Human metapneumovirus genotypes and severity of disease in young children (n = 100) during a 7-year study in Dijon hospital, France

Distinct roles for type I and type III interferons in virulent human metapneumovirus pathogenesis

Human metapneumovirus (HMPV) is an important cause of acute lower respiratory infection in children and adults worldwide. There are four genetic subgroups of HMPV and both neutralizing antibodies and T cells contribute to protection. However, little is known about mechanisms of pathogenesis and most published work is based on a few extensively passaged, laboratory-adapted strains of HMPV. In this study, we isolated and characterized a panel of low passage HMPV clinical isolates representing all four genetic subgroups. The clinical isolates exhibited lower levels of in vitro replication compared to a lab-adapted strain. We compared disease phenotypes using a well-established mouse model. Several virulent isolates caused severe weight loss, lung pathology, airway dysfunction, and fatal disease in mice, which was confirmed in three inbred mouse strains. Disease severity did not correlate with lung viral titer, as virulent strains exhibited restricted replication in the lower airway. Virulent HMPV isolates were associated with markedly increased proinflammatory cytokine production and neutrophil influx; however, depletion of neutrophils or genetic ablation of inflammasome components did not reverse disease. Virulent clinical isolates induced markedly increased type I and type III interferon (IFN) secretion in vitro and in vivo. STAT1/2-deficient mice lacking both type I and type III IFN signaling showed reduced disease severity and increased lung viral replication. Inhibition of type I IFN signaling using a blocking antibody or genetic ablation of the type I IFN receptor reduced pathology with minimal effect on viral replication. Conversely, blockade of type III IFN signaling with a neutralizing antibody or genetic ablation of the IFN-lambda receptor had no effect on pathogenesis but restored viral replication. Collectively, these results demonstrate distinct roles for type I and type III IFN in HMPV pathogenesis and immunity.

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.

Molecular typing and epidemiologic profiles of human metapneumovirus infection among children with severe acute respiratory infection in Huzhou, China

Background

Human metapneumovirus (hMPV) is one of the important pathogens in infant respiratory tract infection. However, the molecular epidemiology of hMPV among children < 14 years of age hospitalized with severe acute respiratory infection (SARI) is unclear. We investigated the hMPV infection status and genotypes of children hospitalized with SARI from January 2016 to December 2020 in Huzhou, China.

Methods

A nasopharyngeal flocked swab, nasal wash, or nasopharyngeal swab/or opharyngeal swab combination sample was collected from children with SARI in Huzhou from January 2016 to December 2020. Quantitative reverse transcription-polymerase chain reaction was performed to detect hMPV RNA. The hMPV F gene was amplified and sequenced, followed by analysis using MEGA software (ver. 7.0). Epidemiological data were analyzed using Microsoft Excel 2010 and SPSS (ver. 22.0) software.

Results

A total of 1133 children with SARI were recruited from 2016 to 2020. Among them, 56 (4.94%) were positive for hMPV-RNA. Children < 5 years of age accounted for 85.71% of the positive cases. The hMPV incidence was high in spring and winter, especially in December and January to March. Phylogenetic analysis of the F-gene sequences of 28 hMPV strains showed that the A1, B1, and B2 genotypes were prevalent in Huzhou, and the dominant hMPV genotype varied according to surveillance year.

Conclusions

HMPV is an important respiratory pathogen in children in Huzhou, with a high incidence in winter and spring in children < 5 years of age. In this study, genotypes A1, B1, and B2 were the most prevalent.

Epidemiology of Human Metapneumovirus-associated Lower Respiratory Tract Infections in African Children: Systematic Review and Meta-analysis

BACKGROUND

Human metapneumovirus (hMPV) has been associated with upper and lower respiratory tract infections (LRTI) in children and adults. This systematic review evaluated the epidemiology of hMPV-associated LRTI, including severe acute respiratory infection (SARI) hospitalization or clinically diagnosed severe pneumonia, in African children under 5 years of age.

METHODS

We searched Science Direct, PubMed, Cochrane Central, Scopus, and WHO regional databases using the terms "("Human metapneumovirus" AND "Africa") OR ("hMPV" AND "Africa")" up to September 17, 2020. Other sources included ClinicalTrials.gov to obtain unpublished data. Studies were included if children were less than 5 years of age and hospitalized with hMPV-associated LRTI, SARI or if clinically diagnosed with severe pneumonia in the community. The main outcomes were prevalence of hMPV identified among children with hospitalized LRTI or SARI. We further calculated odds ratios for hMPV in cases with LRTI compared with non-LRTI controls. Pooled results were calculated using a random-effects model.

RESULTS

Thirty studies were eligible for inclusion in the review. The prevalence of hMPV-LRTI/SARI among hospitalized and severe pneumonia cases was 4.7% [95% confidence interval (CI): 3.9-5.6, I2 = 95.0]. The case-control studies indicated that hMPV was 2.0-fold (95% CI: 0.9-4.4) more likely to be identified in LRTI cases (10.3%) than controls (6.0%). Three of 5 studies reported hMPV-associated LRTI case fatality risk, with a pooled estimate of 1.3% (95% CI: 0.3-2.9; I2 = 49).

CONCLUSIONS

hMPV was associated with approximately 5% of LRTI/SARI hospitalizations or severe pneumonia cases in Africa.

Host Components That Modulate the Disease Caused by hMPV

Human metapneumovirus (hMPV) is one of the main pathogens responsible for acute respiratory infections in children up to 5 years of age, contributing substantially to health burden. The worldwide economic and social impact of this virus is significant and must be addressed. The structural components of hMPV (either proteins or genetic material) can be detected by several receptors expressed by host cells through the engagement of pattern recognition receptors. The recognition of the structural components of hMPV can promote the signaling of the immune response to clear the infection, leading to the activation of several pathways, such as those related to the interferon response. Even so, several intrinsic factors are capable of modulating the immune response or directly inhibiting the replication of hMPV. This article will discuss the current knowledge regarding the innate and adaptive immune response during hMPV infections. Accordingly, the host intrinsic components capable of modulating the immune response and the elements capable of restricting viral replication during hMPV infections will be examined.

Phylogenetic analysis and circulation pattern of human metapneumovirus strains in children with acute respiratory infection in Iran, 2014–2015

Aim: The aim of the present study was to investigate the prevalence and genetic variation of the human metapneumovirus (HMPV) G gene in children less than 8 years old with acute respiratory tract infections in Iran during 2014–2015. Materials & methods: To this end, 110 nasal swabs were tested for HMPV F gene. All positive samples were tested for the full length of HMPV G gene, then sequenced and analyzed for phylogenetic grouping. Results: Six (5.45%) out of 110 samples were positive for HMPV gene. Our HMPV sequences clustered into two main clusters: A2b (five isolates) and B1 (one isolate). The dN/dS ratio showed the presence of negative selective pressure. Conclusion: A2b was the predominant genotype during the study period in southwest of Iran.

Experiments Investigating the Competitive Growth Advantage of Two Different Genotypes of Human Metapneumovirus: Implications for the Alternation of Genotype Prevalence

Human metapneumovirus (hMPV) is an important pathogen that causes upper and lower respiratory tract infections in children worldwide. hMPV has two major genotypes, hMPV-A and hMPV-B. Epidemiological studies have shown that the two hMPV genotypes alternate in predominance worldwide in recent years. Co-circulation of the two genotypes of hMPV was usually observed and there is no study about the interaction between them, such as competitive replication, which maybe the possible mechanisms for alternating prevalence of subtypes. Our present study have used two different genotypes of hMPV (genotype A: NL/1/00; B: NL/1/99) in different proportions in animal model (BALB/c mice) and cell model (Vero-E6) separately. The result showed that the competitive growth does exist in BALB/c mice, genotype B had a strong competitive advantage. However, genotype B did not cause more severe disease than non-predominant (genotype A) or mixed strains in the study, which were evaluated by the body weight, airway hyperresponsiveness and lung pathology of mouse. In cell model, competitive growth and the two genotypes alternately prevalence were observed. In summary, we confirmed that there was a competitive replication between hMPV genotype A and B, and no difference in disease severity caused by the two subtypes. This study shows a new insight to understand the alternation of hMPV genotype prevalence through genotype competition and provide experimental evidence for disease control and vaccine design.

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.

Genetic characterization of human metapneumovirus identified through community and facility-based surveillance of infants in Dhaka, Bangladesh

BACKGROUND

Acute respiratory infection (ARI) is a leading cause of morbidity and mortality in children in low and middle-income countries. Human metapneumovirus (hMPV) is one of the most common viral etiological agents for ARIs in children.

OBJECTIVES

In this study, we explored the genotypic diversity and the epidemiology of hMPV among infants in Dhaka, Bangladesh.

STUDY DESIGN

Between December 2014 and August 2016, a total of 3810 mid-turbinate nasal swab samples were collected from infants (0 to 6 months of age) who met clinical ARI criteria, as a part of a prospective ARI cohort study. hMPV was detected using polymerase chain reaction, and genotyped by sequencing and phylogenetic analysis.

RESULTS

hMPV was identified in 206 (5.4%) nasal swab specimens. One-tenth of the hMPV-positive swabs (n = 19) were also positive for other respiratory viruses. hMPV activity peaked in January and September in 2015; however, no seasonal pattern of hMPV infection was detected. Phylogenetic analyses of the N and F gene-fragments revealed that the hMPV strains circulating in Dhaka, Bangladesh, belonged to three genotypes: A2b, A2c, and B1. Genotype A (57%) was the predominant hMPV genotype circulating in Bangladesh during the study period.

CONCLUSION

This study describes both the epidemiology of hMPV infection and its genotypic strain diversity in Dhaka, Bangladesh.

The role of human Metapneumovirus genetic diversity and nasopharyngeal viral load on symptom severity in adults

Background

Human metapneumovirus (HMPV) is established as one of the causative agents of respiratory tract infections. To date, there are limited reports that describe the effect of HMPV genotypes and/or viral load on disease pathogenesis in adults. This study aims to determine the role of HMPV genetic diversity and nasopharyngeal viral load on symptom severity in outpatient adults with acute respiratory tract infections.

Methods

Severity of common cold symptoms of patients from a teaching hospital was assessed by a four-category scale and summed to obtain the total symptom severity score (TSSS). Association between the fusion and glycoprotein genes diversity, viral load (quantified using an improved RT-qPCR assay), and symptom severity were analyzed using bivariate and linear regression analyses.

Results

Among 81/3706 HMPV-positive patients, there were no significant differences in terms of demographics, number of days elapsed between symptom onset and clinic visit, respiratory symptoms manifestation and severity between different HMPV genotypes/sub-lineages. Surprisingly, elderly patients (≥65 years old) had lower severity of symptoms (indicated by TSSS) than young and middle age adults (p = 0.008). Nasopharyngeal viral load did not correlate with nor predict symptom severity of HMPV infection. Interestingly, at 3–5 days after symptom onset, genotype A-infected patients had higher viral load compared to genotype B (4.4 vs. 3.3 log₁₀ RNA copies/μl) (p = 0.003).

Conclusions

Overall, HMPV genetic diversity and viral load did not impact symptom severity in adults with acute respiratory tract infections. Differences in viral load dynamics over time between genotypes may have important implications on viral transmission.

Electronic supplementary material

The online version of this article (10.1186/s12985-018-1005-8) contains supplementary material, which is available to authorized users.

Chest radiographic features of human metapneumovirus infection in pediatric patients

BACKGROUND

Human metapneumovirus (HMPV) was identified in 2001 and is a common cause of acute respiratory illness in young children. The radiologic characteristics of laboratory-confirmed HMPV acute respiratory illness in young children have not been systematically assessed.

OBJECTIVE

We systematically evaluated the radiographic characteristics of acute respiratory illness associated with HMPV in a prospective cohort of pediatric patients.

MATERIALS AND METHODS

We included chest radiographs from children <5 years old with acute respiratory illness who were enrolled in the prospective New Vaccine Surveillance Network (NVSN) study from 2003 to 2009 and were diagnosed with HMPV by reverse transcription-polymerase chain reaction (RT-PCR). Of 215 HMPV-positive subjects enrolled at our tertiary care children's hospital, 68 had chest radiographs obtained by the treating clinician that were available for review. Two fellowship-trained pediatric radiologists, independently and then in consensus, retrospectively evaluated these chest radiographs for their radiographic features.

RESULTS

Parahilar opacities were the most commonly observed abnormality, occurring in 87% of children with HMPV. Hyperinflation also occurred frequently (69%). Atelectasis (40%) and consolidation (18%) appeared less frequently. Pleural effusion and pneumothorax were not seen on any radiographs.

CONCLUSION

The clinical presentations of HMPV include bronchiolitis, croup and pneumonia. Dominant chest radiographic abnormalities include parahilar opacities and hyperinflation, with occasional consolidation. Recognition of the imaging patterns seen with common viral illnesses like respiratory syncytial virus (RSV) and HMPV might facilitate diagnosis and limit unnecessary antibiotic treatment.

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.

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

BACKGROUND

It is unclarified as to whether viral co-detection and human metapneumovirus (HMPV) genotypes relate to clinical manifestations in children with HMPV and lower respiratory tract infection (LRTI), and if the clinical course and risk factors for severe LRTI differ between HMPV and respiratory syncytial virus (RSV).

METHODS

We prospectively enrolled hospitalized children aged <16 years with LRTI from 2006 to 2015. Children were clinically examined, and nasopharyngeal aspirates were analyzed using semi-quantitative, real-time polymerase chain reaction tests for HMPV, RSV and 17 other pathogens. HMPV-positive samples were genotyped.

RESULTS

A total of 171 children had HMPV infection. HMPV-infected children with single virus (n = 106) and co-detections (n = 65) had similar clinical manifestations. No clinical differences were found between HMPV genotypes A (n = 67) and B (n = 80). The HMPV-infected children were older (median 17.2 months) than RSV-infected children (median 7.3 months, n = 859). Among single virus-infected children, no differences in age-adjusted LRTI diagnoses were found between HMPV and RSV. Age was an important factor for disease severity among single virus-infected children, where children <6 months old with HMPV had a milder disease than those with RSV, while in children 12-23 months old, the pattern was the opposite. In multivariable logistic regression analysis for each virus type, age ≥12 months (HMPV), and age <6 months (RSV), prematurity, ≥1 chronic disease and high viral loads of RSV, but not high HMPV viral loads, were risk factors for severe disease.

CONCLUSIONS

Among hospitalized children with LRTI, HMPV manifests independently of viral co-detections and HMPV genotypes. Disease severity in HMPV- and RSV-infected children varies in relation to age. A history of prematurity and chronic disease increases the risk of severe LRTI among HMPV- and RSV-infected children.

Metapneumovirus Infections and Respiratory Complications

Acute respiratory tract infections (ARTIs) are the most common illnesses experienced by people of all ages worldwide. In 2001, a new respiratory pathogen called human metapneumovirus (hMPV) was identified in respiratory secretions. hMPV is an RNA virus of the Paramyxoviridae family, and it has been isolated on every continent and from individuals of all ages. hMPV causes 7 to 19% of all cases of ARTIs in both hospitalized and outpatient children, and the rate of detection in adults is approximately 3%. Symptoms of hMPV infection range from a mild cold to a severe disease requiring a ventilator and cardiovascular support. The main risk factors for severe disease upon hMPV infection are the presence of a high viral load, coinfection with other agents (especially human respiratory syncytial virus), being between 0 and 5 months old or older than 65 years, and immunodeficiency. Currently, available treatments for hMPV infections are only supportive, and antiviral drugs are employed in cases of severe disease as a last resort. Ribavirin and immunoglobulins have been used in some patients, but the real efficacy of these treatments is unclear. At present, the direction of research on therapy for hMPV infection is toward the development of new approaches, and a variety of vaccination strategies are being explored and tested in animal models. However, further studies are required to define the best treatment and prevention strategies.

Human metapneumovirus in patients hospitalized with acute respiratory infections: A meta-analysis

This meta-analysis aimed to estimate the prevalence of human metapneumovirus (hMPV) infections in patients hospitalized for acute respiratory infection (ARI) and to study factors associated with this prevalence. Medline and ScienceDirect databases were searched for prospective observational studies that screened hospitalized patients with ARI for hMPV by RT-PCR, with data available at December 27, 2014. The risk of bias was assessed regarding participation rate, definition of ARI, description of diagnostic technique, method of inclusion identical for all subjects, standardized and identical sampling method for all subjects, analysis performed according to the relevant subgroups, and presentation of data sources. Random-effect meta-analysis with arcsine transformation and meta-regressions was used. In the 75 articles included, the prevalence of hMPV among hospitalized ARI was 6.24% (95% CI 5.25-7.30). An effect of the duration of the inclusion period was observed (p=0.0114), with a higher prevalence of hMPV in studies conducted during periods of 7-11 months (10.56%, 95% CI 5.97-16.27) or complete years (7.55%, 95% CI 5.90-9.38) than in periods of 6 months or less (5.36%, 95% CI 4.29-6.54). A significant increase in the incidence with increasing distance from the equator was observed (p=0.0384). hMPV should be taken into account as a possible etiology in hospitalized ARI.

Circulation of human metapneumovirus among children with influenza-like illness in Wuhan, China

Human metapneumovirus (HMPV) is a worldwide distributed pathogen of the respiratory tract. The objectives of this study were to identify HMPV infections among children with influenza‐like illness (ILI) in Wuhan and to assess circulation patterns and molecular diversity of HMPV in this area. From July 2008 to December 2013, a total of 3,883 throat swab samples were collected from ILI outpatients under 16 years old. HMPV RNA was detected in 171 samples (4.40%). All the four subtypes of HMPV were identified, among which A2 was the most common subtype (61/145, 42.1%), followed by B1, B2, and A1. During the study period, HMPV circulation presented a biennial alternation between high and low incidence in Wuhan and the seasonal peak also shift between winter and spring in two continuous seasons. Subtype A2, B1, and B2 co‐circulated during the study period, with genotype A prevailing in epidemic season 2008–2009 and 2012–2013, and genotype B prevailing during other periods. This large‐scale analysis of HMPV prevalence in ILI outpatient children improves the understanding of local HMPV circulation patterns and provides molecular epidemic evidence for comparative analysis of HMPV infection. J. Med. Virol. 88:774–781, 2016. © 2015 Wiley Periodicals, Inc.

Human Metapneumovirus Infection in Jordanian Children: Epidemiology and Risk Factors for Severe Disease

BACKGROUND

Human metapneumovirus (HMPV) is a leading cause of acute respiratory tract infection in young children. Our objectives were to define HMPV epidemiology and circulating strains and determine markers of severe disease in Jordanian children.

METHODS

We conducted a prospective study from March 16, 2010 to March 31, 2013 using quantitative reverse transcription-polymerase chain reaction to determine the frequency of HMPV infection among children <2 years old admitted with fever and/or acute respiratory illness to a major government hospital in Amman, Jordan.

RESULTS

HMPV was present in 273 of 3168 (8.6%) of children presenting with acute respiratory tract infection. HMPV A2, B1 and B2, but not A1, were detected during the 3-year period. HMPV-infected children were older and more likely to be diagnosed with bronchopneumonia than HMPV-negative children. HMPV-infected children with lower respiratory tract infection had higher rates of cough and shortness of breath than children with lower respiratory tract infection infected with other or no identifiable viruses. Symptoms and severity were not different between children with HMPV only compared with HMPV coinfection. Children with HMPV subgroup A infection were more likely to require supplemental oxygen. In a multivariate analysis, HMPV subgroup A and age <6 months were independently associated with supplemental oxygen requirement.

CONCLUSIONS

HMPV is a leading cause of acute respiratory tract disease in Jordanian children <2 years old. HMPV A and young age were associated with severe disease. Ninety percent of HMPV-infected hospitalized children were full term and otherwise healthy, in contrast to high-income nations; thus, factors contributing to disease severity likely vary depending on geographic and resource differences.

Clinical features of human metapneumovirus genotypes in children with acute lower respiratory tract infection in Changsha, China

To explore the epidemiological and clinical features of different human metapneumovirus (hMPV) genotypes in hospitalized children. Reverse transcription polymerase chain reaction (RT‐PCR) or PCR was employed to screen for both hMPV and other common respiratory viruses in 2613 nasopharyngeal aspirate specimens collected from children with lower respiratory tract infections from September 2007 to February 2011 (a period of 3.5 years). The demographics and clinical presentations of patients infected with different genotypes of hMPV were compared. A total of 135 samples were positive for hMPV (positive detection rate: 5.2%). Co‐infection with other viruses was observed in 45.9% (62/135) of cases, and human bocavirus was the most common additional respiratory virus. The most common symptoms included cough, fever, and wheezing. The M gene was sequenced for 135 isolates; of these, genotype A was identified in 72.6% (98/135) of patients, and genotype B was identified in 27.4% (37/135) of patients. The predominant genotype of hMPV changed over the 3.5‐year study period from genotype A2b to A2b or B1 and then to predominantly B1. Most of clinical features were similar between patients infected with different hMPV genotypes. These results suggested that hMPV is an important viral pathogen in pediatric patients with acute lower respiratory tract infection in Changsha. The hMPV subtypes A2b and B1 were found to co‐circulate. The different hMPV genotypes exhibit similar clinical characteristics. J. Med. Virol. 87:1839–1845, 2015. © 2015 Wiley Periodicals, Inc.

Effect of in vitro syncytium formation on the severity of human metapneumovirus disease in a murine model

Human metapneumovirus (HMPV) is an important cause of acute respiratory tract infections (ARTI) in children, elderly individuals and immunocompromised patients. In vitro, different HMPV strains can induce variable cytopathic effects ranging from large multinucleated syncytia to focal cell rounding. In this study, we investigated the impact of different in vitro phenotypes of two HMPV strains on viral replication and disease severity in a BALB/c mouse model. We first generated two recombinant GFP-expressing HMPV viruses: C-85473, a syncytium-inducing strain (rC-85473) belonging to the A1 subtype and CAN98-75, a focal cell rounding-inducing strain (rCAN98-75) of the B2 subtype. We subsequently exchanged the F genes of both strains to create the chimeric viruses rC-85473_F and rCAN98-75_F. We demonstrated that the F protein was the sole protein responsible for the syncytium phenotype and that viruses carrying a syncytium-inducing F protein replicated to significantly higher titers in vitro. In vivo, however, the virulence and replicative capacity of the different HMPV strains did not appear to be solely dependent on the F gene but also on the viral background, with the strains containing the C-85473 background inducing more weight loss as well as increased lung viral titers, pro-inflammatory cytokines and inflammation than strains containing the CAN98-75 background. In conclusion, the F protein is the main determinant of syncytium formation and replication kinetics in vitro, although it is not the only factor implicated in HMPV disease severity in mice.

Phylogenetic analysis of human metapneumovirus detected in hospitalized patients in Kuwait during the years 2009-2011

BACKGROUND

Human metapneumovirus (hMPV) is an important cause of both upper and lower respiratory tract infections (RTIs) in all age groups. Children, elderly, and immunocompromised individuals are the most affected groups. HMPV infection accounts for 5% of hospitalized patients with respiratory tract infections in Kuwait. It is mostly detected among infants and elderly age groups, and both hMPV genotypes A and B circulate in Kuwait.

METHODS

In this study, the genetic diversity of detected hMPV was evaluated, and a phylogenetic analysis based on partial nucleotide and amino acid sequences of the G gene was performed for hMPV detected among hospitalized patients with RTIs.

RESULTS

Our results showed that 62% of hMPV sequences belonged to the A genotype and 38% to the B genotype. A2b and B2 subtypes were detected and circulated during the study period, whereas A1 and B1 subtypes were not detected. Based on nucleotide sequences of the G gene, most of hMPV strains (57%) were clustered with Indian strains, followed by Greek strains (24%) and Canadian strains (14%). One strain (5%) clustered within the B genotype but had different branches than B1 and B2 branches.

CONCLUSION

Our data showed the co-circulation of hMPV genotypes A2b and B2 in Kuwait with genetic diversity suggestive of evolution through negative selection.

Identification of new respiratory viruses in the new millennium

The rapid advancement of molecular tools in the past 15 years has allowed for the retrospective discovery of several new respiratory viruses as well as the characterization of novel emergent strains. The inability to characterize the etiological origins of respiratory conditions, particularly in children, led several researchers to pursue the discovery of the underlying etiology of disease. In 2001, this led to the discovery of human metapneumovirus (hMPV) and soon following that the outbreak of Severe Acute Respiratory Syndrome coronavirus (SARS-CoV) promoted an increased interest in coronavirology and the latter discovery of human coronavirus (HCoV) NL63 and HCoV-HKU1. Human bocavirus, with its four separate lineages, discovered in 2005, has been linked to acute respiratory tract infections and gastrointestinal complications. Middle East Respiratory Syndrome coronavirus (MERS-CoV) represents the most recent outbreak of a completely novel respiratory virus, which occurred in Saudi Arabia in 2012 and presents a significant threat to human health. This review will detail the most current clinical and epidemiological findings to all respiratory viruses discovered since 2001.

Human metapneumovirus viral load is an important risk factor for disease severity in young children

BACKGROUND

The role of viral load in human metapneumovirus (HMPV) disease severity has not yet been clearly determined.

OBJECTIVE

We evaluated the importance of viral load along with other factors in HMPV disease severity among children aged <3 years old.

STUDY DESIGN

HMPV-positive cases were selected from a cohort of outpatients and hospitalized children with lower respiratory tract infections. HMPV groups (A or B) and viral loads were determined in their nasopharyngeal aspirates. Disease severity was defined by assessing risk for hospitalization and by using two validated clinical severity scores.

RESULTS

Of the 118 HMPV cases detected over 4 years for which viral load could be determined, 60 belonged to genotype A and 58 to genotype B. Baseline characteristics were similar in HMPV-A and HMPV-B mono-infected patients. In multivariate analysis, HMPV hospitalization was associated with viral load ≥1000 copies/10(4)cells (OR, 3.2; 95%CI, 1.4-7.4), age <6 months (OR, 3.1; 95%CI, 1.2-8.6) and presence of ≥3 children in the household (OR, 2.7; 95%CI, 1.04-6.9). A high HMPV viral load was also associated with pulmonary rales (p=.03), use of bronchodilators (p=.02) and inhaled corticosteroids (p=.01).

CONCLUSION

HMPV viral load is associated with disease severity in young children along with young age and household crowding.

Human metapneumovirus: insights from a ten-year molecular and epidemiological analysis in Germany

Human metapneumovirus (HMPV) is a cause of respiratory tract illness at all ages. In this study the epidemiological and molecular diversity among patients of different ages was investigated. Between 2000-2001 and 2009-2010, HMPV was detected in 3% (138/4,549) of samples from outpatients with influenza-like illness with a new, sensitive real-time RT-PCR assay. Several hundred (797) clinical specimens from hospitalized children below the age of 4 years with acute respiratory illness were investigated and HMPV was detected in 11.9% of them. Investigation of outpatients revealed that HMPV infections occurred in individuals of all ages but were most prevalent in children (0-4 years) and the elderly (>60 years). The most present clinical features of HMPV infections were cough, bronchitis, fever/shivers and pneumonia. About two thirds of HMPV-positive samples were detected in February and March throughout the study period. Molecular characterization of HMPV revealed a complex cyclic pattern of group dominance where HMPV subgroup A and B viruses predominated in general for three consecutive seasons. German HMPV represented all genetic lineages including A1, A2, B1, B2, sub-clusters A2a and A2b. For Germany, not only time-dependent circulation of lineages and sub-clusters was observed but also co-circulation of two or three predominant lineages. Two newly emerging amino acid substitutions (positions 223 and 280) of lineage B2 were detected in seven German HMPV sequences. Our study gives new insights into the molecular epidemiology of HMPV in in- and outpatients over a time period of 10 years for the first time. It is one of only few long-term surveillance studies in Europe, and allows comparative molecular analyses of HMPV circulating worldwide.

Identification of human metapneumovirus genotypes A and B from clinical specimens by reverse transcription loop-mediated isothermal amplification

Human metapneumovirus (hMPV) has been recognized as an important pathogen for acute respiratory infections in children worldwide and classified into genotypes A and B. Reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay is a rapid diagnostic method for detecting nucleic acids with a single step under isothermal conditions in less than 1h. RT-LAMP targeting the M gene of hMPV was developed for detecting and identifying hMPV genotypes A and B. The detection limit of the genotype-specific hMPV RT-LAMP assay was 10 times greater than that of conventional reverse transcription polymerase chain reaction (RT-PCR). No cross-reactivity was found with respiratory syncytial virus, parainfluenza virus 1-3, adenovirus, human bocavirus, human rhinovirus, influenza virus A and B, human coronaviruses and enteroviruses. One hundred and fifteen clinical specimens were detected for hMPV genotypes A and B with RT-LAMP, RT-PCR and real-time SYBR PCR. Kappa coefficients showed that there was a good agreement among these three methods. Compared with RT-PCR and real-time SYBR PCR, the genotype-specific RT-LAMP showed better specificity, sensitivity and is more convenient to perform with reduced turn-around time.

Genetic variability of human metapneumo- and bocaviruses in children with respiratory tract infections

OBJECTIVES

The genotypic analysis of human metapneumo-(HMPV) and boca-(HBoV) viruses circulating in Greece and their comparison to reference and other clinical strains.

DESIGN

Genetic analysis of representative strains over three consecutive winter seasons of the years 2005-2008.

SETTING

Representative positive specimens for HMPV and HBoV from paediatric patients of healthcare units and hospitals in Southern Greece with influenza-like illness or other respiratory tract infections.

SAMPLE

Seven to ten positive specimens for either HMPV or HBoV from each winter period. In total, 24 specimens positive for HMPV and 26 for HBoV, respectively.

MAIN OUTCOME MEASURES

Sequence diversity of HMPV and HBoV strains by sequencing the complete G and VP1/VP2 genes, respectively.

RESULTS

In total, 24 HMPV strains were found to have a 92-100% nucleotide and a 85.9-100% amino acid identity. Phylogenetic analysis based on the number of amino acid differences, revealed circulation of 4 different subclusters belonging to genetic lineage B2. Similarly, analysis of 26 HBoV strains indicated that 22 clustered within genotype St2, 2 into genotype St1 and the remaining 2 formed a third cluster derived from potential recombination between different St1 genotype strains. St2 HBoV genotype was observed throughout the whole observation period whereas St1 only during the second and the third winter period. Higher levels of heterogeneity were observed between HMPV compared to HBoV strains.

CONCLUSIONS

Phylogenetic analysis revealed circulation of one single lineage (B2) for HMPV viruses and predominance of St2 genotype for HBoV viruses. A possible recombination between St1 genotype strains of HBoV was observed.

Molecular epidemiology of respiratory viruses in virus-induced asthma

Acute respiratory illness (ARI) due to various viruses is not only the most common cause of upper respiratory infection in humans but is also a major cause of morbidity and mortality, leading to diseases such as bronchiolitis and pneumonia. Previous studies have shown that respiratory syncytial virus (RSV), human rhinovirus (HRV), human metapneumovirus (HMPV), human parainfluenza virus (HPIV), and human enterovirus infections may be associated with virus-induced asthma. For example, it has been suggested that HRV infection is detected in the acute exacerbation of asthma and infection is prolonged. Thus it is believed that the main etiological cause of asthma is ARI viruses. Furthermore, the number of asthma patients in most industrial countries has greatly increased, resulting in a morbidity rate of around 10-15% of the population. However, the relationships between viral infections, host immune response, and host factors in the pathophysiology of asthma remain unclear. To gain a better understanding of the epidemiology of virus-induced asthma, it is important to assess both the characteristics of the viruses and the host defense mechanisms. Molecular epidemiology enables us to understand the pathogenesis of microorganisms by identifying specific pathways, molecules, and genes that influence the risk of developing a disease. However, the epidemiology of various respiratory viruses associated with virus-induced asthma is not fully understood. Therefore, in this article, we review molecular epidemiological studies of RSV, HRV, HPIV, and HMPV infection associated with virus-induced asthma.

Prevalence of human metapneumovirus in children with acute lower respiratory infection in Changsha, China

Human metapneumovirus (hMPV) causes acute respiratory infections in children. The prevalence and clinical characteristics of hMPV were determined in nasopharyngeal aspirates of children in Changsha, China. Reverse transcription-polymerase chain reaction (RT-PCR) or PCR was employed to screen for both hMPV and other common respiratory viruses in 1,165 nasopharyngeal aspirate specimens collected from children with lower respiratory tract infections from September 2007 to August 2008. All PCR products were sequenced, and demographic and clinical data were collected from all patients. Seventy-six of 1,165 (6.5%) specimens were positive for hMPV, of which 85.5% (65/76) occurred in the winter and spring seasons. The hMPV coinfection rate was 57.9% (44/76), and human bocavirus was the most common virus detected in conjunction with hMPV. Phylogenetic analysis revealed that 94.7% of the hMPV detected were of subgroup A2, 5.3% were subgroup B2, and none belonged to either the A1 or B1 subgroups. No significant differences were found in terms of the frequency of diagnosis and clinical signs between either the co- and mono-infection groups, or between patients with and without underlying diseases. It was concluded that hMPV is an important viral pathogen in pediatric patients with lower respiratory tract infections in Changsha. Only hMPV genotypes A2 and B2 were co-circulating in this locality; human bocavirus was the most common coinfecting virus, and coinfection did not affect disease severity.

A multicenter outcomes analysis of children with severe viral respiratory infection due to human metapneumovirus

OBJECTIVE

To investigate the impact of human metapneumovirus on morbidity and mortality outcomes in children with severe viral respiratory infection.

DESIGN

Retrospective cohort study.

SETTING

ICU, either PICU or cardiac ICU, at three urban academic tertiary care children's hospitals.

PATIENTS

All patients admitted to an ICU with laboratory-confirmed human metapneumovirus infection between January 2010 and June 2011.

INTERVENTIONS

We captured demographic and clinical data and analyzed associated morbidity and mortality outcomes.

MEASUREMENTS AND MAIN RESULTS

There were 111 patients with laboratory-confirmed human metapneumovirus admitted to an ICU at one of the three participating institutions during the period of study. The median hospital length of stay was 7 days (interquartile range 4-18 days) and median ICU length of stay was 4 days (interquartile range 1-10 days). Ten patients (9%) did not survive to discharge. Predisposing factors associated with increased mortality included female gender (p = 0.002), presence of a chronic medical condition (p = 0.04), and hospital acquisition of human metapneumovirus infection (p = 0.006). Adjusting for female gender, chronic medical conditions, hospital acquisition of infection and severity of illness score, logistic regression analysis demonstrated that female gender, hospital acquisition of infection, and chronic medical conditions each independently increased the odds of mortality (odds ratios 14.8, 10.7, and 12.7, respectively).

CONCLUSIONS

Analysis of our results suggests that there is substantial morbidity and mortality associated with severe viral respiratory infection due to human metapneumovirus in children. Female gender, hospital acquisition of human metapneumovirus infection, and presence of chronic medical conditions each independently increases mortality. The burden of illness from human metapneumovirus on the ICU in terms of resource utilization may be considerable.

Clinical features of different genotypes/genogroups of human metapneumovirus in hospitalized children

BACKGROUND/PURPOSE(S)

To explore the clinical features of different human metapneumovirus (hMPV) genotypes/genogroups in hospitalized children.

METHODS

From January 2005 to April 2010, 3313 children's respiratory specimens sent for the detection of respiratory syncytial virus antigen were also tested for hMPV by real time-polymerase chain reaction. Demographics, clinical presentations, and laboratory findings of patients infected with different genotypes/genogroups of hMPV were compared.

RESULTS

A total of 725 samples were positive for hMPV (positive rate, 23%). The F gene was sequenced for 279 isolates; of these, genotype A was identified in 51% (A1, 6.1%; A2, 45%) and genotype B in 49% (B1, 19%; B2, 30%). Medical records of 152 hospitalized children were reviewed. Co-infection with other pathogens was 25.7% (39/152). Excluding co-pathogens other than respiratory syncytial virus, a total of 124 children were analyzed. The most common symptoms included cough, fever, rhinorrhea, wheezing and respiratory distress with accessory muscle usage. The main diagnosis was bronchiolitis. The most common chest radiographic findings were increased perihilar infiltrates. No significant difference was found in terms of demographics, clinical manifestations, and laboratory findings among the children infected with different serogroups of hMPV.

CONCLUSION

hMPV accounted for a substantial proportion of hospitalized children with lower respiratory tract infection with a high co-infection rate. The A2 subgroup was the most frequently observed, followed by B2. No significant difference was found among patients infected with different genotypes/genogroups of hMPV in terms of clinical manifestations.

Human metapneumovirus-associated hospital admissions over five consecutive epidemic seasons: evidence for alternating circulation of different genotypes

Human metapneumovirus (hMPV) is a pathogen of the respiratory tract with a worldwide distribution. The purpose of this study was to identify hMPV as the cause of acute respiratory diseases in children admitted at Spedali Civili, a public hospital in Brescia, Italy. Eight hundred forty‐six nasopharyngeal aspirate samples negative for the presence of other common respiratory viruses were tested for the presence of hMPV RNA by reverse transcription‐polymerase chain reaction. Of the 846 samples, 79 (9.3%) were positive for hMPV. Polymerase chain reaction products, obtained by amplification of the partial nucleotide sequence of gene F, were sequenced and compared with sequences deposited in GenBank. All four hMPV subtypes were identified, including the proposed subtype A2 sublineages “A” and “B”. In successive epidemic seasons, large outbreaks of hMPV alternated with small outbreaks in a biannual pattern. This local study provides further evidence that hMPV infection should be considered as a reason for hospital admission for acute respiratory disease in children. J. Med. Virol. 84:511–516, 2012. © 2011 Wiley Periodicals, Inc.

Human Metapneumovirus: lessons learned over the first decade

It has been 10 years since human metapneumovirus (HMPV) was identified as a causative agent of respiratory illness in humans. Since then, numerous studies have contributed to a substantial body of knowledge on many aspects of HMPV. This review summarizes our current knowledge on HMPV, HMPV disease pathogenesis, and disease intervention strategies and identifies a number of areas with key questions to be addressed in the future.

Epidemiological and phylogenic study of human metapneumovirus infections during three consecutive outbreaks in Normandy, France

Human metapneumovirus (hMPV) is responsible for respiratory tract disease, particularly in the young and elderly population. An epidemiological and phylogenic study was performed on children admitted to hospital with an acute lower respiratory tract infection (LRI). Data were obtained and analyzed over three consecutive winters, from 2002–2003 to 2004–2005. Each year during the winter period, from November to March, 2,415 nasal swabs were tested by a direct immunofluorescence assay (DFA) for influenza viruses A and B, respiratory syncytial virus, parainfluenza viruses, and adenoviruses. Rhinoviruses, enteroviruses, and coronaviruses OC43 and 229E were detected by RT‐PCR. A RT‐PCR designed for the M gene was performed on negative samples for hMPV detection and phylogenic analyses. For the three consecutive winters, hMPV represented 10%, 22.6%, and 8.8% of virus‐negative samples, respectively. In most cases, clinical symptoms indicated a LRI with a final diagnosis of bronchiolitis. During the winter of 2003–2004, all viral clusters (A1, A2, B1, and B2) that circulated in France shifted progressively from the A group to the B group. This study determined the prevalence of hMPV in Normandy, its clinical impact and permitted the analysis of the molecular evolution during the successive outbreaks. J. Med. Virol. 83:517–524, 2011. © 2011 Wiley‐Liss, Inc.

Prevalence of human metapneumovirus in adults with acute respiratory tract infection in Beijing, China

Objective

To evaluate the prevalence and clinical manifestations of human metapneumovirus (hMPV) in immunocompetent Chinese adults with acute respiratory tract infections (ARTIs).

Methods

A reverse transcription PCR (RT-PCR) assay targeting the P gene was developed in this study and used to detect hMPV in nasal and throat swabs collected from 2936 immunocompetent adult patients with ARTIs in Beijing, China between July 2008 and June 2010.

Results

Among the 2936 patients studied, 49 (1.7%) were positive for hMPV, of whom 14 (28.6%) were positive for hMPV_A2b, 19 (38.8%) for hMPV_B1, and 16 (32.6%) for hMPV_B2. hMPV_A1 was not detected. An average detection rate of 6.6% was observed in the peak months of the two epidemic seasons studied. The hMPV prevalence was higher in the sampled elderly (>65 years, 3.2%) than in middle aged adults (25–65 years; 2.0%) and teenagers (14–25 years; 0.9%). During the study period, hMPV infections showed a biennial rhythm of seasonality, peaking from November to March in 2008/09 and from March to June in 2010.

Conclusion

hMPV infection plays an important role in immunocompetent adults in its epidemic season. The demographic and clinical data presented in this study improves our understanding of the pathogenesis and clinical burden of hMPV infection in adults.