2009 Pandemic influenza A (H1N1) deaths among children--United States, 2009-2010

Analysis of clinical characteristics and risk factors for death due to severe influenza in children

OBJECTIVE

The study analyzed the clinical features of children who had severe influenza and discussed on the risk factors associated with death in this population.

METHODS

A total of 167 children with severe influenza admitted to the intensive care unit of our hospital from January 2018 to August 2023 were selected and divided into the death group (27 cases) and the survival group (140 cases). Demographic characteristics and clinical data were collected and compared between the two groups. Logistic regression analysis was used to explore the risk factors for death in children with severe influenza.

RESULTS

The male-to-female ratio of the 167 children with severe influenza was 2.21:1, the median age was 3 years, and influenza A accounted for 70.66%. The CD4+ T cells percentage and CD4/CD8 were lower in the death group; the percentage of comorbid underlying diseases, mechanical ventilation, other systemic involvement, comorbid associated encephalopathy or encephalitis, and red blood cell distribution width (RDW), lactate dehydrogenase, activated partial thromboplastin time (APTT), and interleukin 6 were higher in the death group. The mechanical ventilation, associated encephalopathy or encephalitis, RDW, APTT, and CD4/CD8 were the independent risk factors for death.

CONCLUSION

Mechanical ventilation, comorbid encephalopathy or encephalitis, increased RDW, prolonged APTT, and decreased CD4/CD8 are independent risk factors for death in children with severe influenza.

Pandemics, past and present: The role of biological anthropology in interdisciplinary pandemic studies

Biological anthropologists are ideally suited for the study of pandemics given their strengths in human biology, health, culture, and behavior, yet pandemics have historically not been a major focus of research. The COVID‐19 pandemic has reinforced the need to understand pandemic causes and unequal consequences at multiple levels. Insights from past pandemics can strengthen the knowledge base and inform the study of current and future pandemics through an anthropological lens. In this paper, we discuss the distinctive social and epidemiological features of pandemics, as well as the ways in which biological anthropologists have previously studied infectious diseases, epidemics, and pandemics. We then review interdisciplinary research on three pandemics–1918 influenza, 2009 influenza, and COVID‐19–focusing on persistent social inequalities in morbidity and mortality related to sex and gender; race, ethnicity, and Indigeneity; and pre‐existing health and disability. Following this review of the current state of pandemic research on these topics, we conclude with a discussion of ways biological anthropologists can contribute to this field moving forward. Biological anthropologists can add rich historical and cross‐cultural depth to the study of pandemics, provide insights into the biosocial complexities of pandemics using the theory of syndemics, investigate the social and health impacts of stress and stigma, and address important methodological and ethical issues. As COVID‐19 is unlikely to be the last global pandemic, stronger involvement of biological anthropology in pandemic studies and public health policy and research is vital.

Racial and Ethnic Differences of Influenza-Associated Pediatric Hospitalizations and Deaths, 2008-2017

Background: Influenza is one of the most common causes of acute respiratory infections in children; its complications are a leading cause of morbidity and mortality. There is a paucity of pediatric data on influenza disparities among racial/ethnic minorities. Our study assesses if there are racial/ethnic differences in hospitalizations and mortality in children infected with influenza. Methods: This was a retrospective cohort study using the National Inpatient Sample (NIS) from January 1, 2008 to December 31, 2017. We included children 18 years and younger hospitalized with a primary or secondary diagnosis of influenza or its subtypes. We generated adjusted odds ratios (aORs) and 95% confidence intervals (CIs) to evaluate the associations between patient characteristics and influenza hospitalizations and influenza-related mortality. Results: There were 226,535 (0.04%) influenza-associated hospitalizations. When compared with non-Hispanic (NH) White children, minority children were more likely to be hospitalized with an influenza diagnosis [Hispanics (aOR = 1.25; 95% CI, 1.17 to 1.33), NH-Blacks (aOR = 1.21, 95% CI, 1.17 to 1.33) and NH-Others group (aOR = 1.11; 95% CI, 1.04 to 1.19)]. There was no racial/ethnic difference in mortality. Conclusions: Minority children experienced a higher likelihood of influenza-associated hospitalizations but not mortality. Further research is needed to reduce the racial/ethnic disparities of influenza's impact.

Estimated impact of maternal vaccination on global paediatric influenza-related in-hospital mortality: A retrospective case series

BACKGROUND

Influenza virus infection is an important cause of under-five mortality. Maternal vaccination protects children younger than 3 months of age from influenza infection. However, it is unknown to what extent paediatric influenza-related mortality may be prevented by a maternal vaccine since global age-stratified mortality data are lacking.

METHODS

We invited clinicians and researchers to share clinical and demographic characteristics from children younger than 5 years who died with laboratory-confirmed influenza infection between January 1, 1995 and March 31, 2020. We evaluated the potential impact of maternal vaccination by estimating the number of children younger than 3 months with in-hospital influenza-related death using published global mortality estimates.

FINDINGS

We included 314 children from 31 countries. Comorbidities were present in 166 (53%) children and 41 (13%) children were born prematurely. Median age at death was 8·6 (IQR 4·5-16·6), 11·5 (IQR 4·3-24·0), and 15·5 (IQR 7·4-27·0) months for children from low- and lower-middle-income countries (LMICs), upper-middle-income countries (UMICs), and high-income countries (HICs), respectively. The proportion of children younger than 3 months at time of death was 17% in LMICs, 12% in UMICs, and 7% in HICs. We estimated that 3339 annual influenza-related in-hospital deaths occur in the first 3 months of life globally.

INTERPRETATION

In our study, less than 20% of children is younger than 3 months at time of influenza-related death. Although maternal influenza vaccination may impact maternal and infant influenza disease burden, additional immunisation strategies are needed to prevent global influenza-related childhood mortality. The missing data, global coverage, and data quality in this study should be taken into consideration for further interpretation of the results.

FUNDING

Bill & Melinda Gates Foundation.

The coronavirus disease 2019 vaccine in pregnancy: risks, benefits, and recommendations

The coronavirus disease 2019 has caused over 2 million deaths worldwide, with over 412,000 deaths reported in Unites States. To date, at least 57,786 pregnant women in the United States have been infected, and 71 pregnant women have died. Although pregnant women are at higher risk of severe coronavirus disease 2019-related illness, clinical trials for the available vaccines excluded pregnant and lactating women. The safety and efficacy of the vaccines for pregnant women, the fetus, and the newborn remain unknown. A review of maternal and neonatal coronavirus disease 2019 morbidity and mortality data along with perinatal vaccine safety considerations are presented to assist providers with shared decision-making regarding vaccine administration for this group, including the healthcare worker who is pregnant, lactating, or considering pregnancy. The coronavirus disease 2019 vaccine should be offered to pregnant women after discussing the lack of safety data, with preferential administration for those at highest risk of severe infection, until safety and efficacy of these novel vaccines are validated.

Evaluation of manufacturing feasibility and safety of an MDCK cell-based live attenuated influenza vaccine (LAIV) platform

Cell culture based live attenuated influenza vaccines (LAIV) as an alternative to egg-based LAIV have been explored because of lack of easy access to SPF eggs for large scale production. In this study, feasibility of MDCK platform was assessed by including multiple LAIV strains covering both type A (H1 and H3) and type B seasonal strains as well as the candidate pandemic potential strains like A/H5 and A/H7 for the growth in MDCK cells. A risk assessment study was conducted on the cell banks to evaluate safety concerns related to tumorigenicity with a regulatory perspective. Tumorigenic potential of the MDCK cells was evaluated in nude mice (10⁷cells/mouse) model system. The 50% tumor producing dose (TPD₅₀) of MDCK cells was studied in SCID mice to determine the amount of cells required for induction of tumors. Further, we conducted an oncogenicity study in three sensitive rodent species as per the requirements specified in the WHO guidelines. We determined TPD₅₀ value of 1.9 X 10⁴ cells/mice through subcutaneous route. Our results suggest that, the intranasal route of administration of the cell culture based LAIV pose minimal to no risk of tumorigenicity associated with the host cells. Also, non-oncogenic nature of MDCK cells was demonstrated. Host cell DNA in the vaccine formulations was < 10 ng/dose which ensures vaccine safety. Production efficiency and consistency were characterized and the observed titer values of the viral harvest and the processed bulk were comparable to the expansion in embryonated eggs. The present study clearly establishes the suitability of MDCK cells as a substrate for the manufacture of a safe and viable LAIV.

The average peak time and intensity of seasonal influenza may vary by age: a study of laboratory confirmed influenza

Background

Seasonal influenza (SI) is an acute respiratory illness that exerts a severe impact on human life year-round. Yet, very few studies have been conducted to investigate its peak timing for different age groups.

Objective

To evaluate the average peak calendar time and intensity for the incidence of SI for different age groups.

Methods

The study uses laboratory-confirmed Influenza data from the Centers for Disease Control and Prevention (CDC) of the USA with age groups 2, 11, 34, 57 and 65 years during 2009-2018 for the analysis. A non-parametric method of estimation of a circular probability distribution called likelihood cross-validation method has been utilised.

Results

The average peak date of incidence for age groups 2 and 11 is around the last week of December. However, the date shifts to the last week of January to the first week of February for other groups. Age groups 65 and 2 years experienced the most severe impact among all.

Discussion

The average peak time for SI incidence is between the last week of December to January with a single peak time for every age group. However, the incidence seems to develop an additional moderate peak time for age group 65.

An Evolutionary Perspective of Virus Propagation

This paper presents an evolutionary algorithm that simulates simplified scenarios of the diffusion of an infectious disease within a given population. The proposed evolutionary epidemic diffusion (EED) computational model has a limited number of variables and parameters, but is still able to simulate a variety of configurations that have a good adherence to real-world cases. The use of two space distances and the calculation of spatial 2-dimensional entropy are also examined. Several simulations demonstrate the feasibility of the EED for testing distinct social, logistic and economy risks. The performance of the system dynamics is assessed by several variables and indices. The global information is efficiently condensed and visualized by means of multidimensional scaling.

Rare and extreme events: the case of COVID-19 pandemic

Complex systems have characteristics that give rise to the emergence of rare and extreme events. This paper addresses an example of such type of crisis, namely the spread of the new Coronavirus disease 2019 (COVID-19). The study deals with the statistical comparison and visualization of country-based real-data for the period December 31, 2019, up to April 12, 2020, and does not intend to address the medical treatment of the disease. Two distinct approaches are considered, the description of the number of infected people across time by means of heuristic models fitting the real-world data, and the comparison of countries based on hierarchical clustering and multidimensional scaling. The computational and mathematical modeling lead to the emergence of patterns, highlighting similarities and differences between the countries, pointing toward the main characteristics of the complex dynamics.

Age-Related Pathology Associated with H1N1 A/California/07/2009 Influenza Virus Infection

Influenza virus infection causes a spectrum of diseases, ranging from mild upper respiratory tract infection to severe lower respiratory tract infection, that can lead to diffuse alveolar damage, interstitial and airspace inflammation, or acute respiratory failure. Mechanisms instructing disease severity are not completely understood, but host, viral, and bacterial factors influence disease outcome. With age being one host factor associated with a higher risk of severe influenza, we investigated regional pulmonary distribution and severity of pneumonia after 2009 H1N1 influenza virus infection in newly weaned, adult, and aged ferrets to better understand age-dependent susceptibility and pathology. Aged ferrets exhibited greater weight loss and higher rates of mortality than adult ferrets, whereas most newly weaned ferrets did not lose weight but had a lack of weight gain. Newly weaned ferrets exhibited minimal pneumonia, whereas adult and aged ferrets had a spectrum of pneumonia severity. Influenza virus-induced pneumonia peaked earliest in adult ferrets, whereas aged ferrets had delayed presentation. Bronchial severity differed among groups, but bronchial pathology was comparable among all cohorts. Alveolar infection was strikingly different among groups. Newly weaned ferrets had little alveolar cell infection. Adult and aged ferrets had alveolar infection, but aged ferrets were unable to clear infection. These different age-related pneumonia and infection patterns suggest therapeutic strategies to treat influenza should be tailored contingent on age.

Pediatric influenza and illness severity: what is known and what questions remain?

PURPOSE OF REVIEW

Influenza causes a range of illnesses in children, from uncomplicated self-limited illness to severe disease and death. This review provides an update on the severity and burden of influenza in US children over recent seasons.

RECENT FINDINGS

The 2017-2018 influenza season was widespread and severe across all ages, including children. Disease severity is influenced by influenza virologic characteristics and host factors, as well as public health interventions such as influenza vaccination and antiviral treatment. In recent influenza A (H3N2)-predominant seasons (2016-2017 and 2017-2018), influenza vaccination effectiveness was higher in younger children compared with older children and adolescents, although the reasons for this are unclear. Interestingly, even in seasons when influenza A (H3N2) viruses predominate, influenza A (H1N1)pdm09 and B viruses can play a large role in severe pediatric disease. Although children less than 5 years of age and those with underlying medical conditions are at increased risk for severe disease, influenza-associated hospitalizations and deaths occur every season in healthy children.

SUMMARY

Influenza causes a substantial burden of outpatient visits, hospitalizations, and deaths among children. Ongoing research is important to better characterize factors that contribute to influenza severity, and to identify strategies to improve the impact of influenza vaccination and treatment.

Advancements in Nucleic Acid Based Therapeutics against Respiratory Viral Infections

Several viruses cause pulmonary infections due to their shared tropism with cells of the respiratory tract. These respiratory problems due to viral infection become a public health concern due to rapid transmission through air/aerosols or via direct-indirect contact with infected persons. In addition, the cross-species transmission causes alterations to viral genetic makeup thereby increasing the risk of emergence of pathogens with new and more potent infectivity. With the introduction of effective nucleic acid-based technologies, post translational gene silencing (PTGS) is being increasingly used to silence viral gene targets and has shown promising approach towards management of many viral infections. Since several host factors are also utilized by these viruses during various stages of infection, silencing these host factors can also serve as promising therapeutic tool. Several nucleic acid-based technologies such as short interfering RNAs (siRNA), antisense oligonucleotides, aptamers, deoxyribozymes (DNAzymes), and ribozymes have been studied and used against management of respiratory viruses. These therapeutic nucleic acids can be efficiently delivered through the airways. Studies have also shown efficacy of gene therapy in clinical trials against respiratory syncytial virus (RSV) as well as models of respiratory diseases including severe acute respiratory syndrome (SARS), measles and influenza. In this review, we have summarized some of the recent advancements made in the area of nucleic acid based therapeutics and highlighted the emerging roles of nucleic acids in the management of some of the severe respiratory viral infections. We have also focused on the methods of their delivery and associated challenges.

Nationwide Study on the Course of Influenza A (H1N1) Infections in Hospitalized Children in the Netherlands During the Pandemic 2009-2010

BACKGROUND

The influenza H1N1 pandemic of 2009-2010, provided a unique opportunity to assess the course of disease, as well as the analysis of risk factors for severe disease in hospitalized children (< 18 years).

METHODS

Retrospective national chart study on hospitalized children with H1N1 infection during the 2009-2010 pH1N1 outbreak.

RESULTS

Nine hundred forty patients (56% boys), median age 3.0 years, were enrolled; the majority were previously healthy. Treatment consisted of supplemental oxygen (24%), mechanical ventilation (5%) and antiviral therapy (63%). Fifteen patients died (1.6%), 5 of whom were previously healthy. Multivariable analyses confirmed pre-existent heart and lung disease as risk factors for intensive care unit admission. Risk factors for mortality included children with a neurologic or oncologic disease and psychomotor retardation.

CONCLUSIONS

This nationwide overview of hospitalized children confirms known risk groups for severe influenza infections. However, most of the acute and severe presentations of influenza occurred in previously healthy children.

Always ready, always prepared-preparing for the next pandemic

A future global pandemic is likely to occur and planning for the care of critically ill children is less robust than that for adults. This review covers the current state of federal and regional resources for pediatric care in pandemics, a strategy for pandemic preparation in pediatric intensive care units and regions focusing on stuff, space, staff and systems, considerations in developing surge capacity and triage protocols, special circumstances such as highly infectious and highly lethal pandemics, and a discussion of ethics in the setting of pediatric critical care in a pandemic.

Characteristics and Outcomes of Influenza-Associated Encephalopathy Cases Among Children and Adults in Japan, 2010-2015

Background

Influenza-associated encephalopathy (IAE) can result in severe neurologic disease with high mortality. Most IAE cases are reported among children worldwide. Understanding of IAE among adults is limited.

Methods

Data were collected on IAE cases reported through the National Epidemiological Surveillance of Infectious Diseases database in Japan from 2010 through 2015. IAE cases were stratified by age category and analyzed using descriptive statistics to assess differences in characteristics and outcomes.

Results

Among 385 IAE cases, median age at diagnosis was 7 years (range, 0-90), and 283 (74%) were aged <18 years. Mean seasonal incidence of IAE cases among children and adults (aged ≥18 years) was 2.83 and 0.19 cases per 1000000 population, respectively. IAE incidence did not vary by predominant influenza A virus subtype. IAE frequency was highest in school-aged (5-12 years) children (38%), followed by children aged 2-4 years (21%) and adults aged 18-49 years (11%). The proportion of cases with seizures was more common in children. There were more cases with cerebrospinal fluid pleocytosis among adults than in children (P < .01), especially among those aged 18-49 (17%) and 50-64 (19%) years. Case fatality proportion was highest in those aged 40-64 (17%) and ≥65 (20%) years.

Conclusions

We found differences in the clinical features of IAE between adults and children in Japan. Although IAE incidence was higher in children, mortality was higher in adults. Efforts are needed to prevent and improve survival of patients with IAE, especially in adults.

Influenza-Associated Pediatric Deaths in the United States, 2010-2016

BACKGROUND

Influenza-associated pediatric deaths became a notifiable condition in the United States in 2004.

METHODS

We analyzed deaths in children aged <18 years with laboratory-confirmed influenza virus infection reported to the Centers for Disease Control and Prevention during the 2010-2011 to 2015-2016 influenza seasons. Data were collected with a standard case report form that included demographics, medical conditions, and clinical diagnoses.

RESULTS

Overall, 675 deaths were reported. The median age was 6 years (interquartile range: 2-12). The average annual incidence was 0.15 per 100 000 children (95% confidence interval: 0.14-0.16) and was highest among children aged <6 months (incidence: 0.66; 95% confidence interval: 0.53-0.82), followed by children aged 6-23 months (incidence: 0.33; 95% confidence interval: 0.27-0.39). Only 31% (n = 149 of 477) of children aged ≥6 months had received any influenza vaccination. Overall, 65% (n = 410 of 628) of children died within 7 days after symptom onset. Half of the children (n = 327 of 654) had no preexisting medical conditions. Compared with children with preexisting medical conditions, children with none were younger (median: 5 vs 8 years old), less vaccinated (27% vs 36%), more likely to die before hospital admission (77% vs 48%), and had a shorter illness duration (4 vs 7 days; P < .05 for all).

CONCLUSIONS

Each year, influenza-associated pediatric deaths are reported. Young children have the highest death rates, especially infants aged <6 months. Increasing vaccination among children, pregnant women, and caregivers of infants may reduce influenza-associated pediatric deaths.

School practices to promote social distancing in K-12 schools: review of influenza pandemic policies and practices

BACKGROUND

During an evolving influenza pandemic, community mitigation strategies, such as social distancing, can slow down virus transmission in schools and surrounding communities. To date, research on school practices to promote social distancing in primary and secondary schools has focused on prolonged school closure, with little attention paid to the identification and feasibility of other more sustainable interventions. To develop a list and typology of school practices that have been proposed and/or implemented in an influenza pandemic and to uncover any barriers identified, lessons learned from their use, and documented impacts.

METHODS

We conducted a review of the peer-reviewed and grey literature on social distancing interventions in schools other than school closure. We also collected state government guidance documents directed to local education agencies or schools to assess state policies regarding social distancing. We collected standardized information from each document using an abstraction form and generated descriptive statistics on common plan elements.

RESULTS

The document review revealed limited literature on school practices to promote social distancing, as well as limited incorporation of school practices to promote social distancing into state government guidance documents. Among the 38 states that had guidance documents that met inclusion criteria, fewer than half (42%) mentioned a single school practice to promote social distancing, and none provided any substantive detail about the policies or practices needed to enact them. The most frequently identified school practices were cancelling or postponing after-school activities, canceling classes or activities with a high rate of mixing/contact that occur within the school day, and reducing mixing during transport.

CONCLUSION

Little information is available to schools to develop policies and procedures on social distancing. Additional research and guidance are needed to assess the feasibility and effectiveness of school practices to promote social distancing.

Characteristics and mortality risk of children with life-threatening influenza infection admitted to paediatric intensive care in England 2003-2015

BACKGROUND

Information is lacking about the severity of complications in children with influenza admitted to paediatric intensive care units (PICU) in the UK. In this study, we report risk factors for mortality, invasive ventilation and use of vasoactive drugs for children admitted to PICU with influenza.

METHODS

We evaluated all admissions to PICUs in England for resident children with a recorded influenza diagnosis between September 2003 and March 2015. We used the Paediatric Intensive Care Audit Network (PICANet) database linked to hospital admission records to identify influenza cases, and high-risk comorbidities among admitted children. We used mixed effects logistic regression models to determine risk factors for mortality, use of invasive ventilation and vasoactive drugs.

RESULTS

We identified 1961 influenza-related PICU admissions in 1778 children. Children with high-risk conditions accounted for 1540 admissions (78.5%). The odds of mortality were significantly higher for girls than boys (adjusted odds ratio 1.91; 95% confidence interval 1.31, 2.79), children from Asian/Asian British (2.70; 1.74, 4.20) or other minority ethnic groups (3.95; 1.65, 9.42) compared to white British children, and significantly increased before and during the A(H1N1)pdm 2009 pandemic compared to the post-pandemic period. Children required invasive ventilation in 1588 admissions (81.0%), and received vasoactive drugs in 586 admissions (29.9%).

CONCLUSIONS

Nearly four fifths of influenza-related PICU admissions occurred in children with high-risk conditions, highlighting the burden of severe influenza in this vulnerable population Further research is required to explain sex and ethnic group differences in PICU mortality among children admitted with influenza.

The emerging influenza virus threat: status and new prospects for its therapy and control

Influenza A viruses (IAVs) are zoonotic pathogens that cause yearly outbreaks with high rates of morbidity and fatality. The virus continuously acquires point mutations while circulating in several hosts, ranging from aquatic birds to mammals, including humans. The wide range of hosts provides influenza A viruses greater chances of genetic re-assortment, leading to the emergence of zoonotic strains and occasional pandemics that have a severe impact on human life. Four major influenza pandemics have been reported to date, and health authorities worldwide have shown tremendous progress in efforts to control epidemics and pandemics. Here, we primarily discuss the pathogenesis of influenza virus type A, its epidemiology, pandemic potential, current status of antiviral drugs and vaccines, and ways to effectively manage the disease during a crisis.

Influenza immunization policies: Which could be the main reasons for differences among countries?

Despite the availability of effective prophylactic and therapeutic measures, influenza remains one of the most important infectious disease threats to the human population. Every year, seasonal influenza epidemics infect up to 30% of the population; a relevant portion of the ill are hospitalized, and more than a marginal number die. In an attempt to reduce the medical, social and economic burden of influenza, vaccines are recommended by many health authorities worldwide. However, not all countries have a national program for influenza immunization. The main aim of this paper is to list the differences among influenza immunization policies of various countries, highlighting the most important scientific reasons that may have led health authorities to make different decisions. The manuscript highlights that national influenza immunization policies can vary significantly from country to country. These differences arise from insufficient evidence of the relevance of influenza infection from a clinical, social and economic point of view. The lack of precise data on the true frequency and clinical relevance of influenza infection makes it nearly impossible to establish the economic burden of influenza. Moreover, it remains very difficult to evaluate the efficacy of the different influenza vaccines and whether their use is cost-effective considering the various types of people receiving them and the indirect advantages. Disparities among countries will be overcome only when more reliable data regarding all these aspects of influenza infection, particularly those related to the true impact of the disease, are precisely defined.

Possible explanations for why some countries were harder hit by the pandemic influenza virus in 2009 - a global mortality impact modeling study

BACKGROUND

A global pandemic mortality study found prominent regional mortality variations in 2009 for Influenza A(H1N1)pdm09. Our study attempts to identify factors that explain why the pandemic mortality burden was high in some countries and low in others.

METHODS

As a starting point, we identified possible risk factors worth investigating for Influenza A(H1N1)pdm09 mortality through a targeted literature search. We then used a modeling procedure (data simulations and regression models) to identify factors that could explain differences in respiratory mortality due to Influenza A(H1N1)pdm09. We ran sixteen models to produce robust results and draw conclusions. In order to assess the role of each factor in explaining differences in excess pandemic mortality, we calculated the reduction in between country variance, which can be viewed as an effect-size for each factor.

RESULTS

The literature search identified 124 publications and 48 possible risk factors, of which we were able to identify 27 factors with appropriate global datasets. The modelling procedure indicated that age structure (explaining 40% of the mean between country variance), latitude (8%), influenza A and B viruses circulating during the pandemic (3-8%), influenza A and B viruses circulating during the preceding influenza season (2-6%), air pollution (pm10; 4%) and the prevalence of other infections (HIV and TB) (4-6%) were factors that explained differences in mortality around the world. Healthcare expenditure, levels of obesity, the distribution of antivirals, and air travel did not explain global pandemic mortality differences.

CONCLUSIONS

Our study found that countries with a large proportion of young persons had higher pandemic mortality rates in 2009. The co-circulation of influenza viruses during the pandemic and the circulation of influenza viruses during the preceding season were also associated with pandemic mortality rates. We found that real time assessments of 2009 pandemic mortality risk factors (e.g. obesity) probably led to a number of false positive findings.

Summary of Notifiable Infectious Diseases and Conditions - United States, 2015

The Summary of Notifiable Infectious Diseases and Conditions - United States, 2015 (hereafter referred to as the summary) contains the official statistics, in tabular and graphical form, for the reported occurrence of nationally notifiable infectious diseases and conditions in the United States for 2015. Unless otherwise noted, data are final totals for 2015 reported as of June 30, 2016. These statistics are collected and compiled from reports sent by U.S. state and territories, New York City, and District of Columbia health departments to the National Notifiable Diseases Surveillance System (NNDSS), which is operated by CDC in collaboration with the Council of State and Territorial Epidemiologists (CSTE). This summary is available at https://www.cdc.gov/MMWR/MMWR_nd/index.html. This site also includes summary publications from previous years.

Severe influenza in children: incidence and risk factors

INTRODUCTION

The identification of factors that can predispose to the development of severe influenza is essential to enable the implementation of optimal prevention and control measures for vulnerable populations.

AREAS COVERED

Unfortunately, data in the pediatric age group remain difficult to interpret. However, epidemiological data seem to suggest that the most severe influenza cases, those who are hospitalized, those who are admitted to the intensive care unit, and those who died, occur in children in the first 2 years of life and in school age patients. Expert commentary: Immaturity of the immune system, and in particular of the mechanisms that usually recognize influenza viruses and activate cytokine and chemokine responses to reduce viral replication, might explain the high hospitalization rate observed in the youngest patients. Some underlying chronic conditions favour the development of the severe cases, sometime leading to death, although both admission to the intensive care unit and death can occur in otherwise healthy subjects.

Community-Acquired Pneumonia Hospitalization among Children with Neurologic Disorders

OBJECTIVE

To describe and compare the clinical characteristics, outcomes, and etiology of pneumonia among children hospitalized with community-acquired pneumonia (CAP) with neurologic disorders, non-neurologic underlying conditions, and no underlying conditions.

STUDY DESIGN

Children <18 years old hospitalized with clinical and radiographic CAP were enrolled at 3 US children's hospitals. Neurologic disorders included cerebral palsy, developmental delay, Down syndrome, epilepsy, non-Down syndrome chromosomal abnormalities, and spinal cord abnormalities. We compared the epidemiology, etiology, and clinical outcomes of CAP in children with neurologic disorders with those with non-neurologic underlying conditions, and those with no underlying conditions using bivariate, age-stratified, and multivariate logistic regression analyses.

RESULTS

From January 2010-June 2012, 2358 children with radiographically confirmed CAP were enrolled; 280 (11.9%) had a neurologic disorder (52.1% of these individuals also had non-neurologic underlying conditions), 934 (39.6%) had non-neurologic underlying conditions only, and 1144 (48.5%) had no underlying conditions. Children with neurologic disorders were older and more likely to require intensive care unit (ICU) admission than children with non-neurologic underlying conditions and children with no underlying conditions; similar proportions were mechanically ventilated. In age-stratified analysis, children with neurologic disorders were less likely to have a pathogen detected than children with non-neurologic underlying conditions. In multivariate analysis, having a neurologic disorder was associated with ICU admission for children ≥2 years of age.

CONCLUSIONS

Children with neurologic disorders hospitalized with CAP were less likely to have a pathogen detected and more likely to be admitted to the ICU than children without neurologic disorders.

Novel pandemic influenza A (H1N1) and community-associated methicillin-resistant Staphylococcus aureus pneumonia

Postinfluenza bacterial pneumonia is a leading cause of influenza-associated death, and Staphylococcus aureus and Streptococcus pneumoniae have been important pathogens that have caused pneumonia since the influenza pandemic in 1919. Emergence of novel influenza A (H1N1) pdm09 and the concomitant global spread of community-associated methicillin-resistant S. aureus (CA-MRSA) have led to increasing prevalence of CA-MRSA pneumonia following influenza infection. Such an epidemiologic change poses a therapeutic challenge due to a high risk of inappropriate empiric antimicrobial therapy and poor clinical outcomes. Early diagnosis and initiation of appropriate antimicrobial therapy for post-influenza bacterial pneumonia have become even more important in the era of CA-MRSA. Therefore, novel molecular diagnostic techniques should be applied to more readily diagnose MRSA pneumonia.

Hospitalizations Attributable to Respiratory Infections among Children with Neurologic Disorders

OBJECTIVES

To characterize respiratory infection hospitalizations in children with neurologic disorders and to compare them with those of the general pediatric population.

STUDY DESIGN

We analyzed claims data from commercial insurance and Medicaid enrollees < 19 years of age from July 2006 to June 2011 who had ≥ 1 visit with an International Classification of Diseases, Ninth Revision, diagnosis code for a neurologic disorder. We identified hospitalizations with primary diagnosis codes indicating a respiratory infection and compared hospitalization rates with random samples of children from the commercial and Medicaid databases (comparison groups).

RESULTS

Among 33,651923 children, 255,046 (0.76%) had ≥ 1 neurologic condition. Among children with neurologic conditions, 8249 of 68,717 hospitalizations (12%) were attributed to a respiratory infection (rate: 21/1000 person-years), although rates varied by disorder. Children with neurologic disorders had greater rates than children in comparison groups (relative rate: Commercial Claims 7.4 [95% CI 7.1-7.7]; Medicaid 5.0 [95% CI 4.8-5.2]). Children < 2 years were most likely to be hospitalized, although those 10-18 years were 14.5 (95% CI 13.3-16.7) times more likely to be hospitalized than age-matched comparison groups. Co-occurring deafness, blindness, and scoliosis were associated with increased respiratory hospitalization rates.

CONCLUSIONS

Children with neurologic disorders are at 5- to 7-fold greater risk for hospitalization from respiratory infections compared with all children, although rates vary widely by disorder type, age, and comorbidities. Children with specific neurologic disorders and those who had co-occurring conditions have the highest rates.

Viral Infection in the Development and Progression of Pediatric Acute Respiratory Distress Syndrome

Viral infections are an important cause of pediatric acute respiratory distress syndrome (ARDS). Numerous viruses, including respiratory syncytial virus (RSV) and influenza A (H1N1) virus, have been implicated in the progression of pneumonia to ARDS; yet the incidence of progression is unknown. Despite acute and chronic morbidity associated with respiratory viral infections, particularly in "at risk" populations, treatment options are limited. Thus, with few exceptions, care is symptomatic. In addition, mortality rates for viral-related ARDS have yet to be determined. This review outlines what is known about ARDS secondary to viral infections including the epidemiology, the pathophysiology, and diagnosis. In addition, emerging treatment options to prevent infection, and to decrease disease burden will be outlined. We focused on RSV and influenza A (H1N1) viral-induced ARDS, as these are the most common viruses leading to pediatric ARDS, and have specific prophylactic and definitive treatment options.

A chest radiograph scoring system in patients with severe acute respiratory infection: a validation study

BACKGROUND

The term severe acute respiratory infection (SARI) encompasses a heterogeneous group of respiratory illnesses. Grading the severity of SARI is currently reliant on indirect disease severity measures such as respiratory and heart rate, and the need for oxygen or intensive care. With the lungs being the primary organ system involved in SARI, chest radiographs (CXRs) are potentially useful for describing disease severity. Our objective was to develop and validate a SARI CXR severity scoring system.

METHODS

We completed validation within an active SARI surveillance project, with SARI defined using the World Health Organization case definition of an acute respiratory infection with a history of fever, or measured fever of ≥ 38 °C; and cough; and with onset within the last 10 days; and requiring hospital admission. We randomly selected 250 SARI cases. Admission CXR findings were categorized as: 1 = normal; 2 = patchy atelectasis and/or hyperinflation and/or bronchial wall thickening; 3 = focal consolidation; 4 = multifocal consolidation; and 5 = diffuse alveolar changes. Initially, four radiologists scored CXRs independently. Subsequently, a pediatrician, physician, two residents, two medical students, and a research nurse independently scored CXR reports. Inter-observer reliability was determined using a weighted Kappa (κ) for comparisons between radiologists; radiologists and clinicians; and clinicians. Agreement was defined as moderate (κ > 0.4-0.6), good (κ > 0.6-0.8) and very good (κ > 0.8-1.0).

RESULTS

Agreement between the two pediatric radiologists was very good (κ = 0.83, 95% CI 0.65-1.00) and between the two adult radiologists was good (κ = 0.75, 95% CI 0.57-0. 93). Agreement of the clinicians with the radiologists was moderate-to-good (pediatrician:κ = 0.65; pediatric resident:κ = 0.69; physician:κ = 0.68; resident:κ = 0.67; research nurse:κ = 0.49, medical students: κ = 0.53 and κ = 0.56). Agreement between clinicians was good-to-very good (pediatrician vs. physician:κ = 0.85; vs. pediatric resident:κ = 0.81; vs. medicine resident:κ = 0.76; vs. research nurse:κ = 0.75; vs. medical students:κ = 0.63 and 0.66). Following review of discrepant CXR report scores by clinician pairs, κ values for radiologist-clinician agreement ranged from 0.59 to 0.70 and for clinician-clinician agreement from 0.97 to 0.99.

CONCLUSIONS

This five-point CXR scoring tool, suitable for use in poorly- and well-resourced settings and by clinicians of varying experience levels, reliably describes SARI severity. The resulting numerical data enables epidemiological comparisons of SARI severity between different countries and settings.

Burden of Influenza-Related Hospitalizations and Attributable Mortality in Pediatric Acute Lymphoblastic Leukemia

BACKGROUND

Influenza can be severe in patients with underlying malignancy; however, the rate of influenza hospitalizations and attributable mortality in children with cancer is unknown.

METHODS

We performed a retrospective cohort study among 10 698 children with new-onset acute lymphoblastic leukemia (ALL) from 41 US children's hospitals between January 1999 and September 2011. Influenza-related hospitalizations were identified using ICD-9 discharge diagnosis codes, excluding hospitalizations during low-prevalence influenza periods. Follow-up was censored at the earliest of 5 events: end of study period, expected end of chemotherapy, last known hospitalization, hematopoietic stem cell transplant, or death. Data were collected on hospitalization characteristics and resource utilization. Hospitalization rates were calculated using season-adjusted person-time. Crude attributable in-hospital mortality was calculated using baseline mortality for noninfluenza hospitalizations during the same period. Subgroup analysis was performed by time from ALL diagnosis and by age category.

RESULTS

The rate of influenza-related hospitalizations was 618.3 per 100 000 person-months. Rates were similar by time from ALL diagnosis and across age categories. Overall attributable in-hospital mortality was 1.0% (95% confidence interval [CI], 0.3%-2.3%) and was highest for children <6 months from diagnosis (1.6%; 95% CI, 0.4%-4.5%) and children <2 years of age (6.7%; 95% CI, 1.3%-22.7%). Total length of stay, days of broad-spectrum antibiotic exposure, and duration of intensive care were significantly greater for influenza-related hospitalizations compared with noninfluenza hospitalizations.

CONCLUSIONS

The burden of influenza-related hospitalizations in children with ALL is high and associated with significantly increased resource utilization and attributable mortality.

Hospitalised Malaysian children with pandemic (H1N1) 2009 influenza: clinical characteristics, risk factors for severe disease and comparison with the 2002-2007 seasonal influenza

INTRODUCTION

The pandemic caused by the H1N1 influenza virus in 2009 resulted in extensive morbidity and mortality worldwide. As the virus was a novel virus, there was limited data available on the clinical effects of the virus on children in Malaysia. Herein, we describe the clinical characteristics of children hospitalised with H1N1 influenza in a tertiary care centre; we also attempted to identify the risk factors associated with disease severity.

METHODS

In this retrospective study, we compared the characteristics of the children who were admitted into the University of Malaya Medical Centre, Malaysia, for H1N1 influenza during the pandemic with those who were admitted for seasonal influenza in 2002-2007.

RESULTS

Among the 77 children (aged ≤ 12 years) admitted to the centre due to H1N1 influenza from 1 July 2009-30 June 2010, nearly 60% were aged < 6 years and 40.3% had an underlying medical condition. The top three underlying medical conditions were bronchial asthma (14.3%), cardiac disease (10.4%) and neurological disorder (11.7%). The risk factors for severe disease were age < 2 years, underlying bronchial asthma and chronic lung disease. The three patients who died had a comorbid medical condition. The underlying cause of the deaths was acute respiratory distress syndrome or shock.

CONCLUSION

The clinical presentation of the children infected with the pandemic (H1N1) 2009 influenza virus did not differ significantly from that of children infected with seasonal influenza. However, there were more complaints of fever, cough and vomiting in the former group.

Intravenous peramivir inhibits viral replication, and leads to bacterial clearance and prevention of mortality during murine bacterial co-infection caused by influenza A(H1N1)pdm09 virus and Streptococcus pneumoniae

INTRODUCTION

Influenza virus infection increases susceptibility to bacterial infection and mortality in humans. Although the efficacy of approved intravenous peramivir, a neuraminidase (NA) inhibitor, against influenza virus infection has been reported, its efficacy against bacterial co-infection, which occurs during the period of viral shedding, was not fully investigated. To further understand the significance of treatment with peramivir, we assessed the efficacy of peramivir against a bacterial co-infection model in mice caused by clinically isolated influenza A(H1N1)pdm09 virus and Streptococcus pneumoniae.

METHODS

Mice were infected with influenza A(H1N1)pdm09. Peramivir was intravenously administered after the viral infection. At 2days post viral infection, the mice were infected with S. pneumoniae. Peramivir efficacy was measured by the survival rates and viral titers, bacterial titers, or proinflammatory cytokine concentrations in lung homogenates.

RESULTS

Peramivir treatment reduced the mortality of mice infected with influenza virus and S. pneumoniae. The survival rate in the peramivir-treated group was significantly higher than that in the oseltamivir-treated group. Viral titers and proinflammatory cytokine responses in the peramivir-treated group were significantly lower than those in the oseltamivir-treated group until at 2days post viral infection. Bacterial titer was significantly lower in the peramivir-treated group than in the oseltamivir-treated group at 4days post viral infection.

CONCLUSION

These results demonstrated that peramivir inhibits viral replication, consequently leading to bacterial clearance and prevention of mortality during severe murine bacterial co-infection, which occurs during the period of viral shedding, with the efficacy of peramivir being superior to that of oseltamivir.

Use of electronic death certificates for influenza death surveillance

Surveillance for influenza deaths has been used to gauge the severity of influenza seasons. Traditional surveillance, which relies on medical records review and laboratory testing, might not be sustainable during a pandemic. We examined whether electronic death certificates might provide a surveillance alternative. We compared information retrieved from electronic death certificates that listed influenza (or a synonym) with information retrieved from medical charts on which influenza deaths were reported by traditional means in Los Angeles County, California, USA, during the 2009 influenza A(H1N1) pandemic and 2 subsequent influenza seasons. Electronic death certificate surveillance provided timely information, matched the demographics and epidemiologic curve of that obtained from traditional influenza-related death surveillance, and had a moderately positive predictive value. However, risk factors were underreported on death certificates. Because surveillance by electronic death certificates does not require obtaining and reviewing medical records, it requires fewer resources and is less burdensome on public health staff.

Use of electronic death certificates for influenza death surveillance

These certificates might be useful during a pandemic, when resources for traditional surveillance are limited.

Surveillance for influenza deaths has been used to gauge the severity of influenza seasons. Traditional surveillance, which relies on medical records review and laboratory testing, might not be sustainable during a pandemic. We examined whether electronic death certificates might provide a surveillance alternative. We compared information retrieved from electronic death certificates that listed influenza (or a synonym) with information retrieved from medical charts on which influenza deaths were reported by traditional means in Los Angeles County, California, USA, during the 2009 influenza A(H1N1) pandemic and 2 subsequent influenza seasons. Electronic death certificate surveillance provided timely information, matched the demographics and epidemiologic curve of that obtained from traditional influenza-related death surveillance, and had a moderately positive predictive value. However, risk factors were underreported on death certificates. Because surveillance by electronic death certificates does not require obtaining and reviewing medical records, it requires fewer resources and is less burdensome on public health staff.

Influenza vaccination and treatment in children with neurologic disorders

Influenza viruses cause substantial morbidity in children each year, especially among children with specific chronic conditions. In particular, neurologic disorders have emerged as a strong risk factor for influenza-related complications. Children with these disorders may be vulnerable due to diminished respiratory muscle strength, decreased muscle tone or impaired mobility, which can compromise pulmonary function and the ability to handle secretions. Although they represent a small fraction of the general pediatric population, children with neurologic disorders make up a disproportionately high number of those children who are hospitalized and die as a result of influenza-associated complications. Annual 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, including children with neurologic disorders. Family members and those who work with these children in institutional, educational and daycare settings should also be vaccinated against influenza annually. However, there have been few studies of influenza vaccination specifically in this population. In addition, vaccine effectiveness may vary from year to year and vaccination will not prevent all infections. Early empiric antiviral treatment should be started promptly in these children if they present to healthcare providers with symptoms suspicious for influenza. This article reviews influenza epidemiology in children with neurologic disorders and what is known about vaccines and other methods of protecting this vulnerable population from influenza-related complications.

Burden of seasonal influenza in children with neurodevelopmental conditions

BACKGROUND

Studies have identified certain neurologic and neurodevelopmental conditions (NNC) as risk factors for severe influenza infection. The Canadian National Advisory Committee on Immunization does not currently recognize children with NNC as having a high risk of complicated influenza infection unless their condition compromises handling of respiratory secretions. We describe the burden of influenza in hospitalized children with NNC, focusing on those without potential airway compromise.

METHODS

Using multi-year surveillance data obtained by the Canadian Immunization Monitoring Program, Active (IMPACT), we examined presenting signs and symptoms, risk factors and outcomes of children hospitalized with seasonal influenza at 12 Canadian pediatric referral centers. Comparisons were made between children with various NNC and other medical conditions, with and without influenza vaccine indications. The analysis is descriptive with selected comparisons made among groups for important indicators of disease severity.

RESULTS

We identified 1991 children hospitalized with influenza over 5 seasons: 293 had NNC, 115 of whom did not have airway compromise or another vaccine indication. The latter group presented with seizures more frequently than those with NNC and a vaccine indication (41.7% vs. 26.4%; P = 0.006) and required intensive care unit admission (20.9% vs. 11.8%; P = 0.02) and mechanical ventilation (14.8% vs. 4.5%; P < 0.001) more often than children without NNC but with a vaccine indication.

CONCLUSIONS

The burden of influenza infection in children with NNC, even those whose conditions do not obviously compromise respiratory function, is significant. All children with NNC should be recognized as having a high risk of complicated influenza infection and be targeted to receive influenza immunization.

Influenza and parainfluenza viral infections in children

• On the basis of strong epidemiologic evidence, influenza and parainfluenza viruses are responsible for significant morbidity and mortality in young infants and children and in persons with chronic medical conditions. (1)(4)(26)(27)(35). • On the basis of research evidence, influenza vaccines are effective in preventing disease in high-risk individuals. (8)(17)(18). • On the basis of strong research evidence, influenza vaccines are safe in young infants and children 6 months or older. (8)(15).• On the basis of research evidence, the use of corticosteroids and epinephrine is beneficial in the treatment of laryngotracheitis caused by parainfluenza viruses. (44)(45)(46)(47). • Strong evidence supports the use of influenza vaccines in pregnant mothers as a strategy to prevent disease in infants younger than 6 months. (17)(18)(19).

Estimated paediatric mortality associated with influenza virus infections, United States, 2003–2010

Death certificate reports and laboratory-confirmed influenza deaths probably underestimate paediatric deaths attributable to influenza. Using US mortality data for persons aged <18 years who died during 28 September 2003 to 2 October 2010, we estimated influenza-attributable deaths using a generalized linear regression model based on seasonal covariates, influenza-certified deaths (deaths for which influenza was a reported cause of death), and occurrence during the 2009 pandemic period. Of 32 783 paediatric deaths in the death categories examined, 853 (3%) were influenza-certified. The estimated number of influenza-attributable deaths over the study period was 1·8 [95% confidence interval (CI) 1·3–2·8] times higher than the number of influenza-certified deaths. Influenza-attributable deaths were 2·1 (95% CI 1·5–3·4) times higher than influenza-certified deaths during the non-pandemic period and 1·1 (95% CI 1·0–1·8) times higher during the pandemic. Overall, US paediatric deaths attributable to influenza were almost twice the number reported by death certificate codes in the seasons prior to the 2009 pandemic.

Factors associated with receipt of 2009 pandemic influenza A (H1N1) monovalent and seasonal influenza vaccination among school-aged children: Maricopa County, Arizona, 2009-2010 influenza season

CONTEXT

To target school-aged children (SAC), who were identified as a priority for pandemic 2009 Influenza A (pH1N1) vaccination, Maricopa County (MC) initiated school-based influenza vaccination in 69% of its 706 schools during the 2009-2010 influenza season.

OBJECTIVE

To determine factors associated with receipt of pH1N1 monovalent and 2009-2010 seasonal influenza vaccination among SAC and evaluate the association of school-based vaccination with vaccination status of SAC.

DESIGN

Random-digit dialing was used to survey 600 MC households with willing adult participants and children grades K-12. Logistic regression was used to identify factors associated with pH1N1 and seasonal vaccine receipt.

SETTING

Arizona.

PARTICIPANTS

Household adults with children grades K-12.

MAIN OUTCOME MEASURE

Characteristics of children, parents, and households were obtained.

RESULTS

Among 909 SAC, 402 (44%) received pH1N1 and 436 (48%) received seasonal vaccination. Factors associated with pH1N1 vaccination included vaccine availability at school (adjusted odds ratio [AOR]: 1.6; 95% confidence interval [CI]: 1.0-2.7), high-risk medical condition in child (AOR: 2.4; 95% CI: 1.4-4.0), elementary versus high school attendance (AOR: 1.6; 95% CI: 1.0-2.7), and seasonal influenza vaccination (AOR: 10.0; 95% CI: 6.4-15.6). Factors associated with seasonal vaccination included Hispanic ethnicity (AOR: 2.2; 95% CI: 1.1-4.2), health insurance coverage (AOR: 4.8; 95% CI: 1.7-13.7), elementary versus high school attendance (AOR: 1.5; 95% CI: 1.0-2.5), and pH1N1 vaccination (AOR: 10.5; 95% CI: 6.7-16.6).

CONCLUSIONS

Availability of pH1N1 vaccine at school was independently associated with pH1N1 vaccination of MC school-aged children. School-based influenza vaccination campaigns should be considered to increase vaccination among this population.

Viral-bacterial interactions-therapeutic implications

Viral and bacterial respiratory tract infections are a leading cause of morbidity and mortality worldwide, despite the development of vaccines and potent antibiotics. Frequently, viruses and bacteria can co‐infect the same host, resulting in heightened pathology and severity of illness compared to single infections. Bacterial superinfections have been a significant cause of death during every influenza pandemic, including the 2009 H1N1 pandemic. This review will analyze the epidemiology and global impact of viral and bacterial co‐infections of the respiratory tract, with an emphasis on bacterial infections following influenza. We will next examine the mechanisms by which viral infections enhance the acquisition and severity of bacterial infections. Finally, we will discuss current management strategies for diagnosing and treating patients with suspected or confirmed viral‐bacterial infections of the respiratory tract. Further investigation into the interactions between viral and bacterial infections is necessary for developing new therapeutic approaches aimed at mitigating the severity of co‐infections.

Bacterial and viral infections associated with influenza

Influenza‐associated bacterial and viral infections are responsible for high levels of morbidity and death during pandemic and seasonal influenza episodes. A review was undertaken to assess and evaluate the incidence, epidemiology, aetiology, clinical importance and impact of bacterial and viral co‐infection and secondary infection associated with influenza. A review was carried out of published articles covering bacterial and viral infections associated with pandemic and seasonal influenza between 1918 and 2009 (and published through December 2011) to include both pulmonary and extra‐pulmonary infections. While pneumococcal infection remains the predominant cause of bacterial pneumonia, the review highlights the importance of other co‐ and secondary bacterial and viral infections associated with influenza, and the emergence of newly identified dual infections associated with the 2009 H1N1 pandemic strain. Severe influenza‐associated pneumonia is often bacterial and will necessitate antibiotic treatment. In addition to the well‐known bacterial causes, less common bacteria such as Legionella pneumophila may also be associated with influenza when new influenza strains emerge. This review should provide clinicians with an overview of the range of bacterial and viral co‐ or secondary infections that could present with influenza illness.

Demographic and clinical predictors of mortality from highly pathogenic avian influenza A (H5N1) virus infection: CART analysis of international cases

Background

Human infections with highly pathogenic avian influenza (HPAI) A (H5N1) viruses have occurred in 15 countries, with high mortality to date. Determining risk factors for morbidity and mortality from HPAI H5N1 can inform preventive and therapeutic interventions.

Methods

We included all cases of human HPAI H5N1 reported in World Health Organization Global Alert and Response updates and those identified through a systematic search of multiple databases (PubMed, Scopus, and Google Scholar), including articles in all languages. We abstracted predefined clinical and demographic predictors and mortality and used bivariate logistic regression analyses to examine the relationship of each candidate predictor with mortality. We developed and pruned a decision tree using nonparametric Classification and Regression Tree methods to create risk strata for mortality.

Findings

We identified 617 human cases of HPAI H5N1 occurring between December 1997 and April 2013. The median age of subjects was 18 years (interquartile range 6–29 years) and 54% were female. HPAI H5N1 case-fatality proportion was 59%. The final decision tree for mortality included age, country, per capita government health expenditure, and delay from symptom onset to hospitalization, with an area under the receiver operator characteristic (ROC) curve of 0.81 (95% CI: 0.76–0.86).

Interpretation

A model defined by four clinical and demographic predictors successfully estimated the probability of mortality from HPAI H5N1 illness. These parameters highlight the importance of early diagnosis and treatment and may enable early, targeted pharmaceutical therapy and supportive care for symptomatic patients with HPAI H5N1 virus infection.

Impact of 2009 pandemic influenza among Vietnamese children based on a population-based prospective surveillance from 2007 to 2011

Background

Influenza virus is one of the major viral pathogens causing pediatric acute respiratory infection (ARI). The spread of pandemic influenza A (A(H1N1)pdm09) in 2009 around the globe had a huge impact on global health.

Objective

To investigate the impact of A(H1N1)pdm09 on pediatric ARI in Vietnam.

Study design

An ongoing population-based prospective surveillance in central Vietnam was used. All children aged <15 years residing in Nha Trang city, enrolled to the ARI surveillance in Khanh Hoa General Hospital, from February 2007 through March 2011 were studied. Clinical data and nasopharyngeal swab samples were collected. Influenza A was detected and genotyped by multiplex polymerase chain reaction assays and sequencing.

Results

Among enrolled 2736 hospitalized ARI cases, 354 (13%) were positive for influenza A. Genotyping results revealed that seasonal H3N2 and H1N1 (sea-H1N1) viruses were cocirculating before A(H1N1)pdm09 appeared in July 2009. The A(H1N1)pdm09 replaced the sea-H1N1 after the pandemic. The majority of influenza A cases (90%) were aged <5 years with incidence rate of 537 (387–775) per 100 000 population. Annual incidence rates of hospitalized influenza cases for pre-, initial and post-pandemic periods among children aged <5 year were 474, 452, and 387 per 100 000, respectively. Children with A(H1N1)pdm09 were elder, visited the hospital earlier, less frequently had severe signs, and were less frequently associated with viral coinfection compared with seasonal influenza cases.

Conclusions

The A(H1N1)pdm09 did not increase the influenza annual hospitalization incidence or disease severity compared with seasonal influenza among pediatric ARI cases in central Vietnam.

The burden of seasonal and pandemic influenza in infants and children

The burden of influenza is unevenly distributed, with more severe outcomes in children aged <5 years than older children and adults. In spite of this, immunisation policies for young children are far from universal. This article provides an overview of the published evidence on the burden of influenza in children worldwide, with a particular interest in the impact of pandemic influenza in 2009-2010 (caused by the H1N1pdm09 virus). In an average season, up to 9.8 % of 0- to 14-year olds present with influenza, but incidence rates can be markedly higher in younger children. Children aged <5 years have greater rates of hospitalisation and complications than their older counterparts, particularly if the children have co-existing illnesses; historically, this age group have had higher mortality rates from the disease than other children, although during the 2009-2010 pandemic the median age of those who died of influenza was higher than in previous seasons. Admissions to hospital and emergency departments appear to have been more frequent in children with H1N1pdm09 infections than during previous seasonal epidemics, with pneumonia continuing to be a common complication in this setting. Outcomes in children hospitalised with severe disease also seem to have been worse for those infected with H1N1pdm09 viruses compared with seasonal viruses. Studies in children confirm that vaccination reduces the incidence of seasonal influenza and the associated burden, underlining the importance of targeting this group in national immunisation policies.

CONCLUSIONS

Children aged <5 years are especially vulnerable to influenza, particularly that caused by seasonal viruses, and vaccination in this group can be an effective strategy for reducing disease burden.

Influenza in hospitalized children in Ireland in the pandemic period and the 2010/2011 season: risk factors for paediatric intensive-care-unit admission

Influenza causes significant morbidity and mortality in children. This study's objectives were to describe influenza A(H1N1)pdm09 during the pandemic, to compare it with circulating influenza in 2010/2011, and to identify risk factors for severe influenza defined as requiring admission to a paediatric intensive care unit (PICU). Children hospitalized with influenza during the pandemic were older, and more likely to have received antiviral therapy than children hospitalized during the 2010/2011 season. In 2010/2011, only one child admitted to a PICU with underlying medical conditions had been vaccinated. The risk of severe illness in the pandemic was higher in females and those with underlying conditions. In 2010/2011, infection with influenza A(H1N1)pdm09 compared to other influenza viruses was a significant risk factor for severe disease. An incremental relationship was found between the number of underlying conditions and PICU admission. These findings highlight the importance of improving low vaccination uptake and increasing the use of antivirals in vulnerable children.

Immune dysfunction and bacterial coinfections following influenza

Secondary pulmonary infections by encapsulated bacteria including Streptococcus pneumoniae and Staphylococcus aureus following influenza represent a common and challenging clinical problem. The reasons for this polymicrobial synergy are still not completely understood, hampering development of effective prophylactic and therapeutic interventions. Although it has been commonly thought that viral-induced epithelial cell damage allows bacterial invasiveness, recent studies by several groups have now implicated dysfunctional innate immune defenses following influenza as the primary culprit for enhanced susceptibility to secondary bacterial infections. Understanding the immunological imbalances that are responsible for virus/bacteria synergy will ultimately allow the design of effective, broad-spectrum therapeutic approaches for prevention of enhanced susceptibility to these pathogens.

Influenza-associated pediatric deaths in the United States, 2004-2012

BACKGROUND

Influenza-associated deaths in children occur annually. We describe the epidemiology of influenza-associated pediatric deaths from the 2004-2005 through the 2011-2012 influenza seasons.

METHODS

Deaths in children <18 years of age with laboratory-confirmed influenza virus infection were reported to the Centers for Disease Control and Prevention by using a standard case report form to collect data on demographic characteristics, medical conditions, clinical course, and laboratory results. Characteristics of children with no high-risk medical conditions were compared with those of children with high-risk medical conditions.

RESULTS

From October 2004 through September 2012, 830 pediatric influenza-associated deaths were reported. The median age was 7 years (interquartile range: 1-12 years). Thirty-five percent of children died before hospital admission. Of 794 children with a known medical history, 43% had no high-risk medical conditions, 33% had neurologic disorders, and 12% had genetic or chromosomal disorders. Children without high-risk medical conditions were more likely to die before hospital admission (relative risk: 1.9; 95% confidence interval: 1.6-2.4) and within 3 days of symptom onset (relative risk: 1.6; 95% confidence interval: 1.3-2.0) than those with high-risk medical conditions.

CONCLUSIONS

Influenza can be fatal in children with and without high-risk medical conditions. These findings highlight the importance of recommendations that all children should receive annual influenza vaccination to prevent influenza, and children who are hospitalized, who have severe illness, or who are at high risk of complications (age <2 years or with medical conditions) should receive antiviral treatment as early as possible.