Comparing Human Metapneumovirus and Respiratory Syncytial Virus: Viral Co-Detections, Genotypes and Risk Factors for Severe Disease

Increased Severity of Mycoplasma pneumoniae Infections in Spanish Children

BACKGROUND

Since the end of 2023, an elevated incidence and severity of Mycoplasma pneumoniae infections among children in Asia has been noted. Subsequently, this trend was observed in several European countries although limited data are currently available. We conducted a national study to delineate the ongoing M. pneumoniae outbreak in our country.

METHODS

A multicenter retrospective observational study was conducted across 32 hospitals in Spain, encompassing patients under 18 years old hospitalized for M. pneumoniae infection from January 2023 to March 2024. Infection was confirmed by positive polymerase chain reaction and/or by 2 serological tests.

RESULTS

A total of 623 children were included, with 79% of cases diagnosed in the final 3 months of the study period. Pneumonia was the most common diagnosis (87%). Respiratory symptoms were present in 97% of cases, with 62% requiring oxygen supplementation and 14% requiring admission to the pediatric intensive care unit (PICU). Risk factors for PICU admission included the presence of neurological symptoms, hypoxemia and a history of prematurity. Children admitted to the PICU exhibited significantly higher neutrophil counts upon admission.

CONCLUSIONS

We have observed a notable increase in hospital admissions, including PICU support by up to 14%, due to M. pneumoniae infection in our country since November 2023, indicative of a more severe clinical course associated with this pathogen.

Clinical comparison of HMPV and RSV infections in hospitalised Malaysian children: A propensity score matched study

INTRODUCTION

Human metapneumovirus (hMPV) and respiratory syncytial virus (RSV) are significant contributors to the burden of acute respiratory infections in children, but data on hMPV from Southeast Asia are limited despite its potential for serious disease. This study aimed to compare the clinical presentation, resource utilisation and outcomes between hMPV and RSV infections in hospitalised Malaysian children.

METHODS

This retrospective, observational study included children aged ≤12 years old hospitalised with hMPV or RSV, confirmed via direct fluorescent antibody (DFA) methods, between 1 July to 30 October 2022 at Hospital Tuanku Ja'afar Seremban, Malaysia. Demographic, clinical presentation, resource utilisation and outcome data were analysed. Propensity score matching was used to balance cohorts based on key demographic and clinical characteristics.

RESULTS

This study included 192 patients, comprising 112 with hMPV and 80 with RSV. hMPV patients were older (median age 20.5 vs. 9.4 months, p < 0.001) and had a higher incidence of comorbidities (24.1% vs. 7.5%, p = 0.003). Fever was more common in the hMPV group (97.3% vs. 73.8%, p < 0.001), but the other clinical manifestations were similar. Postmatching analysis showed higher corticosteroid use in the hMPV group (p = 0.01). No significant differences were observed in the use of other resources, PICU admissions, duration of hospitalisation or mortality rates between both groups.

CONCLUSION

hMPV and RSV infections in children share similar clinical manifestations and outcomes, with hMPV affecting older children and showing higher corticosteroid usage. These findings emphasise the need for equal clinical vigilance for both hMPV and RSV in paediatric respiratory infections.

Bronchial reactivity and asthma at school age after early-life metapneumovirus infection

Background

The association between early-life lower respiratory tract infection (LRTI) and asthma is well established. Knowledge about bronchial hyperresponsiveness (BHR) and asthma after metapneumovirus (MPV) LRTI is scarce. The aim of this study was to assess BHR and current asthma in school-aged children after hospital admission for early-life LRTI with MPV, and to compare with more well-known viruses, rhinovirus (RV) and respiratory syncytial virus (RSV), and with controls.

Methods

A cohort consisting of children admitted for LRTI and controls was followed-up at school age with a clinical research assessment and lung function tests, including a methacholine provocation test. Current asthma was defined based on objective variable airway obstruction and clinical symptoms. BHR and asthma were compared according to viral groups.

Results

135 children (median age 9.3 years) were included (16 MPV, 34 RV, 51 RSV, 13 mixed infections and 21 controls). Compared with controls there was increased BHR after MPV and RV LRTI (provocative dose causing a 20% fall in forced expiratory volume in 1 s and dose-response slope; p<0.05). Using Kaplan-Meier statistics, BHR was increased for MPV compared with both controls and RSV (p=0.02 and p=0.01). The proportion of children with current asthma at follow-up was higher in the LRTI children compared with the controls (46% versus 24%; p=0.06). Among children who had undergone MPV and RV infection, 50% fulfilled the asthma criteria compared with 43% in the RSV group (p=0.37).

Conclusion

We found increased BHR and a high prevalence of asthma in school-aged children after early-life MPV infection, and findings were similar to RV, and less to RSV, compared with controls.

Epidemiology and Clinical Features of Human Metapneumovirus and Respiratory Syncytial Viral Infections in Children

BACKGROUND

Human metapneumovirus (HMPV) and respiratory syncytial virus (RSV) are 2 common causes of acute respiratory tract infections in infants and young children. The objective of this study is to compare the demographics and outcomes of children hospitalized with HMPV and RSV infections in the United States.

METHODS

We performed a retrospective cohort analysis of children 1 month to less than 3 years old discharged during 2016 with HMPV or RSV infection using the Kids' Inpatient Database. Children with HMPV and RSV coinfection were excluded. Data were weighted for national estimates.

RESULTS

There were 6585 children with HMPV infection and 70,824 with RSV infection discharged during the study period. The mean age of children with HMPV infection was higher than that of children with RSV infection (0.73 ± 0.8 vs. 0.42 ± 0.7 years; P < 0.05). The mortality rate was significantly higher in children with the presence of any complex chronic conditions compared to those without, in both HMPV [odds ratio (OR): 32.42; CI: 9.931-105.857; P < 0.05] as well as RSV (OR: 35.81; CI: 21.12-57.97; P < 0.05) groups. The adjusted median length of stay was longer (4.64 days; CI: 4.52-4.76 days vs. 3.33 days; CI: 3.31-3.35 days; P < 0.001) and total charges were higher ($44,358; CI: $42,145-$46,570 vs. $22,839; CI: $22,512-$23,166; P < 0.001), with HMPV infection. The mortality rate was similar in HMPV infection compared to RSV infection on multivariable analysis (OR: 1.48; P > 0.05).

CONCLUSION

In hospitalized children in the United States, HMPV infection is less common than RSV infection. Complex chronic conditions are more prevalent in children hospitalized with HMPV infection. Hospitalization with HMPV is associated with longer length of stay and higher hospital charges. The adjusted mortality is similar with both infections.

Selenadiazole Inhibited Adenovirus-Induced Apoptosis through the Oxidative-Damage-Mediated Bcl-2/Stat 3/NF-κB Signaling Pathway

Human adenovirus type 7 (HAdV7) infection causes severe pneumonia, yet there are still no breakthroughs in treatment options for adenovirus, and the road to antiviral drug development faces major challenges. We attempted to find new drugs and we stumbled upon one: selenadiazole. Selenadiazole has been shown to have significant anti-tumor effects due to its unique chemical structure and drug activity. However, its effectiveness against viruses has not been evaluated yet. In our study, selenadiazole also showed superior antiviral activity. In vitro experiments, selenadiazole was able to inhibit adenovirus-mediated mitochondrial-oxidative-damage-related apoptosis, and in in vivo experiments, selenadiazole was able to inhibit apoptosis by modulating the apoptotic signaling pathway Bcl-2/Stat3/NF-κB, etc., and was able to largely attenuate adenovirus-infection-induced pneumonia and lung injury in mice. This study aims to describe a new antiviral treatment option from the perspective of anti-adenovirus-mediated oxidative stress and its associated apoptosis and to provide theoretical guidance for the treatment of clinical adenovirus infection to a certain extent.

A decade of human metapneumovirus in hospitalized children with acute respiratory infection: molecular epidemiology in central Vietnam, 2007-2017

Human metapneumovirus (hMPV) can cause severe acute respiratory infection (ARI). We aimed to clarify the clinical and molecular epidemiological features of hMPV. We conducted an ARI surveillance targeting hospitalized children aged 1 month to 14 years in Nha Trang, Vietnam. Nasopharyngeal swabs were tested for respiratory viruses with PCR. We described the clinical characteristics of hMPV patients in comparison with those with respiratory syncytial virus (RSV) and those with neither RSV nor hMPV, and among different hMPV genotypes. Among 8822 patients, 278 (3.2%) were hMPV positive, with a median age of 21.0 months (interquartile range: 12.7-32.5). Among single virus-positive patients, hMPV cases were older than patients with RSV (p < 0.001) and without RSV (p = 0.003). The proportions of clinical pneumonia and wheezing in hMPV patients resembled those in RSV patients but were higher than in non-RSV non-hMPV patients. Seventy percent (n = 195) were genotyped (A2b: n = 40, 20.5%; A2c: n = 99, 50.8%; B1: n = 37, 19%; and B2: n = 19, 9.7%). The wheezing frequency was higher in A2b patients (76.7%) than in those with other genotypes (p = 0.033). In conclusion, we found a moderate variation in clinical features among hMPV patients with various genotypes. No seasonality was observed, and the multiple genotype co-circulation was evident.

Risk Factors Associated with Severe RSV Infection in Infants: What Is the Role of Viral Co-Infections?

The respiratory syncytial virus (RSV) represents the leading cause of viral lower respiratory tract infections (LRTI) in children worldwide and is associated with significant morbidity and mortality rates. The clinical picture of an RSV infection differs substantially between patients, and the role of viral co-infections is poorly investigated. During two consecutive winter seasons from October 2018 until February 2020, we prospectively included children up to 2 years old presenting with an acute LRTI, both ambulatory and hospitalized. We collected clinical data and tested nasopharyngeal secretions for a panel of 16 different respiratory viruses with multiplex RT-qPCR. Disease severity was assessed with traditional clinical parameters and scoring systems. A total of 120 patients were included, of which 91.7% were RSV positive; 42.5% of RSV-positive patients had a co-infection with at least one other respiratory virus. We found that patients suffering from a single RSV infection had higher pediatric intensive care unit (PICU) admission rates (OR = 5.9, 95% CI = 1.53 to 22.74), longer duration of hospitalization (IRR = 1.25, 95% CI = 1.03 to 1.52), and a higher Bronchiolitis Risk of Admission Score (BRAS) (IRR = 1.31, 95% CI = 1.02 to 1.70) compared to patients with RSV co-infections. No significant difference was found in saturation on admission, O2 need, or ReSViNET-score. In our cohort, patients with a single RSV infection had increased disease severity compared to patients with RSV co-infections. This suggests that the presence of viral co-infections might influence the course of RSV bronchiolitis, but heterogeneity and small sample size in our study prevents us from drawing strong conclusions. IMPORTANCE RSV is worldwide the leading cause of serious airway infections. Up to 90% of children will be infected by the age of 2. RSV symptoms are mostly mild and typically mimic a common cold in older children and adolescents, but younger children can develop severe lower respiratory tract disease, and currently it is unclear why certain children develop severe disease while others do not. In this study, we found that children with a single RSV infection had a higher disease severity compared to patients with viral co-infections, suggesting that the presence of a viral co-infection could influence the course of an RSV bronchiolitis. As preventive and therapeutic options for RSV-associated disease are currently limited, this finding could potentially guide physicians to decide which patients might benefit from current or future treatment options early in the course of disease, and therefore, warrants further investigation.

Profile analysis of emerging respiratory virus in children

Acute respiratory infections (ARIs) are caused by a variety of microorganisms. Of all ARIs, 80% are caused by viruses such as human respiratory syncytial virus, metapneumovirus, influenza, parainfluenza, rhinovirus, and, more recently, Sars-CoV-2, which has been responsible for the COVID-19 pandemic. The objective of our study was to evaluate clinical data from a viral panel performed in children hospitalized with SARS or COVID-19 in the infirmary or ICU of 5 pediatric hospitals in the city of Goiânia, Goiás, Brazil. Demographic, clinical, and laboratory data were collected for analysis, and data on the outcomes underwent statistical treatment. A total of 128 patients were selected for the study, 54% of whom were male and 46% female. The viral panel included rhinovirus, COVID-19, metapneumovirus, adenovirus, and parainfluenza. Descriptive analyses of age profile showed differences in the involvement of particular viruses. The percentage of patients who required hospitalization in the ICU, infirmary, as well as individuals who were discharged after therapy or who died, were described. Our work shows that epidemiological surveillance measures are indispensable, especially if used in the continued analysis of viral panels in all pediatric patients with SARS.

The Common Cold and Influenza in Children: To Treat or Not to Treat?

The common cold, which is mostly caused by respiratory viruses and clinically represented by the symptoms of acute respiratory viral infections (ARVI) with mainly upper respiratory tract involvement, is an important problem in pediatric practice. Due to the high prevalence, socio-economic burden, and lack of effective prevention measures (except for influenza and, partially, RSV infection), ARVI require strong medical attention. The purpose of this descriptive literature review was to analyze the current practical approaches to the treatment of ARVI to facilitate the choice of therapy in routine practice. This descriptive overview includes information on the causative agents of ARVI. Special attention is paid to the role of interferon gamma as a cytokine with antiviral and immunomodulatory effects on the pathogenesis of ARVI. Modern approaches to the treatment of ARVI, including antiviral, pathogenesis-directed and symptomatic therapy are presented. The emphasis is on the use of antibody-based drugs in the immunoprophylaxis and immunotherapy of ARVI. The data presented in this review allow us to conclude that a modern, balanced and evidence-based approach to the choice of ARVI treatment in children should be used in clinical practice. The published results of clinical trials and systematic reviews with meta-analyses of ARVI in children allow us to conclude that it is possible and expedient to use broad-spectrum antiviral drugs in complex therapy. This approach can provide an adequate response of the child’s immune system to the virus without limiting the clinical possibilities of using only symptomatic therapy.

The Contribution of Viruses and Bacteria to Childhood Community-acquired Pneumonia: 11-Year Observational Study From Norway

BACKGROUND

Viruses are associated with pediatric community-acquired pneumonia (CAP) but are also common in the upper airways of healthy children. We have determined the contribution of respiratory viruses and bacteria by comparing children with CAP and hospital controls.

METHODS

Children less than 16 years old with radiologically confirmed CAP (n = 715) were enrolled over an 11-year period. Children admitted for elective surgery during the same period served as controls (n = 673). Nasopharyngeal aspirates were tested for 20 respiratory pathogens by semiquantitative polymerase chain reaction tests and cultivated for bacteria and viruses. We used logistic regression to calculate adjusted odds ratios [aOR; 95% confidence intervals (CIs)], and estimated population-attributable fractions (95% CI).

RESULTS

At least 1 virus was detected in 85% of cases and 76% of controls, and greater than or equal to 1 bacterium was detected in 70% of cases and controls. The presence of respiratory syncytial virus (RSV) (aOR, 16.6; 95% CI: 9.81-28.2), human metapneumovirus (HMPV) (13.0; 6.17-27.5) and Mycoplasma pneumonia e (27.7; 8.37-91.6) were most strongly associated with CAP. For RSV and HMPV, there were significant trends between lower cycle-threshold values indicating higher viral genomic loads, and higher aORs for CAP. The population-attributable fraction estimates of RSV, HMPV, human parainfluenza virus, influenza virus and M. pneumoniae were 33.3% (32.2-34.5), 11.2% (10.5-11.9), 3.7% (1.0-6.3), 2.3% (1.0-3.6) and 4.2% (4.1-4.4), respectively.

CONCLUSIONS

RSV, HMPV and M. pneumoniae were most strongly related to pediatric CAP and accounted for half of all cases. There were positive trends between increasing viral genomic loads of RSV and HMPV, and higher odds for CAP.

Human Metapneumovirus-Associated Hospitalization in HIV-1 Exposed Uninfected and HIV-1 Uninfected Children Less Than 5 Years in South Africa

Using hospital surveillance data, we estimated Human metapneumovirus (hMPV) hospitalization incidence by age and HIV-exposure status. hMPV-associated hospitalization incidence was highest in <1-year children. Incidence rate ratios of HIV-exposed over unexposed children were 1.5 (95%CI 0.9-2.4) for <6-month children, 1.4 (95%CI 0.7-2.4) for 6- to 11-month children and 0.9 (95%CI 0.4-1.9) for 12- to 59-month children.

Profiles and predictive value of cytokines in children with human metapneumovirus pneumonia

BACKGROUND

Human metapneumovirus (HMPV) is an important cause of respiratory tract infections in young children. Early innate immune response to HMPV is focused on induction of antiviral interferons (IFNs) and other pro-inflammatory cytokines that are critical for the formation of adaptive immune responses. To evaluate the predictive value of Th1/Th2 cytokines which include IL-2, IL-4, IL-6, IL-10, INF-γ and TNF-α in pneumonia caused by HMPV.

METHODS

A retrospective study was performed among 59 pneumonia pediatric patients with HMPV infection and 33 healthy children as the control cohort, which was detected by the immunofluorescence assay, and the Th1/Th2 cytokines were measured by flow cytometry. 131 children infected with Influenza virus A (IVA) and 41 children infected with influenza virus B (IVB) were detected by RT-PCR assay in throat swabs.

RESULTS

When compared with the healthy children, children who were infected with HMPV pneumonia had a significantly lower level of IL-2 (p < 0.001) and higher levels of IL-4 (p < 0.001), IL-6 (p = 0.001), IL-10 (p < 0.001), and IFN-γ (p < 0.001). Compared with patients diagnosed with IVA or IVB infection, HMPV-positive patients had significantly higher levels of IL-4 (p < 0.001 and < 0.001), IFN-γ (p < 0.001 and < 0.001), and TNF-α (p < 0.001 and 0.016). Moreover, compared with IVA patients, HMPV-positive patients had a significantly lower level of IL-6 (p = 0.033). Finally, when comparing cytokine levels among the patients with HMPV pneumonia, IL-6 and TNF-α levels were found to be significantly higher in the severe group than the mild group (p = 0.027 and 0.049). The IL-6 and TNF-α were used to differentiate between mild symptoms and severe symptoms in children diagnosed with HMPV pneumonia with an AUC of 0.678 (95% CI 0.526-0.829) and 0.658 (95% CI 0.506-0.809), respectively.

CONCLUSION

Our study indicated that difference in cytokine trends depending on the virus species. The levels of IL-4, TNF-α and IFN-γ were significantly distinguished in children infected with HMPV versus IVA and IVB. IL-6 and TNF-α may be helpful in assessing the severity and prognosis of HMPV infection.

Epidemiology and genetic characterization of human metapneumovirus in pediatric patients from Hangzhou China

Human metapneumovirus (HMPV), which is distributed worldwide, is a significant viral respiratory pathogen responsible for causing acute respiratory tract infections (ARTIs) in children. The aim of the present study was to investigate the epidemiological and genetic characteristics of HMPV in pediatric patients in Hangzhou China following the peak of onset of coronavirus disease 2019 (COVID-19). A total of 1442 throat swabs were collected from the pediatric patients with a diagnosis of ARTI from November 2020 to March 2021. The following viruses were detected by real-time polymerase chain reaction analysis: HMPV, RSV, adenovirus, hPIV1-3, influenza A, and influenza B. A two-step method was used to amplify the F genes of the HMPV-positive samples. Following sequencing, phylogenetic analyses were conducted using the MEGA version 7 software package. Among the 1442 samples, 103 (7.14%) were positive for HMPV. No significant differences were observed in the gender distribution. The highest incidence of HMPV occurred in children older than 6 years and the lowest was noted in children younger than 6 months. Lower respiratory tract infections were diagnosed at a higher rate than upper respiratory tract infections in HMPV-infected children. Only 10 HMPV-infected children (5.41%) were inpatients compared with 93 outpatients (7.39%). Co-infection was observed in 31 HMPV-positive samples including 24 samples of double infection and seven samples of triple infection. A total of 61F gene fragments of HMPV, which were approximately 727 bp in length were successfully sequenced. All the HMPVs belonged to the genotype B and were clustered into subgenotypes B1 (1.6%, 1/61) and B2 (98.4%, 60/61). A total of four specific amino acid substitutions were noted as follows: aa280, aa296, aa392, and aa396. These substitutions were present between sequences derived from the subgenotypes B1 and B2 in the fusion open reading frame from position 244 to 429. In conclusion, the present study provided significant information regarding the epidemiological and genetic characteristics of HMPV in children living in Hangzhou. Following the first peak of the COVID-19 pandemic, HMPV was considered an important viral respiratory pathogen present in children with ARTI.

Detection of subgenomic mRNA from endemic human coronavirus OC43 and NL63 compared to viral genomic loads, single virus detection and clinical manifestations in children with respiratory tract infections

Background

The importance of endemic human coronavirus (HCoV) in children has been insufficiently elucidated upon. Our aims were to develop subgenomic (sg) mRNA tests for HCoV species OC43 and NL63, and to evaluate the relationships to HCoV genomic loads, single HCoV detections and clinical manifestations.

Methods

We have used an 11-yearlong cohort study of children admitted with respiratory tract infection (RTI) and hospital controls. Nasopharyngeal aspirates were analyzed for HCoV subtypes OC43 and NL63 with in-house diagnostic PCR. Positive samples were tested with newly developed real-time PCRs targeting sg mRNA coding for the nucleocapsid protein.

Results

OC43 sg mRNA was detected in 86% (105/122) of available OC43-positive samples in the RTI group, and in 63% (12/19) of control samples. NL63 sg mRNA was detected in 72% (71/98) and 71% (12/17) of available NL63-positive patient and control samples, respectively. In RTI samples, sg mRNA detection was strongly associated with a Ct value <32 in both diagnostic PCR tests (OC43: OR = 54, 95% CI [6.8–428]; NL63: OR = 42, 95% CI [9.0–198]) and single NL63 detections (OR = 6.9, 95% CI [1.5–32]). Comparing RTI and controls, only OC43 was associated with RTI when adjusted for age (aOR = 3.2, 95% CI [1.1–9.4]).

Conclusion

We found strong associations between OC43 and NL63 sg mRNA and high viral genomic loads. sg mRNA for OC43 was associated with RTI. The association between sg mRNA and clinical manifestations needs further evaluation.

Human Metapneumovirus Infection in a Children's Hospital - It Should Get More Attention

BACKGROUND

Respiratory syncytial virus (RSV) and influenza infections are a major cause of hospitalization and intensive care unit (ICU) admission to children's hospitals and are closely tracked. We compared data over 6 seasons of human metapneumovirus (hMPV), RSV and influenza infections.

METHODS

During the 2014-2019 winter viral seasons, hMPV, RSV and influenza infections were tracked. For hMPV admissions, rates of hospitalizations, ICU admissions, hospital-acquired infections (HAIs) and mortalities were assessed and compared with RSV and influenza admissions. Retrospective data was used to study patients infected with hMPV.

RESULTS

During the winter seasons of 2014-2019, the rates of hospitalization due to hMPV were significantly higher than both RSV and influenza. ICU admissions, deaths and HAIs for hMPV were similar to RSV and influenza.Of the 471 total cases with hMPV, 58 (12.3%) had chronic lung disease (CLD) and 23 (4.9%) were tracheostomy dependent. Among 104 hMPV ICU admissions from 2013 to 2019, 86 (82%) had an underlying medical diagnosis, 30 (29%) had CLD, 21 (20%) had tracheostomies and 33 (32%) required mechanical ventilation. The average age of hMPV infected children in our ICU is 3 years and 10 months.

CONCLUSIONS

Our large descriptive study of hMPV infected children over 6 seasons showed higher rates of hospitalization compared with RSV and influenza, similar ICU and HAI rates, and deaths. ICU admitted children often had associated co-morbidities, including CLD. Further studies for focused disease surveillance and potential vaccine development for high-risk children are needed.

Molecular investigation of human metapneumovirus in children with acute respiratory infections in Chennai, South India, from 2016-2018

Human metapneumovirus (hMPV) has emerged as a frequent cause of acute respiratory infections (ARI) among young children. The prevalence and genetic diversity of hMPV circulating in Chennai, Southern India, has not been studied yet. Hence, this study was aimed to investigate the prevalence, co-infection with other respiratory viruses like HRSV A and B, influenza A and B, hRV and HPIV 1-4 viruses, socio-demographic associations, and genotypes of hMPV among children in Chennai. A total of 350 nasal swab specimens were collected from children with ARI during April 2016 to August 2018 and tested for hMPV by real time PCR method. In this study, hMPV was detected in 4% (14/350) of the samples. One hMPV positive sample was found to be co-infected with influenza B virus. The mean and median ages of the children with hMPV infection were 61.5 months (5.1 years) and 83 months (6.9 years), respectively. Phylogenetic analysis of the partial F gene revealed the presence of A2c subcluster among the study strains as well as with B1 and B2 lineages. The prevalence data obtained in this study is important in evaluating the role of hMPV in childhood ARI and emphasizes the importance of routine viral diagnosis in hospitals. To the best of our knowledge, this is the first study to report the prevalence, seasonality, and genetic diversity of hMPV in Chennai as well as the first study to report A2c subcluster of hMPV among children in India.

The Prevalence and Genetic Characterization of Human Metapneumovirus in Bulgaria, 2016-2019

INTRODUCTION

We investigated the prevalence of human metapneumovirus (hMPV) among patients with acute respiratory infections in Bulgaria, and performed genetic characterization of the F gene of these strains.

METHODS

Nasopharyngeal swabs collected from patients of a range of ages were tested by using real-time PCR for 12 respiratory viruses. The F gene was sequenced, and phylogenetic and amino acid analyses of the F gene/protein were performed.

RESULTS

A total of 1,842 patients were examined during a 3-year period; 1,229 patients (66.7%) were positive for at least one respiratory virus. hMPV was identified in 83 (4.5%) patient samples. Eleven (13%) of hMPV-positive patients were coinfected with another respiratory virus. The hMPV incidence rate in the 2016/2017, 2017/2018, and 2018/2019 winter seasons was 5.4, 5.4, and 3.1%, respectively. hMPV was mainly detected in specimens collected between January and May (89.2% of cases). The incidence of hMPV infection was highest (5.1%) among the youngest age-group (0-4 years), where hMPV was a causative agent in 8.1 and 4.8% of bronchiolitis and pneumonia cases, respectively. Among the patients aged ≥5 years, hMPV was detected in 2.2 and 3.2% of cases of pneumonia and central nervous system infections, respectively. Phylogenetic analysis of the F gene showed that the sequenced hMPV strains belonged to the A2b, B1, and B2 genotypes. Numerous amino acid substitutions were identified compared with the NL00/1 prototype strain.

CONCLUSION

This study revealed the significant role of hMPV as a causative agent of serious respiratory illnesses in early childhood, and also demonstrated year-to-year changes in hMPV prevalence and genetic diversity in circulating strains.

Bacterial and Viral Coinfections with the Human Respiratory Syncytial Virus

The human respiratory syncytial virus (hRSV) is one of the leading causes of acute lower respiratory tract infections in children under five years old. Notably, hRSV infections can give way to pneumonia and predispose to other respiratory complications later in life, such as asthma. Even though the social and economic burden associated with hRSV infections is tremendous, there are no approved vaccines to date to prevent the disease caused by this pathogen. Recently, coinfections and superinfections have turned into an active field of study, and interactions between many viral and bacterial pathogens have been studied. hRSV is not an exception since polymicrobial infections involving this virus are common, especially when illness has evolved into pneumonia. Here, we review the epidemiology and recent findings regarding the main polymicrobial infections involving hRSV and several prevalent bacterial and viral respiratory pathogens, such as Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Klebsiella pneumoniae, human rhinoviruses, influenza A virus, human metapneumovirus, and human parainfluenza viruses. As reports of most polymicrobial infections involving hRSV lack a molecular basis explaining the interaction between hRSV and these pathogens, we believe this review article can serve as a starting point to interesting and very much needed research in this area.

Comparative analysis of spatial-temporal patterns of human metapneumovirus and respiratory syncytial virus in Africa using genetic data, 2011-2014

BACKGROUND

Human metapneumovirus (HMPV) and respiratory syncytial virus (RSV) are leading causes of viral severe acute respiratory illnesses in childhood. Both the two viruses belong to the Pneumoviridae family and show overlapping clinical, epidemiological and transmission features. However, it is unknown whether these two viruses have similar geographic spread patterns which may inform designing and evaluating their epidemic control measures.

METHODS

We conducted comparative phylogenetic and phylogeographic analyses to explore the spatial-temporal patterns of HMPV and RSV across Africa using 232 HMPV and 842 RSV attachment (G) glycoprotein gene sequences obtained from 5 countries (The Gambia, Zambia, Mali, South Africa, and Kenya) between August 2011 and January 2014.

RESULTS

Phylogeographic analyses found frequently similar patterns of spread of RSV and HMPV. Viral sequences commonly clustered by region, i.e., West Africa (Mali, Gambia), East Africa (Kenya) and Southern Africa (Zambia, South Africa), and similar genotype dominance patterns were observed between neighbouring countries. Both HMPV and RSV country epidemics were characterized by co-circulation of multiple genotypes. Sequences from different African sub-regions (East, West and Southern Africa) fell into separate clusters interspersed with sequences from other countries globally.

CONCLUSION

The spatial clustering patterns of viral sequences and genotype dominance patterns observed in our analysis suggests strong regional links and predominant local transmission. The geographical clustering further suggests independent introduction of HMPV and RSV variants in Africa from the global pool, and local regional diversification.

Clinical impact of human metapneumovirus infections before and during the COVID-19 pandemic

BACKGROUND

The first outbreak of coronavirus disease 2019 (COVID-19) occurred in March 2020 in Europe, which is normally the peak incidence period of human metapneumovirus (HMPV) infections, implying cocirculation and potentially causing competition between them.

METHODS

We investigated differences in clinical characteristics and outcomes of HMPV infections in hospitalized patients before (January 2016-28 February, 2020) and HMPV and COVID-19 during part of the COVID-19 pandemic (28 February, 2020-1 April, 2020).

RESULTS

A total of 239 HMPV patients and 303 COVID-19 patients were included. Incidence of HMPV peaked in March. Despite a 324% increase in HMPV testing during the COVID-19 outbreak, incidence of HMPV remained stable. Clinical characteristics showed 25 (11%) ICU admissions and 14 (6%) deaths. History of myocardial infarction, higher age and lower BMI were independently associated with increased 30-day mortality. Clinical characteristics of HMPV-infected patients did not differ between the non-COVID-19 period and the examined COVID-19 period except for length of hospital stay (7 vs. 5 days). HMPV infection and COVID-19 shared many clinical features but HMPV was associated with female gender, elderly patients and chronic conditions (COPD and chronic heart failure). Clinical outcomes did not differ between the viruses during the COVID-19 period.

CONCLUSIONS

The clinical impact of HMPV infection did not change during the COVID-19 outbreak in terms of incidence and/or disease severity; hence, HMPV and SARS-CoV-2 are probably co-circulating independently. Despite the current clinical focus on the COVID-19 pandemic, clinicians should keep in mind that HMPV-infection may mimic COVID-19 and is also associated with serious adverse outcomes.

Contribution of NKT cells to the immune response and pathogenesis triggered by respiratory viruses

Human respiratory syncytial virus (hRSV) and human metapneumovirus (hMPV) cause acute respiratory tract infections in children worldwide. Natural killer T (NKT) cells are unconventional T lymphocytes, and their TCRs recognize glycolipids bound to the MHC-I-like molecule, CD1d. These cells modulate the inflammatory response in viral infections. Here, we evaluated the contribution of NKT cells in both hRSV and hMPV infections. A significant decrease in the number of neutrophils, eosinophils, and CD103⁺DCs infiltrating to the lungs, as well as an increased production of IFN-γ, were observed upon hRSV-infection in CD1d-deficient BALB/c mice, as compared to wild-type control mice. However, this effect was not observed in the CD1d-deficient BALB/c group, upon infection with hMPV. Importantly, reduced expression of CD1d in CD11b⁺ DCs and epithelial cells was found in hRSV -but not hMPV-infected mice. Besides, a reduction in the expression of CD1d in alveolar macrophages of lungs from hRSV- and hMPV-infected mice was found. Such reduction of CD1d expression interfered with NKT cells activation, and consequently IL-2 secretion, as characterized by in vitro experiments for both hRSV and hMPV infections. Furthermore, increased numbers of NKT cells recruited to the lungs in response to hRSV- but not hMPV-infection was detected, resulting in a reduction in the expression of IFN-γ and IL-2 by these cells. In conclusion, both hRSV and hMPV might be differently impairing NKT cells function and contributing to the immune response triggered by these viruses.

RSV and HMPV Infections in 3D Tissue Cultures: Mechanisms Involved in Virus-Host and Virus-Virus Interactions

Respiratory viral infections constitute a global public health concern. Among prevalent respiratory viruses, two pneumoviruses can be life-threatening in high-risk populations. In young children, they constitute the first cause of hospitalization due to severe lower respiratory tract diseases. A better understanding of their pathogenesis is still needed as there are no approved efficient anti-viral nor vaccine against pneumoviruses. We studied Respiratory Syncytial virus (RSV) and human Metapneumovirus (HMPV) in single and dual infections in three-dimensional cultures, a highly relevant model to study viral respiratory infections of the airway epithelium. Our investigation showed that HMPV is less pathogenic than RSV in this model. Compared to RSV, HMPV replicated less efficiently, induced a lower immune response, did not block cilia beating, and was more sensitive to IFNs. In dual infections, RSV-infected epithelia were less permissive to HMPV. By neutralizing IFNs in co-infection assays, we partially prevented HMPV inhibition by RSV and significantly increased the number of co-infected cells in the tissue. This suggests that interference in dual infection would be at least partly mediated by the host immune response. In summary, this work provides new insight regarding virus-host and virus-virus interactions of pneumoviruses in the airway epithelium. This could be helpful for the proper handling of at-risk patients.

INFECTIONS IN PREGNANCY WITH COVID-19 AND OTHER RESPIRATORY RNA VIRUS DISEASES ARE RARELY, IF EVER, TRANSMITTED TO THE FETUS: EXPERIENCES WITH CORONAVIRUSES, HPIV, hMPV RSV, AND INFLUENZA

SARS-CoV-2, the agent of COVID-19, is similar to two other coronaviruses, SARS-CoV and MERS-CoV, in causing life-threatening maternal respiratory infections and systemic complications. Because of global concern for potential intrauterine transmission of SARS-CoV-2 from pregnant women to their infants, this report analyzes the effects on pregnancy of infections caused by SARS-CoV-2 and other respiratory RNA viruses, and examines the frequency of maternal-fetal transmission with SARS-CoV-2, severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), influenza, respiratory syncytial virus (RSV), parainfluenza (HPIV) and metapneumovirus (hMPV). There have been no confirmed cases of intrauterine transmission reported with COVID-19 or any other coronavirus infections. Influenza virus, despite causing approximately one billion annual infections globally, has only a few cases of confirmed or suspected intrauterine fetal infections reported. RSV is in an unusual cause of illness among pregnant women, and with the exception of one premature infant with congenital pneumonia, no other cases of maternal-fetal infection are described. Parainfluenza virus and human metapneumovirus can produce symptomatic maternal infections but do not cause intrauterine fetal infection. In summary, it appears that the absence thus far of maternal-fetal transmission of the SARS-CoV-2 virus during the COVID-19 pandemic is similar to other coronaviruses, and is also consistent with the extreme rarity of suggested or confirmed cases of intrauterine transmission of other respiratory RNA viruses. This observation has important consequences for pregnant women as it appears that if intrauterine transmission of SARSCoV-2 does eventually occur, it will be a rare event. Potential mechanisms of fetal protection from maternal viral infections are also discussed.

Non-Coding RNAs and Their Role in Respiratory Syncytial Virus (RSV) and Human Metapneumovirus (hMPV) Infections

Recent high-throughput sequencing revealed that only 2% of the transcribed human genome codes for proteins, while the majority of transcriptional products are non-coding RNAs (ncRNAs). Herein, we review the current knowledge regarding ncRNAs, both host- and virus-derived, and their role in respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) infections. RSV is known as the most common cause of lower respiratory tract infection (LRTI) in children, while hMPV is also a significant contributor to LRTI in the pediatrics population. Although RSV and hMPV are close members, belonging to the Pneumoviridae family, they induce distinct changes in the ncRNA profile. Several types of host ncRNAs, including long ncRNA (lncRNA), microRNAs (miRNAs), and transfer RNA (tRNA)-derived RNA fragments (tRFs), are involved as playing roles in RSV and/or hMPV infection. Given the importance of ncRNAs in regulating the expression and functions of genes and proteins, comprehensively understanding the roles of ncRNAs in RSV/hMPV infection could shed light upon the disease mechanisms of RSV and hMPV, potentially providing insights into the development of prevention strategies and antiviral therapy. The presence of viral-derived RNAs and the potential of using ncRNAs as diagnostic biomarkers are also discussed in this review.

Engineering of Live Chimeric Vaccines against Human Metapneumovirus

Human metapneumovirus (HMPV) is an important human pathogen that, along with respiratory syncytial virus (RSV), is a major cause of respiratory tract infections in young infants. Development of an effective vaccine against Pneumoviruses has proven to be particularly difficult; despite over 50 years of research in this field, no vaccine against HMPV or RSV is currently available. Recombinant chimeric viruses expressing antigens of other viruses can be generated by reverse genetics and used for simultaneous immunization against more than one pathogen. This approach can result in the development of promising vaccine candidates against HMPV, and several studies have indeed validated viral vectors expressing HMPV antigens. In this review, we summarize current efforts in generating recombinant chimeric vaccines against HMPV, and we discuss their potential optimization based on the correspondence with RSV studies.

Human Metapneumovirus: A Largely Unrecognized Threat to Human Health

Human metapneumovirus (HMPV) infects most children by five years of age. The virus can cause both upper and lower respiratory tract disease and can be life threatening. High-risk populations include young children who are exposed to virus for the first time and the elderly. Currently, there is no standard treatment nor licensed vaccine for HMPV, although several attractive vaccine candidates have been developed for pre-clinical studies. A raised awareness of the impact of HMPV on public health is needed to drive research, complete vaccine development, and thereby prevent significant virus-associated morbidities and mortalities worldwide.

Role for Maternal Asthma in Severe Human Metapneumovirus Lung Disease Susceptibility in Children

Background

Severity of human metapneumovirus (hMPV) lower respiratory illness (LRTI) is considered similar to that observed for respiratory syncytial virus (RSV). However, differences in severity between these pathogens have been noted, suggesting the degree of illness may vary in different populations. Moreover, a potential association between hMPV and asthma also suggests that hMPV may preferentially affect asthmatic subjects.

Methods

In a population-based surveillance study in children aged <2 years admitted for severe LRTI in Argentina, nasopharyngeal aspirates were tested by RT-PCR for hMPV, RSV, influenza A, and human rhinovirus.

Results

Of 3947 children, 383 (10%) were infected with hMPV. The hospitalization rate for hMPV LRTI was 2.26 per 1000 children (95% confidence interval [CI], 2.04–2.49). Thirty-nine (10.2%) patients infected with hMPV experienced life-threatening disease (LTD; 0.23 per 1000 children; 95% CI, .16–.31/1000), and 2 died (mortality rate 0.024 per 1000; 95% CI, .003–.086). In hMPV-infected children birth to an asthmatic mother was an increased risk for LTD (odds ratio, 4.72; 95% CI, 1.39–16.01). We observed a specific interaction between maternal asthma and hMPV infection affecting risk for LTD.

Conclusions

Maternal asthma increases the risk for LTD in children <2 years old hospitalized for severe hMPV LRTI.

Epidemiological and genetic characteristics of human metapneumovirus in pediatric patients across six consecutive seasons in Beijing, China

OBJECTIVES

To investigate the genetic characteristics of human metapneumovirus (hMPV) circulating among children with acute respiratory tract infections (ARTIs) in Beijing, China.

METHODS

Clinical samples were obtained from outpatients and hospitalized children with ARTIs between August 2010 and July 2016. Reverse transcription polymerase chain reaction assays were used to screen and identify hMPV, while partial glycoprotein gene sequences were used for phylogenetic analysis.

RESULTS

Among the 10 918 samples, 292 (2.7%) were positive for hMPV. Overall, the virus was more prevalent among inpatients (4.3%) than outpatients (1.2%). A biennial alternating pattern of hMPV infection was observed, with infection rates fluctuating between 1.6% and 4.0%. Most cases were detected between December and April, showing clear-cut seasonality. Sub-genotypes A2b, B1, and B2 co-circulated in winter and spring in an alternating pattern, while only one A1-positive case was observed in 2012. The seasonal peak of hMPV was slightly delayed or overlapped with that of respiratory syncytial virus and influenza virus. hMPV activity increased in the 2010-2011 and 2014-2015 seasons, when influenza activity was apparently decreased compared with other epidemic seasons.

CONCLUSIONS

This study provides information on the epidemiological and genetic characteristics of hMPV in children in Beijing, and reinforces the significance of hMPV in children with ARTIs, especially lower respiratory tract infections.

Comparison of Rates of Hospitalization Between Single and Dual Virus Detection in a Mexican Cohort of Children and Adults With Influenza-Like Illness

BACKGROUND

Molecular detection methods allow for the simultaneous detection of several infectious agents. This study assesses whether co-infection with 2 viruses as compared with 1 is associated with increased hospitalization in those with acute respiratory infections.

METHODS

We prospectively enrolled a cohort of pediatric and adult participants with influenza-like illness during 2010-2014 in Mexico. Clinical information and respiratory samples were collected at enrollment. Respiratory viruses were detected with multiplex polymerase chain reaction (PCR) and influenza-specific reverse transcription PCR assays. Participants were followed for 14 and 28 days after inclusion. Severity of disease, as measured by hospitalization with acute respiratory infections, was compared between single and dual viral infections.

RESULTS

Among 5662 participants in the study, either 1 (n = 3285) or 2 (n = 641) viruses were detected in 3926 participants. Rhinovirus (n = 1433), influenza (n = 888), and coronaviruses (n = 703) were the most frequently detected viruses (either alone or in co-infection). Bocavirus, respiratory syncytial virus (RSV), metapneumovirus, and rhinovirus cases were hospitalized more often than other viruses. Bocavirus+rhinovirus cases were hospitalized more often than those with rhinovirus alone (but not bocavirus alone). RSV cases were more likely to be hospitalized than cases with co-infections of RSV and parainfluenza virus or coronavirus. Metapneumovirus cases were hospitalized more often than those co-infected with metapneumovirus+coronavirus.

CONCLUSIONS

In this study, detection of 2 viruses did not significantly increase hospitalizations compared with single virus infections. Larger studies will allow for distinguishing between sequential and simultaneous infection and for a better understanding of the role of each virus during the evolution of acute respiratory episodes.

Human metapneumovirus prevalence and patterns of subgroup persistence identified through surveillance of pediatric pneumonia hospital admissions in coastal Kenya, 2007-2016

BACKGROUND

Human metapneumovirus (HMPV) is an important respiratory pathogen that causes seasonal epidemics of acute respiratory illness and contributes significantly to childhood pneumonia. Current knowledge and understanding on its patterns of spread, prevalence and persistence in communities in low resource settings is limited.

METHODS

We present findings of a molecular-epidemiological analysis of nasal samples from children < 5 years of age admitted with syndromic pneumonia between 2007 and 2016 to Kilifi County Hospital, coastal Kenya. HMPV infection was detected using real-time RT-PCR and positives sequenced in the fusion (F) and attachment (G) genes followed by phylogenetic analysis. The association between disease severity and HMPV subgroup was assessed using Fisher's exact test.

RESULTS

Over 10 years, 274/6756 (4.1%) samples screened were HMPV positive. Annual prevalence fluctuated between years ranging 1.2 to 8.7% and lowest in the recent years (2014-2016). HMPV detections were most frequent between October of one year to April of the following year. Genotyping was successful for 205/274 (74.8%) positives revealing clades A2b (41.0%) and A2c (10.7%), and subgroups B1 (23.4%) and B2 (24.9%). The dominance patterns were: clade A2b between 2007 and 11, subgroup B1 between 2012 and 14, and clade A2c in more recent epidemics. Subgroup B2 viruses were present in all the years. Temporal phylogenetic clustering within the subgroups for both local and global sequence data was seen. Subgroups occurring in each epidemic season were comprised of multiple variants. Pneumonia severity did not vary by subgroup (p = 0.264). In both the F and G gene, the sequenced regions were found to be predominantly under purifying selection.

CONCLUSION

Subgroup patterns from this rural African setting temporally map with global strain distribution, suggesting a well-mixed global virus transmission pool of HMPV. Persistence in the local community is characterized by repeated introductions of HMPV variants from the global pool. The factors underlying the declining prevalence of HMPV in this population should be investigated.

Time series non-Gaussian Bayesian bivariate model applied to data on HMPV and RSV: a case of Dadaab in Kenya

Background

Human metapneumovirus (HMPV) have similar symptoms to those caused by the respiratory syncytial virus (RSV). The modes of transmission and dynamics of time series data still remain poorly understood. Climatic factors have long been suspected to be implicated in impacting on the number of cases for these epidemics. Currently, only a few models satisfactorily capture the dynamics of time series data of these two viruses. Our objective was to assess the presence of influence of high incidences between the viruses and to ascertain whether higher incidences of one virus are influenced by the other.

Methods

In this study, we used a negative binomial model to investigate the relationship between RSV and HMPV while adjusting for climatic factors. We specifically aimed at establishing the heterogeneity in the autoregressive effect to account for the influence between these viruses.

Results

In this study, our findings showed that RSV incidence contributed to the severity of HMPV incidence. This was achieved through comparison of 12 models with different structures, including those with and without interaction between climatic factors. The models with climatic factors out-performed those without.

Conclusions

The study has improved our understanding of the dynamics of RSV and HMPV in relation to climatic cofactors thereby setting a platform to devise better intervention measures to combat the epidemics. We conclude that preventing and controlling RSV infection subsequently reduces the incidence of HMPV.

Respiratory syncytial virus, human metapneumovirus, and influenza virus infection in Bangkok, 2016-2017

Children and adults residing in densely populated urban centers around the world are at risk of seasonal influenza-like illness caused by respiratory viruses such as influenza virus, human metapneumovirus (hMPV), and respiratory syncytial virus (RSV). In a large metropolitan of Thailand’s capital city Bangkok, most respiratory infections are rarely confirmed by molecular diagnostics. We therefore examined the frequency of RSV, hMPV, and influenza virus in 8,842 patients who presented influenza-like illness and sought medical care at a large hospital in Bangkok between 2016 and 2017. Using a multiplex real-time reverse-transcription polymerase chain reaction (RT-PCR), 30.5% (2,699/8,842) of nasopharyngeal (NP) swab samples tested positive for one or more of these viruses. Influenza virus comprised 17.3% (1,528/8,842), of which the majority were influenza A/H3N2. Such infection was most prevalent among adults and the elderly. RSV was identified in 11.4% (1,011/8,842) and were mostly ON1 and BA9 genotypes. Of the hMPV-positive samples (3.6%, 318/8,842), genotypes A2, B1, and B2 were detected. A small number of individuals experienced co-infections (1.8%, 155/8,842), most commonly between RSV and influenza A/H3N2. RSV and hMPV co-infections were also found, but mainly in young children. Viral respiratory tract infection peaked locally in the rainy season (June to September). These findings support the utility of rapid nucleic acid testing of RSV, hMPV, and influenza virus in patients with ILI.

Comparison of Clinical Characteristics of Human Metapneumovirus and Respiratory Syncytial Virus Infections in Hospitalized Young Children

Human metapneumovirus (HMPV) and respiratory syncytial virus (RSV) are the leading causes of acute respiratory tract infection in children, and clinical manifestations of these virus infections are considered similar. To investigate the differences in clinical characteristics between HMPV and RSV infections in young children, we prospectively enrolled children ＜ 3 years old who required hospitalization with acute respiratory tract infection due to HMPV or RSV at 10 hospitals in Japan. We enrolled 48 children with HMPV infection and 141 with RSV infection. Patients with HMPV infection were older than those with RSV infection. High-grade fever was more frequently observed in patients with HMPV infection, whereas no significant differences in respiratory symptoms were apparent. Abnormal serum lactate dehydrogenase values and consolidation shadows on chest X-ray were more frequently observed in patients with HMPV infection. During hospitalization, nasal mucus suction was more frequently required in patients with RSV infection. On the other hand, β2-adrenergic agonists, corticosteroids, and leukotriene receptor antagonists were more frequently used in patients with HMPV infection. These findings suggest that HMPV and RSV infections show similar respiratory symptoms, but HMPV infection is more likely to lead to the development of pneumonia, at least among hospitalized young children.

Respiratory Virus Infections in Hematopoietic Cell Transplant Recipients

Highly immunocompromised pediatric and adult hematopoietic cell transplant (HCT) recipients frequently experience respiratory infections caused by viruses that are less virulent in immunocompetent individuals. Most of these infections, with the exception of rhinovirus as well as adenovirus and parainfluenza virus in tropical areas, are seasonal variable and occur before and after HCT. Infectious disease management includes sampling of respiratory specimens from nasopharyngeal washes or swabs as well as sputum and tracheal or tracheobronchial lavages. These are subjected to improved diagnostic tools including multiplex PCR assays that are routinely used allowing for expedient detection of all respiratory viruses. Disease progression along with high mortality is frequently associated with respiratory syncytial virus, parainfluenza virus, influenza virus, and metapneumovirus infections. In this review, we discuss clinical findings and the appropriate use of diagnostic measures. Additionally, we also discuss treatment options and suggest new drug formulations that might prove useful in treating respiratory viral infections. Finally, we shed light on the role of the state of immune reconstitution and on the use of immunosuppressive drugs on the outcome of infection.

Human adenovirus in nasopharyngeal and blood samples from children with and without respiratory tract infections

•

Positive HAdV culture and high levels of HAdV DNA >10⁶ copies/mL in NPAs were strongly associated with RTI in hospitalized children.

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Co-detection of other viruses was a very common phenomenon in children with HAdV DNA positive NPAs.

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Qualitative PCR detection of HAdV DNA in NPAs was not useful for diagnostic purposes.

Background

Human adenovirus (HAdV) is a double-stranded DNA virus associated with respiratory tract infections (RTI) in children. Using polymerase chain reaction (PCR) tests, HAdV often is detected together with other virus species, even in healthy controls.

Objectives

The aim of this study was to compare molecular detection of HAdV with culture, and to examine the associations of various methods to RTI.

Study design

Nasopharyngeal aspirates (NPA) were collected from 4319 children admitted with RTI and from 361 controls. The NPAs were examined for 23 viral and bacterial pathogens, using inhouse real-time PCR-assays based on TaqMan probes, in addition to bacterial and viral culture. HAdV concentration was evaluated semi-quantitatively from the Ct-value and quantitatively by use of ADENOVIRUS R-gene®.

Results

HAdV-DNA was detected in 6.1% patient samples and in 10.5% controls (p< 0.001). Compared to controls, patients had an OR of 3.8 (95% CI 1.4–10.3) for mono-detection of HAdV DNA, and an OR of 5.1 (95% CI 2.0–13.4) for HAdV-positive samples grew adenovirus by culture. HAdV DNA loads from children with RTI consisted of two clusters: one cluster with high viral loads (Ct < 30 and >106 copies/ml) and one cluster with low viral loads, whereas among the controls, nearly all had low viral loads (OR 7.8, 95% CI 2.2–27.1). In 61 available plasma samples, 16.4% were positive for HAdV DNA, all were from patients.

Conclusion

The detection of HAdV DNA per se by qualitative PCR is not useful as a diagnostic test. Detection of HAdV by use of viral culture and a high viral HAdV DNA load are the two methods most strongly associated with RTI in children.

Viral pathogens associated with acute lower respiratory tract infections in children younger than 5 years of age in Bulgaria

Acute lower respiratory infections (ALRIs) are a leading cause of morbidity and hospital admissions in children. This study aimed to determine the viral etiology of these infections in children aged < 5 years during three successive epidemic seasons in Bulgaria. Nasopharyngeal and throat specimens were collected from children with bronchiolitis and pneumonia during the 2015/2016, 2016/2017, and 2017/2018 seasons. The viral etiology was determined by individual real-time PCR assays against 11 respiratory viruses. Of the 515 children examined, 402 (78.1%) were positive for at least one virus. Co-infections with two and three viruses were found in 64 (15.9%) of the infected children. Respiratory syncytial virus (RSV) was the predominant pathogen (37.5%), followed by rhinoviruses (13.8%), metapneumovirus (9.1%), adenoviruses (7%), bocaviruses (7%), influenza A(H1N1)pdm09 (4.9%), A(H3N2) (4.3%), type B (4.1%), and parainfluenza viruses 1/2/3 (2.9%). RSV-B were more prevalent than RSV-A during the three seasons. At least one respiratory virus was identified in 82.6% and 70.1% of the children with bronchiolitis and pneumonia, respectively. Respiratory viruses, especially RSV, are principal pathogens of ALRIs in children aged < 5 years. Diagnostic testing for respiratory viruses using molecular methods may lead to the reduced use of antibiotics and may assist in measures to control infection.

Burden of Human Metapneumovirus and Respiratory Syncytial Virus Infections in Asthmatic Children

BACKGROUND

Human metapneumovirus (hMPV) and respiratory syncytial virus (RSV) are the leading causes of acute respiratory illness in children. Clinical burden of each infection on the respiratory distress in asthmatic patients remains unclear. The purpose of the study was to clarify the effect of these infections on the severity of asthmatic children in the seasonal outbreaks.

METHODS

A total of 1,217 pediatric inpatients with hMPV (n = 114) or RSV (n = 1,103) infection in Yamaguchi prefecture, Japan, between 2011 and 2014 were enrolled. Bronchial asthma was defined as having more than 3 episodes of wheezing illness over 1 year of age. Infection was determined by the positive antigen test for each virus in the nasal specimens.

RESULTS

The number of patients peaked at age 12-15 months in hMPV infection and at age 0-3 months in RSV infection. The proportion of hypoxic patients (40-50%) did not differ at any age between hMPV-infected and RSV-infected children. In the analysis of date from > 1 year old patients with hypoxia, hMPV-infection group was older (P = 0.036), and more frequently had history of asthma (P = 0.015) or abnormal chest roentgenogram (P < 0.001) than RSV-infection group. Multivariate analysis indicated that the hypoxia-associated factors were history of asthma in both hMPV (odds ratio [OR]: 15.8; P < 0.001) and RSV infections (OR, 2.2; P = 0.005), higher body temperature in hMPV infection (OR, 2.2; P = 0.009), and younger age in RSV infection (OR, 1.4; P = 0.004).

CONCLUSIONS

Outbreaks of hMPV, rather than, RSV infection may have a greater impact on the development of hypoxic respiratory illness in asthmatic children.

Prophylactic and therapeutic approaches for human metapneumovirus

Human metapneumovirus (HMPV) is an important pneumovirus which causes acute respiratory disease in human beings. The viral infection leads to mild to severe respiratory symptoms depending on the age and immune status of the infected individual. Several groups across the world are working on the development of immunogens and therapy to manage HMPV infection with promising results under laboratory conditions but till date any virus specific vaccine or therapy has not been approved for clinical use. This minireview gives an overview of the prophylactic and therapeutic approaches to manage HMPV infections.

Interferon-Mediated Response to Human Metapneumovirus Infection

Human metapneumovirus (HMPV) is one of the leading causes of respiratory diseases in infants and children worldwide. Although this pathogen infects mainly young children, elderly and immunocompromised people can be also seriously affected. To date, there is no commercial vaccine available against it. Upon HMPV infection, the host innate arm of defense produces interferons (IFNs), which are critical for limiting HMPV replication. In this review, we offer an updated landscape of the HMPV mediated-IFN response in different models as well as some of the defense tactics employed by the virus to circumvent IFN response.

High antibiotic prescription rates in hospitalized children with human metapneumovirus infection in comparison to RSV infection emphasize the value of point-of-care diagnostics

BACKGROUND

Respiratory infections are the main causes for hospitalization in children and a common reason for the initiation of antibiotic treatment. Rapid antigen detection tests and point-of-care mPCR-based assays provide a fast detection of viral pathogens. Nonetheless, the prescription rate of antibiotics for respiratory infections is exceedingly high. In particular, human metapneumovirus (hMPV) infections frequently cause antibiotic treatment.

METHODS

Children hospitalized in our clinic with an acute respiratory infection between January 2008 and January 2013 were included in the present study. Data of 3799 children were analyzed retrospectively for clinical symptoms, laboratory findings, and antibiotic and inhalation treatment. We performed an in-house m-RT-PCR-ELISA method for pathogen detection.

RESULTS

Pathogen detection was possible in 2464 patients. In 6.3%, hMPV and, in 24.0%, RSV were detected. Patients positively tested for hMPV received inhalation therapy in 62.9%; patients positive for RSV in 73.8%. Patients positive for hMPV were treated with antibiotics in 62.3%. Patients with RSV infection received antibiotic treatment in 44.4%; all others in 43.5%. Notably, a positive result in RSV-RADT was associated with reduced number of antibiotic treatment.

CONCLUSION

hMPV infections inherit a two times higher probability of antibiotic treatment. There was no significant difference in laboratory findings or body temperature between hMPV infection and infections caused by other pathogens. Clinical symptoms seem not to differ from those in RSV illness. Nonetheless, RSV infections triggered significantly lower antibiotic prescription rates. A considerate application of a POC-mPCR for patients with RSV-like symptoms and age of 1 year and older with a negative RSV-RADT might lead to higher detection rates of hMPV and a reduction in prescription of antibiotics.

Comparative analysis of miRNA profile in human dendritic cells infected with respiratory syncytial virus and human metapneumovirus

OBJECTIVE

Human metapneumovirus (HMPV) and respiratory syncytial virus (RSV) are responsible for respiratory diseases, mostly in children. Despite the clinical and epidemiological similarities between these two pneumoviruses, they elicit different immune responses. This work aims to further our understanding of the differential immune response induced by these respiratory viruses by determining the changes of small non-coding RNAs (miRNAs), which regulate gene expression and are involved in numerous cellular processes including the immune system.

RESULTS

In the present study, we analyzed the expression of miRNA transcripts of human dendritic cells infected with RSV or HMPV by high throughput sequencing using Illumina sequencing technology. Further validation of miRNA expression by quantitative polymerase chain reaction indicated that HMPV infection up-regulated the expression of 2 miRNAs (hsa-miR-182-5p and hsa-miR-4634), while RSV infection induced significant expression of 3 miRNAs (hsa-miR-4448, hsa-miR-30a-5p and hsa-miR-4634). The predominant miRNA induced by both viruses was hsa-miR-4634.

Epidemiological and clinical features of human metapneumovirus in hospitalised paediatric patients with acute respiratory illness: a cross-sectional study in Southern China, from 2013 to 2016

OBJECTIVES

Human metapneumovirus (HMPV) is one of the most important respiratory viral pathogens affecting infants and children worldwide. Our study describes the epidemiological and clinical characteristics of HMPV present in patients hospitalised with acute respiratory illness (ARI) in Guangzhou, Southern China.

STUDY DESIGN

A cross-sectional study.

SETTING

Two tertiary hospitals in Guangzhou.

PARTICIPANTS AND METHODS

Throat swabs were collected over a 3-year period from 5133 paediatric patients (≤14 years) hospitalised with ARI. Patients who are HMPV positive with clinical presentations (101/103) were recorded for further analysis.

RESULTS

Of the 5133 patients included in the study, 103 (2.0%) were positive for HMPV. HMPV was more prevalent in children ≤5 years (2.2%, 98/4399) compared with older children (>5-14 years) (0.7%, 5/734) (P=0.004). Two seasonal HMPV peaks were observed each year and mainly occurred in spring and early summer. Overall, 18.4% (19/103) of patients who are HMPV positive were codetected with other pathogens, most frequently respiratory syncytial virus (36.8%, 7/19). Patients who are HMPV positive presented with a wide spectrum of clinical features, including cough (100.0%, 101/101), abnormal pulmonary breath sound (91.1%, 92/101), fever (88.1%, 89/101), expectoration (77.2%, 78/101), coryza (50.5%, 51/101) and wheezing (46.5%, 47/101). The main diagnosis of patients who are HMPV positive was bronchopneumonia (66.7%, 56/84). Fever (≥38˚C) (91.6%, 76/83) was detected more often in patients with only HMPV detected than in patients with HMPV plus other pathogen(s) detected (72.2%, 13/18) (P=0.037), whereas diarrhoea was more common in patients with HMPV plus other pathogen(s) detected (22.2%, 4/18), compared with patients with HMPV only (3.6%, 3/83) (P=0.018).

CONCLUSIONS

HMPV is an important respiratory pathogen in children with ARI in Guangzhou, particularly in children ≤5 years old. HMPV has a seasonal variation. Bronchopneumonia is a major diagnosis in patients who are HMPV positive.

The Burden of Human Metapneumovirus and Respiratory Syncytial Virus Infections in Hospitalized Norwegian Children

Background

The burden of severe human metapneumovirus (HMPV) respiratory tract infections (RTIs) in European children has not been clarified. We assessed HMPV in Norwegian children and compared hospitalization rates for HMPV and respiratory syncytial virus (RSV).

Methods

We prospectively enrolled children (<16 years old) hospitalized with RTI and asymptomatic controls (2006-2015). Nasopharyngeal aspirate samples were analyzed with polymerase chain reaction (PCR) tests for HMPV, RSV, and 17 other pathogens. We genotyped HMPV-positive samples and assessed shedding time in 32 HMPV-infected children.

Results

In children with RTI, HMPV was detected in 7.3% (267 of 3650) and RSV in 28.7% (1048 of 3650). Among controls, 2.1% (7 of 339) had low HMPV levels detected by PCR, but all were culture negative. HMPV primarily occurred from January to April and in regular epidemics. At least 2 HMPV subtypes occurred each season. The average annual hospitalization rates in children <5 years old with lower RTI were 1.9/1000 (HMPV) and 10.4/1000 (RSV). Among children with RTI, the median HMPV shedding time by PCR was 13 days (range, 6-28 days), but all were culture negative (noninfectious) after 13 days.

Conclusions

HMPV appears in epidemics in Norwegian children, with a hospitalization rate 5 times lower than RSV. Low levels of HMPV are rarely detected in healthy children.