 6 months postpartum, the vaccine was 50% (95% CI 32–63) efficacious against PCR-confirmed influenza. Efficacy was 42% (12 to 61) during pregnancy and 60% (36 to 75) postpartum. In women vaccinated before 29 weeks gestational age, the estimated efficacy was 30% (–2 to 52), and in women vaccinated at or after 29 weeks, efficacy was 71% (50 to 83). Efficacy was similar in infants born to mothers vaccinated before or after 29 weeks gestation (34% [95% CI 12 to 51] vs 35% [11 to 52]). There was no overall association between maternal vaccination and low birthweight, stillbirth, preterm birth, and small for gestational age. At 6 months of age, the intervention and control groups were similar in terms of underweight (weight-for-age), stunted (length-for-age), and wasted (weight-for-length). Median centile change from birth to 6 months of age was similar between the intervention and the control groups for both weight and length. Interpretation The assessment of efficacy for women vaccinated before 29 weeks gestational age might have been underpowered, because the point estimate suggests that there might be efficacy despite wide CIs. Estimates of efficacy against PCR-confirmed influenza and safety in terms of adverse birth outcomes should be incorporated into any further consideration of maternal influenza immunisation recommendations. Funding Bill & Melinda Gates Foundation.

To assess the stability of improvements in global respiratory virus surveillance in countries supported by the United States Centers for Disease Control and Prevention (CDC) after reductions in CDC funding and with the stress of the coronavirus disease 2019 (COVID-19) pandemic.We assessed whether national influenza surveillance systems of CDC-funded countries: (i) continued to analyse as many specimens between 2013 and 2021; (ii) participated in activities of the World Health Organization's (WHO) Global Influenza Surveillance and Response System; (iii) tested enough specimens to detect rare events or signals of unusual activity; and (iv) demonstrated stability before and during the COVID-19 pandemic. We used CDC budget records and data from the WHO Global Influenza Surveillance and Response System.While CDC reduced per-country influenza funding by about 75% over 10 years, the number of specimens tested annually remained stable (mean 2261). Reporting varied substantially by country and transmission zone. Countries funded by CDC accounted for 71% (range 61-75%) of specimens included in WHO consultations on the composition of influenza virus vaccines. In 2019, only eight of the 17 transmission zones sent enough specimens to WHO collaborating centres before the vaccine composition meeting to reliably identify antigenic variants.Great progress has been made in the global understanding of influenza trends and seasonality. To optimize surveillance to identify atypical influenza viruses, and to integrate molecular testing, sequencing and reporting of severe acute respiratory syndrome coronavirus 2 into existing systems, funding must continue to support these efforts.Évaluer la stabilité des améliorations en matière de surveillance mondiale des virus respiratoires dans les pays soutenus par les Centers for Disease Control and Prevention (CDC) des États-Unis d'Amérique, après les baisses de financement des CDC et avec le stress causé par la pandémie de maladie à coronavirus 2019 (COVID-19).Nous avons examiné les mécanismes nationaux de surveillance de la grippe dans les pays financés par les CDC pour déterminer: (i) s'ils continuaient à analyser le même nombre d'échantillons entre 2013 et 2021; (ii) s'ils participaient à des activités du Système mondial de surveillance de la grippe et de riposte mis en place par l'Organisation mondiale de la Santé (OMS); (iii) s'ils testaient suffisamment d'échantillons pour détecter des événements rares ou des signes d'activité inhabituelle; et enfin, (iv) s'ils faisaient preuve de stabilité avant et pendant la pandémie de maladie à coronavirus 2019 (COVID-19). Nous avons utilisé les documents budgétaires des CDC, ainsi que les données du Système mondial OMS de surveillance de la grippe et de riposte.Bien que les CDC aient réduit d'environ 75% leur financement aux différents pays pour étudier la grippe au cours de la décennie écoulée, le nombre d'échantillons testés chaque année est resté stable (2261 en moyenne). Les signalements variaient fortement en fonction du pays et de la zone de transmission. Les pays financés par les CDC représentaient 71% (plage comprise entre 61% et 75%) des échantillons inclus dans les consultations de l'OMS sur la composition des vaccins contre les virus grippaux. En 2019, seulement huit des 17 zones de transmission ont envoyé suffisamment d'échantillons aux centres collaborant avec l'OMS pour identifier avec certitude les variants antigéniques avant la réunion sur la composition des vaccins.Des progrès considérables ont été réalisés en matière de compréhension des tendances et du caractère saisonnier de la grippe. Néanmoins, le financement doit se poursuivre afin d'améliorer la surveillance et, par conséquent, d'identifier les virus grippaux atypiques, mais aussi d'intégrer les tests moléculaires, le séquençage et le signalement du coronavirus 2 du syndrome respiratoire aigu sévère dans les systèmes existants.Valorar la estabilidad de las mejoras en la vigilancia mundial de los virus respiratorios en los países que reciben apoyo de los Centros para el Control y la Prevención de Enfermedades (CDC) de los Estados Unidos después de las reducciones en la financiación de los CDC y ante la situación de estrés por la pandemia de la enfermedad por coronavirus de 2019 (COVID-19).Se analizó si los sistemas nacionales de vigilancia de la influenza de los países que reciben fondos de los CDC: i) seguían analizando la misma cantidad de muestras entre 2013 y 2021; ii) participaban en las actividades del Sistema Mundial de Vigilancia y Respuesta a la Gripe de la Organización Mundial de la Salud (OMS); iii) analizaban suficientes muestras para detectar acontecimientos raros o señales de actividad inusual; y iv) demostraban estabilidad antes y durante la pandemia de la enfermedad por coronavirus de 2019 (COVID-19). Se utilizaron los registros de presupuesto de los CDC y los datos del Sistema Mundial de Vigilancia y Respuesta a la Gripe de la OMS.Aunque los CDC redujeron los fondos destinados a la gripe por país en casi un 75 % a lo largo de 10 años, el número de muestras analizadas al año se mantuvo estable (media de 2261). Los informes variaron de manera sustancial según el país y la zona de transmisión. Los países que recibieron financiación de los CDC representaron el 71 % (rango entre el 61 y el 75 %) de las muestras incluidas en las consultas de la OMS sobre la composición de las vacunas antigripales. En 2019, solo ocho de las 17 zonas de transmisión enviaron suficientes muestras a los centros colaboradores de la OMS antes de la reunión sobre la composición de la vacuna para identificar de una manera fiable las variantes antigénicas.Se ha logrado un gran progreso en la comprensión global de las tendencias y la estacionalidad de la gripe. Para optimizar la vigilancia con el fin de identificar los virus atípicos de la gripe e integrar las pruebas moleculares, la secuenciación y la notificación del coronavirus del síndrome respiratorio agudo grave de tipo 2 en los sistemas existentes, la financiación debe seguir apoyando estos esfuerzos.الغرض تقييم استقرار التحسينات في المراقبة العالمية لفيروس الجهاز التنفسي في الدول التي تدعمها المراكز الأمريكية لمكافحة الأمراض والوقاية منها (CDC)، بعد التخفيضات في تمويل هذه المراكز، ومع ضغط جائحة مرض فيروس كورونا 2019 (كوفيد 19). الطريقة قمنا بتقييم ما إذا كانت الأنظمة الوطنية لمراقبة الإنفلونزا في الدول التي تمولها المراكز الأمريكية لمكافحة الأمراض والوقاية منها: (1) واصلت تحليل العديد من العينات بين عامي 2013 و2021؛ و(2) شارك في أنشطة النظام العالمي لمراقبة الإنفلونزا والاستجابة التابع لمنظمة الصحة العالمية؛ و(3) فحصت عينات كافية لاكتشاف الأحداث والإشارات النادرة للنشاط غير العادي؛ و(4) أظهرت الاستقرار قبل وأثناء جائحة مرض فيروس كورونا 2019 (كوفيد 19). واستخدمنا سجلات وبيانات ميزانية مراكز CDC من النظام العالمي لمراقبة الإنفلونزا والاستجابة التابع لمنظمة الصحة العالمية. النتائج بينما خفضت مراكز CDC تمويل الإنفلوانزا لكل دولة بنحو 75% على مدى 10 سنوات، فإن عدد العينات التي يتم فحصها سنويًا ظل مستقرًا (متوسط 2261). اختلفت التقارير بشكل كبير حسب الدولة ومنطقة الإرسال. إن الدول التي حصلت على تمويل من مراكز CDC شكلت 71% (المدى 61 إلى 75%) من العينات المتضمنة في استشارات منظمة الصحة العالمية حول تكوين لقاحات فيروس الإنفلونزا. في عام 2019، ثمانية فقط من مناطق الانتقال الـ 17 أرسلت عينات كافية إلى المراكز المتعاونة مع منظمة الصحة العالمية قبل اجتماع تكوين اللقاح لتحديد المتغيرات المستضدية بشكل موثوق. الاستنتاج تم إحراز تقدم كبير في الفهم العالمي لاتجاهات ومواسم الأنفلونزا. لتحسين المراقبة لتحديد فيروسات الأنفلونزا غير المعتادة، ودمج الفحص الجزيئي، والتسلسل، والإبلاغ عن متلازمة الالتهاب التنفسي الحاد الوخيم فيروس كورونا 2 في الأنظمة الحالية، يجب أن يستمر التمويل في دعم هذه الجهود.旨在评估由美国疾病控制和预防中心 (CDC) 支持的国家在 CDC 资金减少和新型冠状病毒肺炎大流行压力下的全球呼吸系统病毒监测改善情况的稳定性。.我们评估了 CDC 资助的国家的国家流感监测系统是否：(i) 继续尽可能多地分析 2013 至 2021 年间的样本；(ii) 参与了世界卫生组织 (WHO) 的全球流感监测和应对系统的活动；(iii) 测试了足够多的样本以检测小概率事件或异常活动信号；以及 (iv) 在新型冠状病毒肺炎大流行之前和期间表现出稳定性。我们使用了 CDC 预算记录和世卫组织全球流感监测和应对系统的数据。.虽然 CDC 在 10 年内将每个国家的流感基金减少了约 75%，但每年测试的样本数量保持稳定（平均 2261 份）。报告因国家和传播区而异。由 CDC 资助的国家的样本占世卫组织磋商的流感病毒疫苗组合物中包含的样本的 71%（范围为 61-75%）。在 2019 年，17 个传播区中仅八个区域在疫苗组合物大会之前向世卫组织合作中心发送了足够数量的样本，以供识别抗原变体。.全球对流感趋势和季节性的认识取得很大进展。要优化监测以识别非典型流感病毒，并将严重急性呼吸综合征冠状病毒 2 的分子检测、测序和报告整合到现有系统中，必须持续投入资金予以支持。.Оценить стабильность улучшений в глобальном эпиднадзоре за респираторными вирусами в странах, поддерживаемых центрами США по контролю и профилактике заболеваний (CDC), после сокращения финансирования со стороны центров CDC, а также в условиях стресса, вызванного пандемией коронавирусной инфекции 2019 года (COVID-19).Авторы оценили следующие моменты: (i) продолжали ли национальные системы эпиднадзора за гриппом в странах, финансируемых центрами CDC, анализировать одно и то же количество образцов в период с 2013 по 2021 г.; (ii) участвовали ли эти системы в деятельности Глобальной системы Всемирной организации здравоохранения (ВОЗ) по эпиднадзору за гриппом и принятию ответных мер; (iii) протестировали ли эти системы достаточное количество образцов для выявления редких случаев заболевания или сигналов необычной активности; (iv) продемонстрировали ли эти системы стабильность до и во время пандемии коронавирусной инфекции 2019 года (COVID-19). Авторы использовали бюджетные документы центров CDC и данные из Глобальной системы ВОЗ по эпиднадзору за гриппом и принятию ответных мер.Несмотря на то что центры CDC сократили финансирование на борьбу с гриппом в расчете на одну страну примерно на 75% за 10 лет, количество ежегодно тестируемых образцов оставалось стабильным (в среднем 2261). Отчетность существенно различалась в зависимости от страны и зоны передачи заболевания. На страны, финансируемые центрами CDC, приходился 71% (диапазон 61–75%) образцов, включенных в консультации ВОЗ по составу вакцин против вируса гриппа. В 2019 г. только восемь из 17 зон передачи вируса отправили достаточное количество образцов в сотрудничающие центры ВОЗ до проведения совещания по составу вакцины для надежной идентификации антигенных вариантов.В глобальном понимании тенденций и сезонности гриппа достигнут значительный прогресс. Чтобы оптимизировать эпиднадзор для выявления атипичных вирусов гриппа и интегрировать молекулярное тестирование, секвенирование и отчетность о тяжелом остром респираторном синдроме коронавируса-2 в существующие системы, следует продолжить финансирование для поддержки этих усилий.

Infectious diseases continue to represent a significant threat to global health security, particularly in the context of increasing globalization, interconnectedness and interdependence. Chief among such threats are influenza viruses and other respiratory pathogens, such as Middle East Respiratory Syndrome coronavirus (MERS-CoV), because of their risk of high transmissibility and acuity of illness. Annual epidemics of seasonal influenza cause an estimated 3-5 million cases of severe illness and more than 500 000 deaths, with the prospect of pandemic influenza viruses causing far greater impact. In addition, the appearance of severe acute respiratory syndrome (SARS) in 2003, widespread and continued outbreaks of avian influenza A (H5N1) since 2004, the H1N1 pandemic in 2009 and emergence of MERS CoV in 2012 reflect the seriousness of public health challenges posed by influenza and emerging respiratory infections.

During May 22-September 10, 2016,* the United States experienced typical low levels of seasonal influenza activity overall; beginning in late August, clinical laboratories reported a slight increase in influenza positive test results and CDC received reports of a small number of localized influenza outbreaks caused by influenza A (H3N2) viruses. Influenza A (H1N1)pdm09, influenza A (H3N2), and influenza B viruses were detected during May-September in the United States and worldwide. The majority of the influenza viruses collected from the United States and other countries during that time have been characterized antigenically or genetically or both as being similar to the reference viruses representing vaccine components recommended for the 2016-17 Northern Hemisphere vaccine. During May 22-September 10, 2016, 20 influenza variant virus

Highlights • There is limited data on efficacy of yearly influenza vaccination in children aged, Background Few trials have evaluated influenza vaccine efficacy (VE) in young children, a group particularly vulnerable to influenza complications. We aimed to estimate VE against influenza in children aged

Antibody responses to influenza virus hemagglutinin provide protection against infection and are well studied. Less is known about the human antibody responses to the second surface glycoprotein, neuraminidase. Here, we assessed human antibody reactivity to a panel of N1, N2, and influenza B virus neuraminidases in different age groups, including children, adults, and the elderly. Using enzyme-linked immunosorbent assays (ELISA), we determined the breadth, magnitude, and isotype distribution of neuraminidase antibody responses to historic, current, and avian strains, as well as to recent isolates to which these individuals have not been exposed. It appears that antibody levels against N1 neuraminidases were lower than those against N2 or B neuraminidases. The anti-neuraminidase antibody levels increased with age and were, in general, highest against strains that circulated during the childhood of the tested individuals, providing evidence for “original antigenic sin.” Titers measured by ELISA correlated well with titers measured by the neuraminidase inhibition assays. However, in the case of the 2009 pandemic H1N1 virus, we found evidence of interference from antibodies binding to the conserved stalk domain of the hemagglutinin. In conclusion, we found that antibodies against the neuraminidase differ in magnitude and breadth between subtypes and age groups in the human population. (This study has been registered at ClinicalTrials.gov under registration no. NCT00336453, NCT00539981, and NCT00395174.), IMPORTANCE Anti-neuraminidase antibodies can afford broad protection from influenza virus infection in animal models and humans. However, little is known about the breadth and magnitude of the anti-neuraminidase response in the human population. Here we assessed antibody levels of children, adults, and the elderly against a panel of N1, N2, and type B influenza virus neuraminidases. We demonstrated that antibody levels measured by ELISA correlate well with functional neuraminidase inhibition titers. This is an important finding since ELISA is a simpler method than functional assays and can be implemented in high-throughput settings to analyze large numbers of samples. Furthermore, we showed that low titers of broadly cross-reactive antibodies against neuraminidase are prevalent in humans. By the use of an appropriate vaccination strategy, these titers could potentially be boosted to levels that might provide broad protection from influenza virus infection.

This report summarizes U.S. influenza activity* during October 2, 2016-February 4, 2017

CDC collects, compiles, and analyzes data on influenza activity year-round in the United States. The influenza season generally begins in the fall and continues through the winter and spring months; however, the timing and severity of circulating influenza viruses can vary by geographic location and season. Influenza activity in the United States remained low through October and November in 2015. Influenza A viruses have been most frequently identified, with influenza A (H3) viruses predominating. This report summarizes U.S. influenza activity for the period October 4-November 28, 2015.

Influenza activity in the United States began to increase in mid-November, remained elevated through February 21, 2015, and is expected to continue for several more weeks. To date, influenza A (H3N2) viruses have predominated overall. As has been observed in previous seasons during which influenza A (H3N2) viruses predominated, adults aged ≥65 years have been most severely affected. The cumulative laboratory-confirmed influenza-associated hospitalization rate among adults aged ≥65 years is the highest recorded since this type of surveillance began in 2005. This age group also accounts for the majority of deaths attributed to pneumonia and influenza. The majority of circulating influenza A (H3N2) viruses are different from the influenza A (H3N2) component of the 2014-15 Northern Hemisphere seasonal vaccines, and the predominance of these antigenically and genetically drifted viruses has resulted in reduced vaccine effectiveness. This report summarizes U.S. influenza activity* since September 28, 2014, and updates the previous summary.

The Advisory Committee on Immunization Practices recommends annual influenza vaccination for all persons aged ≥6 months to reduce morbidity and mortality caused by influenza in the United States. CDC previously developed a model to estimate that annual influenza vaccination resulted in 1.1-6.6 million fewer cases and 7,700-79,000 fewer hospitalizations per season during the 2005-2013 influenza seasons. For the 2013-14 influenza season, using updated estimates of vaccination coverage, vaccine effectiveness, and influenza hospitalizations, CDC estimates that influenza vaccination prevented approximately 7.2 million illnesses, 3.1 million medically attended illnesses, and 90,000 hospitalizations associated with influenza. Similar to prior seasons, fewer than half of persons aged ≥6 months are estimated to have been vaccinated. If influenza vaccination levels had reached the Healthy People 2020 target of 70%, an estimated additional 5.9 million illnesses, 2.3 million medically attended illnesses, and 42,000 hospitalizations associated with influenza might have been averted. For the nation to more fully benefit from influenza vaccines, more effort is needed to reach the Healthy People 2020 target.

During May 18-September 20, 2014, the United States experienced low levels of seasonal influenza activity overall. Influenza A (H1N1)pdm09 (pH1N1), influenza A (H3N2), and influenza B viruses were detected worldwide and were identified sporadically in the United States. In August, two influenza A (H3N2) variant viruses (H3N2v) were detected in Ohio. This report summarizes influenza activity in the United States and worldwide during May 18-September 20, 2014.

Influenza activity in the United States began to increase in mid-November and remained elevated through February 8, 2014. During that time, influenza A (H1N1)pdm09 (pH1N1) viruses predominated overall, while few B and A (H3N2) viruses were detected. This report summarizes U.S. influenza activity* during September 29, 2013-February 8, 2014, and updates the previous summary.

Please cite this paper as: Van Kerkhove et al. (2011) Epidemiologic and virologic assessment of the 2009 influenza A (H1N1) pandemic on selected temperate countries in the Southern Hemisphere: Argentina, Australia, Chile, New Zealand and South Africa. Influenza and Other Respiratory Viruses 5(6), e487–e498. Introduction and Setting Our analysis compares the most comprehensive epidemiologic and virologic surveillance data compiled to date for laboratory‐confirmed H1N1pdm patients between 1 April 2009 ‐ 31 January 2010 from five temperate countries in the Southern Hemisphere–Argentina, Australia, Chile, New Zealand, and South Africa. Objective We evaluate transmission dynamics, indicators of severity, and describe the co‐circulation of H1N1pdm with seasonal influenza viruses. Results In the five countries, H1N1pdm became the predominant influenza strain within weeks of initial detection. South Africa was unique, first experiencing a seasonal H3N2 wave, followed by a distinct H1N1pdm wave. Compared with the 2007 and 2008 influenza seasons, the peak of influenza‐like illness (ILI) activity in four of the five countries was 3‐6 times higher with peak ILI consultation rates ranging from 35/1,000 consultations/week in Australia to 275/100,000 population/week in New Zealand. Transmission was similar in all countries with the reproductive rate ranging from 1.2–1.6. The median age of patients in all countries increased with increasing severity of disease, 4–14% of all hospitalized cases required critical care, and 26–68% of fatal patients were reported to have ≥1 chronic medical condition. Compared with seasonal influenza, there was a notable downward shift in age among severe cases with the highest population‐based hospitalization rates among children

Influenza viruses cause annual epidemics in the United States. Although the severity of influenza epidemics vary by season, the morbidity associated with annual influenza epidemics in children is considerable from year to year. Excess pediatric outpatient clinic visits, emergency department visits, hospitalizations, and deaths occur each influenza season and are more common among younger children and those with conditions that increase their risk for developing influenza-related complications. Vaccination is the most effective way to prevent influenza and its complications and is recommended for all children 6 months through 18 years of age. Antiviral treatment is another tool to prevent influenza and reduce the duration of illness and complications. This article will review the virological, clinical, and epidemiological features of seasonal influenza, as well as discuss seasonal influenza vaccination and antiviral therapy.

Two new rotavirus vaccines have recently been licensed that will provide the intervention needed to diminish the huge burden of rotavirus disease among all children. In many upper and middle income countries, these vaccines will soon be available for the routine immunization of children. The impact should be a rapid and measurable reduction in hospitalizations and doctor visits for acute diarrhea in children, especially in the winter rotavirus season. While few deaths occur in these settings, the illness has consequences in terms of both medical costs and indirect costs, including parents work time lost. In the developing world, clinical trials are still needed to ensure that the vaccines being licensed will work as expected in children living in poor settings. In these settings, other enteric flora, micronutrient malnutrition, higher titers of maternal antibody and other factors still poorly defined have compromised other live oral vaccines and have required the developers to alter vaccine formulation, dose, or schedule. Until these trials are completed, we can only hope that the efficacy will be comparable and that the vaccine will prove to be life-savers. Once the efficacy and safety have been established, rotavirus vaccines could provide a major boost to programs for child survival.