Burden of influenza in children: preliminary data from a pilot survey network on community diseases

Burden of influenza disease in children under 2 years of age hospitalized between 2011 and 2020 in France

BACKGROUND

Although influenza viruses cause significant morbidity and mortality worldwide, the impact of these infections on children in France and in other European countries has not been extensively characterized. The primary objective of the present study was to describe the burden of influenza disease on hospitalized children under 2 years of age in France, using data from the national hospital discharge summary database (Programme de Médicalisation des Systèmes d'Information, PMSI).

METHODS

In a retrospective study of hospital admissions for influenza among children under the age of 2 in France, we extracted and analyzed hospital administrative data from the PMSI database (from January 1, 2011, to December 31, 2020).

RESULTS

From 2011 to 2020, 28,507 children under the age of 2 were admitted to hospital with a primary or secondary diagnosis of influenza infection. The hospital admission rate was 205 per 100,000 for children under the age of 2, 276 per 100,000 for children under the age of 12 months, and 135 per 100,000 for children aged between 12 and 23 months. Children under 6 months of age were the most affected (45.4%). An underlying condition was identified for 9.4% of the children, and 2.2% of the children were admitted to the intensive care unit. The death rate was 0.12 per 100,000 for children under 2, 0.11 per 100,000 for children under 12 months, and 0.16 per 100,000 for children aged between 12 and 23 months.

CONCLUSIONS

In France, the burden of influenza disease is significant in children under the age of 2.

Molecular and biological characterization of influenza A viruses isolated from human fecal samples

Human influenza viruses are occasionally detected in the stools of influenza patients.

OBJECTIVES

Here, we investigated the molecular and biological characteristics of intestinal influenza viruses and their potential role in virus transmission.

METHODS

Fecal samples were first screened for the presence of influenza viral RNA using RT-qPCR. Positive fecal samples were subjected to cell culture. Isolated viruses were then sequenced using MiSeq platform. Replication kinetics and receptor binding affinity were also evaluated.

RESULTS

Influenza RNA was detected in stool samples of 41% (36/87) of influenza A positive patients. Among the 36 stool samples subjected to viral isolation, 5 showed virus growth. Sequence analysis of isolated viruses revealed two distinct mutation patterns in fecal viruses. Set I viruses was able to replicate to higher titers in cell culture despite the limited number of mutations (6 mutations) compared to set II viruses (>10 mutations). Functional analysis of both sets revealed the ability to replicate efficiently in differentiated human bronchial cells. Receptor binding testing has also demonstrated their ability to bind α 2,3 and α 2,6 sialic acid receptors.

CONCLUSION

The ability of fecal influenza viruses to replicate in intestinal cells and human 3D bronchial cells might suggest their possible contribution in virus transmission.

Molecular Epidemiology and Vaccine Compatibility Analysis of Seasonal Influenza Viruses in Wuhan, 2016-2019

Influenza viruses (FLUV) cause high morbidity and mortality annually in the world and pose a serious threat to the public health. Wuhan, as an important transportation hub in China, has a dense population and suitable climate, which also lays a major hidden danger for the outbreak of influenza. To survey and characterize the seasonal FLUV in Wuhan during 2016-2019, we collected 44,738 throat swabs, among which 15.5% were influenza A (FLUAV) positive, 6.1% influenza B (FLUBV) and 0.3% co-infection. By monitoring FLUV in each month from June 2016 to May 2019, different with the previously seasonality pattern, only a single influenza peak was appeared in winter of 2017-2018 and 2018-2019, respectively. These data indicated that the complex circulation pattern of seasonal influenza in Wuhan. In addition, we found the age group was skewed towards 5-14 years group whose activity were mostly school based, which suggested school may be an important place for influenza outbreaks. Meanwhile, phylogenic analysis revealed that two subtypes (subclade 3C.2a2 and 3C.2a1b) of A(H3N2) were circulating in Wuhan and there was an obvious transition in 2018 because the two subclades were detected simultaneously. Furthermore, by estimating the vaccine effectiveness, we found that the vaccine strain of FLUAV didn't seem to match very well the current epidemic strain, especially A(H3N2). Hence, more accurate prediction of seasonal outbreak is essential for vaccine design. Taken together, our results provided the current information about seasonal FLUV in Wuhan which form the basis for vaccine updating.

Risk factors for seasonal influenza virus detection in stools of patients consulting in general practice for acute respiratory infections in France, 2014-2016

Background

Previous studies reported detection of influenza RNA in stools of patients with seasonal influenza infection. While this detection may have a clinical significance, other factors may influence the stool positivity for influenza viruses.

Objectives

The objective of this study was to investigate demographical, clinical, and microbiological factors which could favor the presence of influenza viral RNA in the stools of patients with laboratory‐confirmed influenza infection.

Methods

Acute respiratory infection (ARI) patients were enrolled by general practitioners (GP) during two winter seasons (2014‐2016). Nasopharyngeal swabs, stool specimens, and clinical data were collected. Samples were tested for 12 respiratory pathogen groups (nasopharyngeal and stool specimens) and for 12 enteric pathogens (stool specimens).

Results

Among the 331 patients with ARI enrolled by GP, 114 (34.4%) presented influenza infection. Influenza RNA was detected in stool samples of 21% (24/114) of the 114 stool specimens analyzed. Hospitalization (adjusted odds ratio (aOR) = 7.8 (95% confidence interval (CI)) [1.7‐33.7], P = .02), age between 45 and 64 years (aOR = 4.8 [1.7‐14.5], P = .01), consumption of raw shellfish and/or mollusks (aOR = 16.7 [3.6‐90.9], P = .00), and use of antibiotics (aOR = 6.4 [2.1‐19.8], P = .006) or antiviral treatment (aOR = 7.4 [1.9‐29], P = .01) were significantly associated with an increased odds of the detection of influenza RNA in stools. Among the 24 stool samples subjected to viral isolation, no one showed virus growth.

Conclusions

These findings will be useful to studies investigating the dissemination route of influenza viruses to gastrointestinal tract.

Prevalence of gastrointestinal symptoms in patients with influenza, clinical significance, and pathophysiology of human influenza viruses in faecal samples: what do we know?

This review provides for the first time an assessment of the current understanding about the occurrence and the clinical significance of gastrointestinal (GI) symptoms in influenza patients, and their correlation with the presence of human influenza viruses in stools of patients with confirmed influenza virus infection. Studies exploring how human influenza viruses spread to the patient’s GI tract after a primary respiratory infection have been summarized. We conducted a systematic search of published peer-reviewed literature up to June 2015 with regard to the above-mentioned aspects, focusing on human influenza viruses (A(H1N1), A(H1N1)pdm09, A(H3N2), and B). Forty-four studies were included in this systematic review and meta-analysis. The pooled prevalence of any digestive symptoms ranged from 30.9 % (95 % CI, 9.8 to 57.5; I² = 97.5 %) for A(H1N1)pdm09 to 2.8 % (95 % CI, 0.6 to 6.5; I² = 75.4 %) for A(H1N1). The pooled prevalence of influenza viruses in stool was 20.6 % (95 % CI, 8.9 to 35.5; I² = 96.8 %), but their correlation with GI symptoms has rarely been explored. The presence of viral RNA in stools because of haematogenous dissemination to organs via infected lymphocytes is likely, but the potential to cause direct intestinal infection and faecal–oral transmission warrants further investigation. This review highlights the gaps in our knowledge, and the high degree of uncertainty about the prevalence and significance of GI symptoms in patients with influenza and their correlation with viral RNA positivity in stool because of the high level of heterogeneity among studies.

Immunogenicity of a quadrivalent Ann Arbor strain live attenuated influenza vaccine delivered using a blow-fill-seal device in adults: a randomized, active-controlled study*

BACKGROUND

Influenza B strains from two distinct lineages (Yamagata and Victoria) have cocirculated over recent years. Current seasonal vaccines contain a single B lineage resulting in frequent mismatches between the vaccine strain and the circulating strain. An Ann Arbor strain quadrivalent live attenuated influenza vaccine (Q/LAIV) containing B strains from both lineages is being developed to address this issue.

OBJECTIVES

The goal of this study was to evaluate whether Q/LAIV administered intranasally as a single dose to a single nostril, using a blow-fill-seal (BFS) delivery system had a similar immunogenicity and safety profile compared with the licensed trivalent vaccine delivered using the Accuspray device.

PATIENTS/METHODS

Adults aged 18-49 years were randomized to receive one intranasal dose of Q/LAIV delivered using a BFS device (Q/LAIV-BFS; n=1202) or one of two trivalent live attenuated influenza vaccines (T/LAIV) containing one of the corresponding B strains (total T/LAIV, n=598). Primary endpoints were the post-vaccination strain-specific serum hemagglutination inhibition antibody geometric mean titers for each strain. Secondary immunogenicity endpoints, safety, and acceptability of the BFS device were also assessed.

RESULTS

Q/LAIV was immunogenically non-inferior to T/LAIV for all four influenza strains. Secondary immunogenicity outcomes were consistent with the primary endpoint. Solicited symptoms and AEs were comparable in both groups. Subjects considered the BFS device to be acceptable.

CONCLUSIONS

Immune responses to vaccination with Ann Arbor strain Q/LAIV-BFS were non-inferior to those with T/LAIV. Q/LAIV may confer broader protection against seasonal influenza B by targeting both major influenza B lineages.

The migration of T cells in response to influenza virus is altered in neonatal mice

Influenza virus is a significant cause of mortality and morbidity in children; however, little is known about the T cell response in infant lungs. Neonatal mice are highly vulnerable to influenza and only control very low doses of virus. We compared the T cell response to influenza virus infection between mice infected as adults or at 2 d old and observed defective migration into the lungs of the neonatal mice. In the adult mice, the numbers of T cells in the lung interstitia peaked at 10 d postinfection, whereas neonatal T cell infiltration, activation, and expression of TNF-alpha was delayed until 2 wk postinfection. Although T cell numbers ultimately reached adult levels in the interstitia, they were not detected in the alveoli of neonatal lungs. Instead, the alveoli contained eosinophils and neutrophils. This altered infiltrate was consistent with reduced or delayed expression of type 1 cytokines in the neonatal lung and differential chemokine expression. In influenza-infected neonates, CXCL2, CCL5, and CCL3 were expressed at adult levels, whereas the chemokines CXCL1, CXCL9, and CCL2 remained at baseline levels, and CCL11 was highly elevated. Intranasal administration of CCL2, IFN-gamma, or CXCL9 was unable to draw the neonatal T cells into the airways. Together, these data suggest that the T cell response to influenza virus is qualitatively different in neonatal mice and may contribute to an increased morbidity.

[Diagnostic yield of paediatric respiratory samples in the Balearic Islands Sentinel Influenza Surveillance Network]

INTRODUCTION

Influenza disease is subjected to surveillance by national networks (RC) that predict the epidemic behaviour by reporting clinical and virological data.

OBJECTIVES

To evaluate the effectiveness of the paediatric respiratory samples in the Balearic Islands RC in the last five epidemic seasons.

MATERIAL AND PATIENTS

A breath sample was taken from paediatric patients in the RC who had flu symptoms. The samples were inoculated in the MDCK cell line. We reviewed the epidemiological data of patients with a culture positive to influenza A and B.

RESULTS

A total of 338 pharyngeal swabs from the RC were analysed during the study period. Of these, 65 (19.3%) belonged to <14 years old patients, and 44.6% of the samples were positive as opposed to 39.1% of adult respiratory samples. The influenza A virus was isolated in 24 paediatric samples (82.7%) and the influenza B virus in 5 (17.3%). The mean age of the paediatric patients of the RC who were positive was 8.5 years. Only 3 patients in the 0-4 year old group were positive (10.3%) and 26 patients (89.7%) in the 5-14 years old group.

CONCLUSIONS

In spite that paediatricians represented only 22% of the RC doctors and obtain the 19.3% of all respiratory samples, the percentage and effectiveness of these is higher that that obtained in the adult population.

Influenza A and respiratory syncytial virus hospital burden in young children in East London

Epidemiological studies have demonstrated high hospitalization rates attributable to influenza and RSV in children aged 6 months and those aged <12 months, respectively (43 and 92.5/10 000 person-months, respectively). In conclusion, these high paediatric RSV and influenza incidence rates can be used to inform UK policy on childhood influenza immunization and subsequent RSV immunization in the future.

Safety, efficacy, and effectiveness of cold-adapted influenza vaccine-trivalent against community-acquired, culture-confirmed influenza in young children attending day care

OBJECTIVE

The goal was to evaluate the safety, tolerability, and efficacy of an investigational, refrigerator-stable formulation of live attenuated influenza vaccine (cold-adapted influenza vaccine-trivalent) against culture-confirmed influenza, acute otitis media, and effectiveness outcomes in young children in day care over 2 consecutive influenza seasons.

METHODS

Children 6 to <36 months of age who were attending day care were assigned randomly in year 1 to receive 2 doses of vaccine or placebo intranasally, 35 +/- 7 days apart. In year 2, subjects received 1 dose of the same treatment as in year 1.

RESULTS

A total of 1616 subjects (vaccine: 951 subjects; placebo: 665 subjects) in year 1 and 1090 subjects (vaccine: 640 subjects; placebo: 450 subjects) in year 2 were able to be evaluated for efficacy. The mean age at first vaccination was 23.4 +/- 7.9 months. In year 1, the overall efficacy of the vaccine against influenza subtypes similar to the vaccine was 85.4%; efficacy was 91.8% against A/H1N1 and 72.6% against B. In year 2, the overall efficacy was 88.7%; efficacy was 90.0% against H1N1, 90.3% against A/H3N2, and 81.7% against B. Efficacy against all episodes of acute otitis media associated with culture-confirmed influenza was 90.6% in year 1 and 97.0% in year 2. Runny nose or nasal discharge after dose 1 in year 1 was the only reactogenicity event that was significantly more frequent with cold-adapted influenza vaccine-trivalent (82.3%) than placebo (75.4%).

CONCLUSIONS

Cold-adapted influenza vaccine-trivalent was well tolerated and effective in preventing culture-confirmed influenza illness in children as young as 6 months of age who attended day care.

Influenza-related hospitalizations in children younger than three years of age

BACKGROUND

To determine the rates of influenza-related hospitalization and to know the clinical manifestations and underlying diseases in children younger than 3 years who are hospitalized with influenza.

METHODS

Retrospective, descriptive study (1996-2003), performed in a tertiary teaching hospital in Madrid. Data of hospitalized children, younger than 3 years, with influenza virus isolation from nasal aspirates were collected. Rates of hospitalization for every year were calculated.

RESULTS

Overall, 146 children hospitalized with influenza were identified: 117 had community-acquired influenza as the only disease, 18 had community-acquired influenza and were coinfected with other pathogens, and 11 had nosocomial infection. Rates of influenza hospitalization for years 1996, 1997, 1998, 1999, 2000, 2001, 2002, and 2003 were 0.42, 0.11, 1.46, 1.54, 0.53, 0.25, 0.19, and 0.82, respectively, per 1000 children younger than 3 years of age. Children <or=1 year of age accounted for almost two thirds of admissions. Bronchitis/bronchiolitis (42 children), pneumonia (11 children), fever without source (36 children), and suspected sepsis (9 children) accounted for almost 90% of all hospitalizations in children with community-acquired influenza.Forty-seven patients (40%) had underlying diseases, mainly chronic pulmonary disease and congenital heart disease. Ten patients (8.5%) with community-acquired influenza A and underlying conditions were admitted to the intensive care unit.

CONCLUSIONS

Influenza is an important cause of hospitalization in young children. The use of influenza vaccine in high-risk children could prevent hospitalizations and cases of influenza-related diseases.

Estimating influenza hospitalizations among children

Two surveillance systems gave a better estimate of influenza hospitalizations in children <5 years of age than either system alone.

Although influenza causes more hospitalizations and deaths among American children than any other vaccine-preventable disease, deriving accurate population-based estimates of disease impact is challenging. Using 2 independent surveillance systems, we performed a capture-recapture analysis to estimate influenza-associated hospitalizations in children in Davidson County, Tennessee, during the 2003–2004 influenza season. The New Vaccine Surveillance Network (NVSN) enrolled children hospitalized with respiratory symptoms or fever and tested them for influenza. The Tennessee Emerging Infections Program (EIP) identified inpatients with positive influenza diagnostic test results through review of laboratory and infection control logs. The hospitalization rate estimated from the capture-recapture analysis in children <5 years of age was 2.4 per 1,000 (95% confidence interval 1.8–3.8). When NVSN estimates were compared with capture-recapture estimates, NVSN found 84% of community-acquired cases, EIP found 64% of cases in which an influenza rapid test was performed, and the overall sensitivity of NVSN and EIP for influenza hospitalizations was 73% and 38%, respectively.

Infecciones por virus de la gripe en menores de dos años

INTRODUCTION

Influenza is a major cause of respiratory tract illness in infants. The clinical characteristics of these infections are non-specific and the burden of influenza is frequently underestimated in very young children. The objective of this study was to describe confirmed influenza infections in infants < 2 years attended in a level II public hospital. A second-rate aim was to compare influenza infections in hospitalized infants with respiratory syncytial virus (VRS) infection in the same population.

PATIENTS AND METHODS

We performed a descriptive, prospective study between 1991 and 2003 in infants younger than 24 months of age, who were admitted to the Severo Ochoa Hospital (Leganés. Madrid) with fever or respiratory tract infection. Virological diagnosis was made with direct immunofluorescent assay and/or reverse transcription-polymerase chain reaction on specimens obtained from nasopharyngeal washings. The patients' clinical characteristics were recorded. Patients with influenza infection were compared with a similar group of infants with RSV infection.

RESULTS

We analyzed hospitalized 100 infants with influenza infection. Influenza caused 4.1% of the admissions in infants with fever or respiratory tract infection. Influenza A was isolated in 83%, influenza B in 12% and influenza C in 5% of the patients. The mean age of hospitalized infants was 8.3 +/- 5.9 months and the most frequent clinical diagnoses were bronchiolitis in 38%, recurrent wheezing in 25%, upper respiratory tract infection in 19% and pneumonia in 9%. Fever > 38 degrees C was present in 83% of the patients. Radiologic infiltrate was found in 65% of the children. Oxygen saturation less then 95% was present in 44%. In children under 6 months of age fever was less frequent (p = 0.049) and upper respiratory tract infection was more frequent (p = 0.01). Patients with influenza virus infection were older (p = 0.002), more frequently presented fever (p < 0.0001) and radiologic infiltrate (p < 0.001) than infants with RSV infection. Bronchiolitis was more frequent in the RSV group (p = 0.006).

CONCLUSIONS

Influenza infection is a major cause of respiratory tract disease in hospitalized infants. It is an etiologic cause of bronchiolitis, recurrent wheezing, and fever and radiologic consolidations are frequent. Clinical presentation is milder in children under 6 month of age. The characteristics of influenza infection differ substantially from those of RSV infection.

Laboratory-based influenza surveillance in New Caledonia, 1999-2003

We aimed to evaluate the annual incidence of influenza in New Caledonia and to identify the circulating viral types and subtypes in order to gather information for the local vaccination programme and regional influenza surveillance. A surveillance network was set up in 1999; it included sentinel practitioners in Noumea and the virology department of the Pasteur Institute. Influenza circulated in New Caledonia every year, regularly during the southern hemisphere winter and occasionally during March-May. Isolates were generally consistent with world surveillance, except in 1999, when a new A/H1N1 variant was identified. This study emphasises the need for regular influenza surveillance, even when performed on a limited scale. Importantly the optimal time for local vaccination was found to be in December or January each year.