Admission diagnoses of children 0-16 years of age hospitalized with influenza

Management of influenza - updated Swedish guidelines for antiviral treatment

Influenza causes seasonal epidemics of respiratory infection in all parts of the world. Manifestations of influenza range from mild upper to severe lower respiratory tract infection. Medical risk groups are defined by factors predisposing for development of severe disease and are recommended annual vaccination as a protective measure. The previous Swedish treatment guidelines for influenza were issued in 2011, and a review of current evidence was deemed relevant. An important reason to revisit the guidelines is the recent approval of a novel drug for influenza treatment, baloxavir. Updated Swedish evidence-based guidelines created by a group of experts from various research areas, for the management of influenza are presented here. The work has been made in collaboration with the Public Health Agency of Sweden and the Swedish Reference Group for AntiViral therapy (RAV). The updated guidelines include guidelines for diagnostics, treatment and prophylaxis in special groups, including management of pregnant women and children with influenza. A new section about infection control has been added. Pharmacological treatment is covered in detail with regards to indication and dosage. Additionally, drug resistance and environmental aspects are discussed.

Trends and Changes in Influenza-associated Hospitalizations in Children During 25 Years in Finland, 1993-2018

BACKGROUND

Limited long-term data are available on potential changes in the demographics and management of children hospitalized with influenza.

METHODS

We identified all children ≤15 years old hospitalized with virologically confirmed influenza at Turku University Hospital, Finland, during the 25-year period of July 1993-June 2018. Data on clinical variables, comorbidities and management were retrieved directly from the medical records. Population-based rates of hospitalization were calculated using official annual databases of children living in the hospital catchment area.

RESULTS

Between 1993-1998 and 2013-2018, the median age of children increased from 1.3 years to 3.3 years ( P < 0.0001). The proportion of children <2 years of age decreased from 65.2% to 36.8%, whereas the proportion of children 6-15-year-old increased from 13.0% to 36.2% ( P < 0.0001 for both). The population-based rates of hospitalization decreased by 49% in children 1 year of age (incidence rate ratio, 0.51; 95% confidence interval: 0.27-0.92; P = 0.018) and increased by 194% in children 6-15 years old (incidence rate ratio, 2.94; 95% confidence interval: 1.70-5.32; P < 0.0001). The median duration of hospitalization shortened from 2.0 days (interquartile range [IQR], 1.0-4.0) to 1.0 day (IQR, 1.0-2.0; P < 0.0001).

CONCLUSIONS

During the 25 years, the median age of hospitalized children increased by 2 years, while the duration of hospitalization shortened.

Oseltamivir treatment of influenza A and B infections in infants

Background

Oseltamivir treatment is currently the only way of managing influenza in young infants for whom influenza vaccines are not licensed, but little data exist on the effectiveness of the treatment in this age group.

Methods

In a prospective study, we enrolled 431 newborn infants and followed them up for 10 months during their first respiratory season (September 2017‐June 2018). During each respiratory illness, we examined the infants and obtained nasopharyngeal specimens for determination of the viral etiology. Infants with influenza were re‐examined at short intervals, and additional nasopharyngeal specimens were obtained at each visit for measuring the viral load. All infants with symptoms <48 hours received oseltamivir treatment. The parents filled out daily symptom diaries.

Results

Among 23 infants with influenza A, the mean total duration of illness in oseltamivir recipients was 82.1 hours, compared with 253.5 hours in infants without treatment (P = .0003). For infants with influenza B, the corresponding durations were 110.0 and 173.9 hours, respectively (P = .03). In infants with influenza A, total symptom scores were significantly lower in oseltamivir‐treated infants at all time points between days 3 and 11 after the onset of therapy. In most children with either influenza A or B, viral antigen concentrations declined rapidly within 1‐2 days after the initiation of oseltamivir treatment.

Conclusions

Oseltamivir treatment of infants with influenza rapidly decreased the viral load in nasopharyngeal secretions and shortened the duration and severity of symptoms. The clinical effectiveness of oseltamivir appeared to be greater against influenza A than against influenza B infections.

Impact of Rapid Influenza Molecular Testing on Management in Pediatric Acute Care Settings

OBJECTIVES

To measure the impact of rapid influenza real-time qualitative reverse transcriptase polymerase chain reaction (RT-PCR) on patient management in busy pediatric emergency department (ED) and urgent care clinic settings.

STUDY DESIGN

We developed a brief, elective survey that clinicians completed when an influenza RT-PCR order was placed in the ED or urgent care clinic between February 18, 2019, and March 13, 2019. We captured the clinical suspicion for influenza, intended management plans, and actual management plans once influenza RT-PCR results were available.

RESULTS

We evaluated 339 encounters, of which 164 (48.4%) had a positive influenza RT-PCR. Clinical suspicion for influenza was a nonsignificant predictor for influenza PT-PCR positivity (P = .126). After rapid influenza RT-PCR results were available, clinicians changed their original plans in 44.5% of influenza RT-PCR positive vs 92.6% of influenza RT-PCR negative cases (P < .0001). Change in plans for antiviral use was observed in 26% of influenza positive vs 77% of influenza negative cases (P < .0001). A total of 135 antiviral prescriptions were avoided in patients with negative influenza RT-PCR.

CONCLUSIONS

Implementation of a rapid and accurate influenza RT-PCR in the acute care setting is important to systematically diagnose influenza in children and improve outpatient management decisions, because clinical suspicion for influenza is inaccurate. A negative influenza RT-PCR decreases unnecessary antiviral use and has the potential for significant cost savings.

Assessing the epidemiology and seasonality of influenza among children under two hospitalized in Amman, Jordan, 2010-2013

Background

The disease burden of influenza‐associated hospitalizations among children in Jordan is not well established. We aimed to characterize hospitalizations attributed to influenza in a pediatric population.

Methods

We conducted a cross‐sectional study from our viral surveillance cohort in children under 2 years hospitalized with acute respiratory symptoms and/or fever from March 2010 to March 2013. We collected demographic and clinical characteristics, and calculated the frequency of children who met the severe acute respiratory illness (SARI) criteria. Nasal specimens were tested using real‐time reverse transcriptase polymerase chain reaction to detect influenza A, B, or C. Further subtyping for influenza A‐positive isolates was conducted.

Results

Of the 3168 children enrolled in our study, 119 (4%) were influenza‐positive. Influenza types and subtypes varied by season but were predominantly detected between December and February. Codetection of multiple respiratory pathogens was identified in 58% of children with the majority occurring among those <6 months. Bronchopneumonia and rule‐out sepsis were the most common admission diagnoses, with influenza A accounting for over 2/3 of children with a rule‐out sepsis admission status. One‐third of children under 6 months compared to 3/4 of children 6‐23 months met the SARI criteria.

Conclusions

Influenza was an important cause of acute respiratory illness in children under 2 years. Children <6 months had the highest burden of influenza‐associated hospitalizations and were less likely to meet the SARI global surveillance case definition. Additional surveillance is needed in the Middle East to determine the true influenza burden on a global scale.

Burden of influenza during the first year of life

Background

Every year, influenza viruses infect millions of children and cause an enormous burden of disease. Young children are at the highest risk for influenza‐attributable hospitalizations. Nevertheless, most young children are treated as outpatients, and limited data are available on the burden of influenza in these children.

Methods

We carried out a prospective cohort study and followed 431 infants born in June‐August 2017 for 10 months from September 1, 2017, to June 30, 2018. The parents filled out daily symptom diaries and were instructed to bring their child for clinical examination at our study clinic each time the child had fever or any signs or symptoms of respiratory tract infection. During each visit, we obtained nasopharyngeal swab specimens for determination of the viral etiology of the illness.

Results

A total of 55 episodes of laboratory‐confirmed influenza were diagnosed among the 408 actively participating children, which corresponds to an annual incidence rate of 135/1000 children (95% Cl, 102‐175). Excluding five children with double viral infection, acute otitis media developed as a complication of influenza in 23 (46%) children. One (2%) child with influenza was hospitalized because of febrile convulsion. The effectiveness of influenza vaccination was 48% (95% CI, −29%‐80%).

Conclusions

The burden of influenza during the first year of life is heavy in the outpatient setting where most infants with influenza are managed. Effective strategies for the prevention of influenza particularly in infants under 6 months of age are needed to diminish the burden of disease in this age group.

Comparative Severity of Influenza A and B Infections in Hospitalized Children

BACKGROUND

Influenza A viruses are conventionally thought to cause more severe illnesses than B viruses, but few studies with long observation periods have compared the clinical severity of A and B infections in hospitalized children.

METHODS

We analyzed the clinical presentation, outcomes and management of all children <16 years of age admitted to Turku University Hospital, Finland, with virologically confirmed influenza A or B infection during the 14-year period of 1 July 2004 to 30 June 2018. All comparisons between influenza A and B were performed both within predefined age groups (0-2, 3-9 and 10-15 years) and in all age groups combined.

RESULTS

Among 391 children hospitalized with influenza A or B infection, influenza A was diagnosed in 279 (71.4%) and influenza B in 112 (28.6%) children. Overall, there were no significant differences in any clinical features or outcomes, management, treatment at intensive care unit or length of stay between children with influenza A and B, whether analyzed by age group or among all children. As indicators of the most severe clinical presentations, blood cultures were obtained from 101 (36.2%) children with influenza A and 39 (34.8%) with influenza B (P = 0.80), and lumbar puncture was performed to 16 (5.7%) children with influenza A and 11 (9.8%) children with influenza B (P = 0.15).

CONCLUSIONS

The clinical severity of influenza A and B infections is similar in children. For optimal protection against severe influenza illnesses, the use of quadrivalent vaccines containing both lineages of B viruses seems warranted in children.

Influenza virus seroincidence in a cohort of healthy and high-risk children enrolled in infancy, Bangkok, Thailand

BACKGROUND

We measured seroconversion to influenza viruses and incidence of symptomatic influenza virus infection in a cohort of children in Bangkok, Thailand.

METHODS

Children aged ≤6 months were followed for two years for acute respiratory illness (ARI) and had serum specimens taken at 6-month intervals and tested by hemagglutination inhibition (HI) assay. Seroconversion was defined as a >4-fold rise in the HI titers between time points with a titer of >40 in the second specimen. Respiratory swabs were tested by rRT-PCR for influenza. Data were analyzed using generalized linear models.

RESULTS

Of 350 children, 266 (76%, 147 were healthy and 119 were high-risk) had ≥2 serum specimens collected before influenza vaccination. During the 2-year follow-up, 266 children contributed 370 person-years of observation, excluding post-vaccination periods. We identified 32 ARI cases with rRT-PCR-confirmed influenza virus infection (7 infections/100 person-years, 95% confidence interval [CI], 4-11). There were 126 episodes of influenza virus infection, resulting in a seroconversion rate of 35 infections/100 person-years (95% CI, 30-42). Rates in healthy and high-risk children did not differ.

CONCLUSIONS

Influenza virus infection is common during the first two years of life among Thai children. A large proportion of infections may not be detected using the ARI case definition.

The burden of influenza-associated respiratory hospitalizations in Bhutan, 2015-2016

BACKGROUND

Influenza burden estimates help provide evidence to support influenza prevention and control programs. In this study, we estimated influenza-associated respiratory hospitalization rates in Bhutan, a country considering influenza vaccine introduction.

METHODS

Using real-time reverse transcription-polymerase chain reaction laboratory results from severe acute respiratory infection (SARI) surveillance, we estimated the proportion of respiratory hospitalizations attributable to influenza each month among patients aged <5, 5-49, and ≥50 years in six Bhutanese districts for 2015 and 2016. We divided the sum of the monthly influenza-attributed hospitalizations by the total of the six district populations to generate age-specific rates for each year.

RESULTS

In 2015, 10% of SARI patients tested positive for influenza (64/659) and 18% tested positive (129/736) in 2016. The incidence of influenza-associated hospitalizations among all age groups was 50/100 000 persons (95% confidence interval [CI]: 45-55) in 2015 and 118/100 000 persons (95% CI: 110-127) in 2016. The highest rates were among children <5 years: 182/100 000 (95% CI: 153-210) in 2015 and 532/100 000 (95% CI: 473-591) in 2016. The second highest influenza-associated hospitalization rates were among adults ≥50 years: 110/100 000 (95% CI: 91-130) in 2015 and 193/100 000 (95% CI: 165-221) in 2016.

CONCLUSIONS

Influenza viruses were associated with a substantial burden of severe illness requiring hospitalization especially among children and older adults. These findings can be used to understand the potential impact of seasonal influenza vaccination in these age groups.

Influenza burden, prevention, and treatment in asthma-A scoping review by the EAACI Influenza in asthma task force

To address uncertainties in the prevention and management of influenza in people with asthma, we performed a scoping review of the published literature on influenza burden; current vaccine recommendations; vaccination coverage; immunogenicity, efficacy, effectiveness, and safety of influenza vaccines; and the benefits of antiviral drugs in people with asthma. We found significant variation in the reported rates of influenza detection in individuals with acute asthma exacerbations making it unclear to what degree influenza causes exacerbations of underlying asthma. The strongest evidence of an association was seen in studies of children. Countries in the European Union currently recommend influenza vaccination of adults with asthma; however, coverage varied between regions. Coverage was lower among children with asthma. Limited data suggest that good seroprotection and seroconversion can be achieved in both children and adults with asthma and that vaccination confers a degree of protection against influenza illness and asthma-related morbidity to children with asthma. There were insufficient data to determine efficacy in adults. Overall, influenza vaccines appeared to be safe for people with asthma. We identify knowledge gaps and make recommendations on future research needs in relation to influenza in patients with asthma.

Prevention of influenza-related illness in young infants by maternal vaccination during pregnancy

The influenza virus circulates yearly and causes global epidemics. Influenza infection affects all age groups and causes mild to severe illness, and young infants are at particular risk for serious disease. The most effective measure to prevent influenza disease is vaccination; however, no vaccine is licensed for use in infants younger than 6 months old. Thus, there is a crucial need for other preventive strategies in this high-risk age group. Influenza vaccination during pregnancy protects both the mothers and the young infants against influenza infection. Vaccination during pregnancy boosts the maternal antibodies and increases the transfer of immunoglobulin G from the mother to the fetus through the placenta, which confers protection against infection in infants too young to be vaccinated. Data from clinical trials and observational studies did not demonstrate adverse effects to the mother, the fetus, or the infant after maternal influenza vaccination. We present the current data on the effectiveness and safety of influenza vaccination during pregnancy in preventing disease in the young infant.

Maternal influenza vaccine strategies in Kenya: Which approach would have the greatest impact on disease burden in pregnant women and young infants?

Background

Recent influenza surveillance data from Africa suggest an important burden of influenza-associated morbidity and mortality. In tropical countries where influenza virus transmission may not be confined to a single season alternative strategies for vaccine distribution via antenatal care (ANC) or semiannual campaigns should be considered.

Methods

Using data on monthly influenza disease burden in women of child-bearing age and infants aged 0–5 months in Kenya from 2010–2014, we estimated the number of outcomes (illnesses, medical visits, hospitalizations, and deaths) that occurred and that may have been averted through influenza vaccination of pregnant women using: 1) a year-round immunization strategy through ANC, 2) annual vaccination campaigns, and 3) semiannual vaccination campaigns.

Results

During 2010–2014, influenza resulted in an estimated 279,047 illnesses, 36,276 medical visits, 1612 hospitalizations and 243 deaths in pregnant women and 157,053 illnesses, 65,177 medical visits, 4197 hospitalizations, and 755 deaths in infants aged 0–5 months in Kenya. Depending on the mode of distribution and the vaccine coverage achieved, 12.8–31.4% of influenza-associated disease in pregnant women and 11.6–22.1% in infants aged 0–5 months might have been prevented through maternal influenza immunization. In this model, point estimates for influenza-associated disease averted through maternal vaccination delivered year-round in ANC or semiannually in campaigns were higher than vaccination delivered in a single annual campaign, but confidence intervals overlapped.

Conclusions

Vaccinating pregnant women against influenza can reduce the burden of influenza-associated illness, hospitalization and death in both pregnant women and their young infants. Alternative immunization strategies may avert more influenza-associated disease in countries where influenza virus transmission occurs throughout the year.

Influenza and respiratory syncytial virus in infants study (IRIS) of hospitalized and non-ill infants aged <1 year in four countries: study design and methods

Background

This multi-country prospective study of infants aged <1 year aims to assess the frequency of influenza virus and respiratory syncytial virus (RSV) infections associated with hospitalizations, to describe clinical features and antibody response to infection, and to examine predictors of very severe disease requiring intensive care.

Methods/Design

We are enrolling a hospital-based cohort and a sample of non-ill infants in four countries (Albania, Jordan, Nicaragua, and the Philippines) using a common protocol. We are currently starting year 2 of a 2- to 3-year study and will enroll approximately 3,000 infants hospitalized for any acute illness (respiratory or non-respiratory) during periods of local influenza and/or RSV circulation. After informed consent and within 24 h of admission, we collect blood and respiratory specimens and conduct an interview to assess socio-demographic characteristics, medical history, and symptoms of acute illness (onset ≤10 days). Vital signs, interventions, and medications are documented daily through medical record abstraction. A follow-up health assessment and collection of convalescent blood occurs 3-5 weeks after enrollment. Influenza and RSV infection is confirmed by singleplex real time reverse transcriptase polymerase chain reaction (rRT-PCR) assays. Serologic conversion will be assessed comparing acute and convalescent sera using hemagglutination inhibition assay for influenza antibodies and enzyme-linked immunosorbent assay (ELISA) for RSV. Concurrent with hospital-based enrollment, respiratory specimens are also being collected (and tested by rRT-PCR) from approximately 1,400 non-ill infants aged <1 year during routine medical or preventive care.

Discussion

The Influenza and RSV in Infants Study (IRIS) promises to expand our knowledge of the frequency, clinical features, and antibody profiles of serious influenza and RSV disease among infants aged <1 year, quantify the proportion of infections that may be missed by traditional surveillance, and inform decisions about the potential value of existing and new vaccines and other prevention and treatment strategies.

Clinical and socioeconomic impact of moderate-to-severe versus mild influenza in children

Some studies have assessed the efficacy of influenza vaccination in children separately for moderate-to-severe and any influenza, but the definition used for identifying children with moderate-to-severe illness has not been validated. We analyzed clinical and socioeconomic data from two prospective cohort studies of respiratory infections among children aged ≤13 years (four influenza seasons, 3,416 child-seasons of follow-up). We categorized children with laboratory-confirmed influenza into two mutually exclusive groups of moderate-to-severe and mild influenza using the previously proposed criteria. We obtained the data for the analyses from structured medical records filled out by the study physicians and from daily symptom cards filled out by the parents. Of 434 cases of influenza, 217 (50 %) were classified as moderate-to-severe and 217 (50 %) as mild. The mean duration of fever was 4.0 days in children with moderate-to-severe influenza and 3.1 days in those with milder illness (P < 0.0001). Antibiotics were prescribed to 111 (51 %) children with moderate-to-severe and to ten (5 %) children with mild influenza (P < 0.0001). The rates of parental work absenteeism were 184 days per 100 children with moderate-to-severe influenza and 135 days per 100 children with mild influenza (P = 0.02). The corresponding rates of children's own absenteeism from day care or school were 297 and 233 days respectively per 100 children (P = 0.006). Categorization of children into groups with moderate-to-severe and mild influenza is meaningful, and it identifies children in whom the clinical and socioeconomic impact of influenza is highest. Illness severity should be considered when assessing influenza vaccine effectiveness in children.

Influenza-associated outpatient visits among children less than 5 years of age in eastern China, 2011-2014

BACKGROUND

The disease burden of influenza in China has not been well described, especially among young children. The aim of this study was to estimate the incidence of outpatient visits associated with influenza in young children in Suzhou, a city of more than 11 million residents in Jiangsu Province in eastern China.

METHODS

Influenza-like illness (ILI) was defined as the presence of fever (axillary temperature ≥38 °C) and cough or sore throat. We collected throat swabs for children less than 5 years of age with ILI who visited Suzhou University Affiliated Children's Hospital (SCH) outpatient clinic or emergency room between April 2011 and March 2014. Suzhou CDC, a national influenza surveillance network laboratory, tested for influenza viruses by real-time reverse transcription-polymerase chain reaction assay (rRT-PCR). Influenza-associated ILI was defined as ILI with laboratory-confirmed influenza by rRT-PCR. To calculate the incidence of influenza-associated outpatient visits, we conducted community-based healthcare utilization surveys to determine the proportion of hospital catchment area residents who sought care at SCH.

RESULTS

The estimated incidence of influenza-associated ILI outpatient visits among children aged <5 years in the catchment area of Suzhou was, per 100 population, 17.4 (95 % CI 11.0-25.3) during April 2011-March 2012, 14.6 (95 % CI 5.2-26.2) during April 2012-March 2013 and 21.4 (95 % CI: 10.9-33.5) during April 2013-March 2014. The age-specific outpatient visit rates of influenza-associated ILI were 4.9, 21.1 and 21.2 per 100 children aged 0- <6 months, 6- <24 months and 24- <60 months, respectively.

CONCLUSION

Influenza virus infection causes a substantial burden of outpatient visits among young children in Suzhou, China. Targeted influenza prevention and control strategies for young children in Suzhou are needed to reduce influenza-associated outpatient visits in this age group.

Characterization of the Localized Immune Response in the Respiratory Tract of Ferrets following Infection with Influenza A and B Viruses

The burden of infection with seasonal influenza viruses is significant. Each year is typically characterized by the dominance of one (sub)type or lineage of influenza A or B virus, respectively. The incidence of disease varies annually, and while this may be attributed to a particular virus strain or subtype, the impacts of prior immunity, population differences, and variations in clinical assessment are also important. To improve our understanding of the impacts of seasonal influenza viruses, we directly compared clinical symptoms, virus shedding, and expression of cytokines, chemokines, and immune mediators in the upper respiratory tract (URT) of ferrets infected with contemporary A(H1N1)pdm09, A(H3N2), or influenza B virus. Gene expression in the lower respiratory tract (LRT) was also assessed. Clinical symptoms were minimal. Overall cytokine/chemokine profiles in the URT were consistent in pattern and magnitude between animals infected with influenza A and B viruses, and peak expression levels of interleukin-1α (IL-1α), IL-1β, IL-6, IL-12p40, alpha interferon (IFN-α), IFN-β, and tumor necrosis factor alpha (TNF-α) mRNAs correlated with peak levels of viral shedding. MCP1 and IFN-γ were expressed after the virus peak. Granzymes A and B and IL-10 reached peak expression as the virus was cleared and seroconversion was detected. Cytokine/chemokine gene expression in the LRT following A(H1N1)pdm09 virus infection reflected the observations seen for the URT but was delayed 2 or 3 days, as was virus replication. These data indicate that disease severities and localized immune responses following infection with seasonal influenza A and B viruses are similar, suggesting that other factors are likely to modulate the incidence and impact of seasonal influenza.

IMPORTANCE

Both influenza A and B viruses cocirculate in the human population, and annual influenza seasons are typically dominated by an influenza A virus subtype or an influenza B virus lineage. Surveillance data indicate that the burden of disease is higher in some seasons, yet it is unclear whether this is due to specific virus strains or to other factors, such as cross-reactive immunity or clinical definitions of influenza. We directly compared disease severities and localized inflammatory responses to different seasonal influenza virus strains, including the 2009 pandemic strain, in healthy naive ferrets. We found that the disease severities and the cytokine and chemokine responses were similar irrespective of the seasonal strain or the location of the infection in the respiratory tract. This suggests that factors other than the immune response to a particular virus (sub)type contribute to the variable impact of influenza virus infection in a population.

The Global Influenza Hospital Surveillance Network (GIHSN): a new platform to describe the epidemiology of severe influenza

BACKGROUND

Influenza is a global public health problem. However, severe influenza only recently has been addressed in routine surveillance.

OBJECTIVES

The Global Influenza Hospital Surveillance Network (GIHSN) was established to study the epidemiology of severe influenza in consecutive seasons in different countries. Our objective is to describe the GIHSN approach and methods.

METHODS

The GIHSN uses prospective active surveillance to identify consecutive influenza admissions in permanent residents of well-defined geographic areas in sites around the world. A core common protocol is followed. After consent, data are collected on patient characteristics and clinical outcomes, respiratory swabs are obtained, and the presence of influenza virus and subtype or lineage is ascertained by polymerase chain reaction. Data are collated and analyzed at the GIHSN coordination center.

RESULTS

The GIHSN has run its activities for two consecutive influenza seasons, 2012-2013 and 2013-2014, and hospitals in Brazil, China, France, Russian Federation, Turkey, and Spain have been involved in one or both seasons. Consistency on the application of the protocol and heterogeneity for the first season have been addressed in two previous publications. During both seasons, 19 677 eligible admissions were recorded; 11 843 (60%) were included and tested, and 2713 (23%) were positive for influenza: 991 (37%) A(H1N1); 807 (30%) A(H3N2); 583 (21%) B/Yamagata; 56 (2%) B/Victoria and 151 (6%) influenza A; and 125 (5%) influenza B were not characterized.

CONCLUSIONS

The GIHSN is a platform that provides information on severe influenza worldwide, applying a common core protocol and a consistent case definition.

Comparative Burden of Influenza A/H1N1, A/H3N2 and B Infections in Children Treated as Outpatients

BACKGROUND

Few studies have directly compared the clinical impact of different types and subtypes of influenza viruses in children.

METHODS

In a prospective study of respiratory infections in preenrolled cohorts of children ≤13 years of age, we compared the clinical features and the overall burden of illness between outpatient children with A/H1N1, A/H3N2 and B infections. The data were derived from structured medical records filled out by study physicians and from daily symptom diaries filled out by the parents throughout the follow-up period.

RESULTS

Of 358 children included in the analyses, 203 (57%) had influenza A/H1N1, 96 (27%) had A/H3N2, and 59 (16%) had influenza B infection. Children with influenza A/H3N2 were significantly younger (median, 3.2 years) than those with A/H1N1 (median, 4.8 years) or B (median, 5.1 years) infections (P < 0.0001). When adjusted for age, children 3-6 years of age with A/H3N2 infection had a higher frequency of fever ≥39.0°C (67% vs. 38%; P = 0.002), longer duration of fever (median, 4 vs. 3 days; P = 0.02) and more antibiotic treatments (43% vs. 20%; P = 0.004) than did children with A/H1N1 infections. Overall, the clinical presentation, duration of illness, frequency of complications, children's absenteeism from day care or school and parental work absenteeism were comparable between children with A/H1N1, A/H3N2 and B infections.

CONCLUSIONS

Adjusted for age, the clinical manifestations and the burden of illness are largely comparable between children with influenza A/H1N1, A/H3N2 and B infections.

The Unrecognized Burden of Influenza in Young Kenyan Children, 2008-2012

Influenza-associated disease burden among children in tropical sub-Saharan Africa is not well established, particularly outside of the 2009 pandemic period. We estimated the burden of influenza in children aged 0–4 years through population-based surveillance for influenza-like illness (ILI) and acute lower respiratory tract illness (ALRI). Household members meeting ILI or ALRI case definitions were referred to health facilities for evaluation and collection of nasopharyngeal and oropharyngeal swabs for influenza testing by real-time reverse transcription polymerase chain reaction. Estimates were adjusted for health-seeking behavior and those with ILI and ALRI who were not tested. During 2008–2012, there were 9,652 person-years of surveillance among children aged 0–4 years. The average adjusted rate of influenza-associated hospitalization was 4.3 (95% CI 3.0–6.0) per 1,000 person-years in children aged 0–4 years. Hospitalization rates were highest in the 0–5 month and 6–23 month age groups, at 7.6 (95% CI 3.2–18.2) and 8.4 (95% CI 5.4–13.0) per 1,000 person-years, respectively. The average adjusted rate of influenza-associated medically attended (inpatient or outpatient) ALRI in children aged 0–4 years was 17.4 (95% CI 14.2–19.7) per 1,000 person-years. Few children who had severe laboratory-confirmed influenza were clinically diagnosed with influenza by the treating clinician in the inpatient (0/33, 0%) or outpatient (1/109, 0.9%) settings. Influenza-associated hospitalization rates from 2008–2012 were 5–10 times higher than contemporaneous U.S. estimates. Many children with danger signs were not hospitalized; thus, influenza-associated severe disease rates in Kenyan children are likely higher than hospital-based estimates suggest.

The ESPID/ESWI Joint Symposium - A strong vote for universal influenza vaccination in children in Europe

During this year's 33rd annual meeting in Leipzig, Germany, the European Society of Paediatric Infectious Diseases (ESPID) jointly together with the European Scientific Working group on Influenza (ESWI), organized a staged debate on the motion of universal annual immunization of children against influenza as a cost-effective health intervention in Europe. Six invited speakers, all experts in the field of influenza vaccination, who were not necessary confident with their given position of pro or contra, battled each other with short oral presentations to convince the audience to vote for or against the motion.

Impact of influenza B lineage-level mismatch between trivalent seasonal influenza vaccines and circulating viruses, 1999-2012

BACKGROUND

Influenza B virus strains in trivalent influenza vaccines are frequently mismatched to the circulating B strains, but the population-level impact of such mismatches is unknown. We assessed the impact of vaccine mismatch on the epidemiology of influenza B during 12 recent seasonal outbreaks of influenza in Finland.

METHODS

We analyzed all available nationwide data on virologically confirmed influenza infections in all age groups in Finland between 1 July 1999 and 30 June 2012, with the exclusion of the pandemic season of 2009-2010. We derived data on influenza infections and the circulation of different lineages of B viruses during each season from the Infectious Diseases Register and the National Influenza Center, National Institute for Health and Welfare, Finland.

RESULTS

A total of 34 788 cases of influenza were recorded. Influenza A accounted for 74.0% and influenza B for 26.0% of all typed viruses. Throughout the 12 seasons, we estimated that 41.7% (3750 of 8993) of all influenza B infections were caused by viruses representing the other genetic lineage than the one in the vaccine. Altogether, opposite-lineage influenza B viruses accounted for 10.8% of all influenza infections in the population, the proportion being highest (16.8%) in children aged 10-14 years and lowest (2.6%) in persons aged ≥70 years.

CONCLUSIONS

The population-level impact of lineage-level mismatch between the vaccine and circulating strains of influenza B viruses is substantial, especially among children and adolescents. The results provide strong support for the inclusion of both influenza B lineages in seasonal influenza vaccines.

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.

Vaccination of healthy children against seasonal influenza: a European perspective

Despite ample evidence for the great burden that annual influenza epidemics place on children and society in general, few European countries currently recommend influenza vaccination of healthy children of any age. The most frequently cited reasons for reluctance to extend general vaccine recommendations to children include the view that influenza is a mild illness of limited clinical importance, lack of country-specific data on disease burden, uncertainty about the efficacy and safety of influenza vaccines in children and inadequate evidence of cost-effectiveness of vaccinating children. In recent years, several clinical studies have provided new and important information that help address many of these areas of question and concern. In light of this newly available scientific evidence, influenza vaccine recommendations for children should be properly reevaluated in all European countries. Furthermore, to allow for variation in costs and patterns of healthcare delivery between different countries, cost-effectiveness analyses of influenza vaccination of healthy children should be performed in each country or region. Finally, increased efforts should be made to educate both healthcare professionals and the great public about recent findings and advances in the field of pediatric influenza.

The impact of influenza and respiratory syncytial virus on hospitalizations for lower respiratory tract infections in young children: Slovenia, 2006-2011

Background

Influenza and respiratory syncytial viruses (RSV) are important viral pathogens in childhood.

Objectives

Our aim was to estimate the effect of influenza and RSV on excess hospitalizations for acute lower respiratory tract infections (ALRTI) in children aged ≤5.

Methods

Retrospective, population‐based study was performed for five seasons (2006–2011). Slovenian national hospital discharge data and surveillance data were used to estimate the effect of influenza and/or RSV on ALRTI hospitalizations (acute bronchiolitis, pneumonia, and acute bronchitis) using rate difference method.

Results

An excess was observed in average weekly ALRTI hospitalizations per 100 000 among children aged ≤5 in all five seasons during influenza and/or RSV active period. During three seasons, there was higher excess in ALRTI hospitalizations in the period when influenza/RSV cocirculated compared with the RSV period. In pandemic season (2009/2010), the only one without influenza/RSV overlap, excess hospitalization was higher in RSV period. The highest excess of hospitalizations was found among the youngest children (0‐5 months old). In all five seasons, acute bronchiolitis was the most common ALRTI recorded in hospitalized young children.

Conclusions

Respiratory syncytial viruses was leading viral pathogen associated with ALRTI hospitalizations in children aged ≤5. The cocirculation of influenza virus increased the burden of ALRTI hospitalizations especially in seasons with A(H3) predominance.

Comparison of the FilmArray Respiratory Panel and Prodesse real-time PCR assays for detection of respiratory pathogens

We compared the diagnostic performance and overall respiratory pathogen detection rate of the premarket version of the FilmArray Respiratory Panel (RP) multiplex PCR assay (Idaho Technology, Inc., Salt Lake City, UT) with those of the Food and Drug Administration (FDA)-cleared Prodesse ProFlu+, ProFAST+, ProParaflu+, Pro hMPV+, and ProAdeno+ real-time PCR assays (Gen-Probe, San Diego, CA). The assays were performed on a panel of 192 nasopharyngeal-secretion specimens collected from 81 children under 1 year of age with upper respiratory tract symptoms. To resolve discordant results and confirm pathogens detected only by the larger FilmArray panel, we performed laboratory-developed real-time PCR assays. Among viruses detectable by both commercial assays (adenovirus, human metapneumovirus, influenza A virus, influenza B virus, parainfluenza viruses 1 to 3, and respiratory syncytial virus), the FilmArray and Prodesse assays showed good overall agreement (181/192 [94.3%]; kappa = 0.87; 95% CI, 0.79 to 0.94). FilmArray RP detected more parainfluenza viruses 1 and 3 than ProParaflu+ (18 versus 13) while ProAdeno+ detected more adenoviruses (11 versus 6), but these differences were not statistically significant. Additionally, FilmArray RP detected 138 pathogens (confirmed as true positives) not included in the Prodesse assays (rhinovirus [RV]/enterovirus [EV], 118; bocavirus, 8; coronavirus, 7; parainfluenza virus 4, 4; Mycoplasma pneumoniae, 1). FilmArray RP was cleared by the FDA following the completion of this study. The FDA-cleared version includes the following targets: adenovirus, coronaviruses HKU1 and NL63, human metapneumovirus (hMPV), influenza A virus (to type level only), influenza A H1 seasonal virus, influenza A H3 seasonal virus, influenza A virus H1-2009, influenza B virus, parainfluenza viruses 1 to 4, respiratory syncytial virus (RSV), and RV/EV (no differentiation). The larger panel in the FilmArray RP assay allowed the detection of additional respiratory pathogens compared to the Prodesse assays. In this population of young children with upper respiratory tract infection, RV/EV accounted for the majority of the additional pathogens detected by FilmArray RP.