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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., (© 2018 Wiley Periodicals, Inc.)

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., (© 2015 Wiley Periodicals, Inc.)

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., (© 2015 Wiley Periodicals, Inc.)

Human metapneumovirus (hMPV) has been identified previously as a cause of respiratory outbreaks in adults, including the elderly. The objective of this study was to document respiratory outbreaks that were caused by hMPV in Ontario, Canada and to identify the various circulating genotypes during April 2009-February 2012. The majority of the outbreaks that were part of this study were in adults (>65 years). Total nucleic acid extraction was done on 123 residual anonymized clinical specimens from 51 different respiratory outbreaks. Specimens were subjected to PCR amplification and Sanger sequencing targeting the F and G genes of hMPV. Phylogenetic analysis was performed to identify genotypes. HMPV accounted for 195 (8.5%) of 2,292 respiratory outbreaks. Genotype A2b was most prevalent, detected in 28 (54.9%) of 51 typed hMPV-positive outbreaks. The genotype A2b2 that was described recently was also identified. In earlier reports, subtype A1 was reported in Canada which was absent in the specimens typed in this study. This shift in genotype may be significant in terms of disease severity, and for any future vaccine considerations. Regular testing for hMPV should be done as part of outbreak investigation., (© 2014 Wiley Periodicals, Inc.)

Human metapneumovirus (hMPV) is considered an important cause of acute respiratory infections. hMPV can cause morbidity in hematopoietic stem cell transplant recipients and recent research has demonstrated that it is an important virus in patients admitted to hospital with respiratory infections and suspected of having pandemic 2009 influenza A (H1N1pdm09) virus. The purpose of this study was to investigate infections caused by hMPV in two groups of patients admitted to hospital: Immunocompromized patients with a potential risk of severe outcomes and immunocompetent patients with severe acute respiratory syndrome. A total of 288 samples were tested: 165 samples were collected from patients with suspected influenza A (H1N1) pdm09 infection during the first pandemic wave in 2009; and 123 samples were collected from patients of a hematopoietic stem cell transplantation program in 2008-2009. Amplification of the hMPV genes was performed by polymerase chain reaction. This was followed by sequencing and phylogenetic analysis. hMPV was detected in 14.2% (41/288) of all samples: 17% (28/165) of immunocompetent patients with suspected H1N1 infection and 10.6% (13/123) among hematopoietic stem cell transplant recipients. hMPV accounted for 12.1% (8/66) of immunocompetent adults patients with severe respiratory infections (median age, 55.9 years). Two hMPV subtypes were identified, A2 (26.9%; 7/26) and B2 (73.1%; 19/26) but no difference was observed between the patient groups in terms of age or immunosuppression level. This study highlights the significance of hMPV in immunocompetent adult patients with severe infections and further investigations are recommended for understanding the impact of this virus., (Copyright © 2012 Wiley Periodicals, Inc.)

Community-acquired pneumonia is a major cause of morbidity and mortality in children worldwide. However, few studies have been conducted on the infection of human metapneumovirus (hMPV) associated with pediatric community-acquired pneumonia in China. Nasopharyngeal aspirates were collected between July 2008 and June 2010 from 1,028 children, aged ≤16.5 years, who were diagnosed with community-acquired pneumonia in Beijing, China. Reverse-transcriptase polymerase chain reaction was used to screen the samples for hMPV and common respiratory viruses. hMPV was detected in 6.3% of the patients with community-acquired pneumonia. This detection rate is the third highest for a respiratory virus in children with community-acquired pneumonia, after that of rhinovirus (30.9%) and respiratory syncytial virus (30.7%). The detection rate of hMPV in 2008/2009 (42/540, 7.8%) was significantly higher than in 2009/2010 (23/488, 4.7%; χ(2)  = 4.065, P = 0.044). The hMPV subtypes A2, B1, and B2 were found to co-circulate, with A2 being most prevalent. These results indicate that hMPV plays a substantial role in pediatric community-acquired pneumonia in China. Overall, these findings provide a better understanding of the epidemiological and clinical features of hMPV infections., (Copyright © 2012 Wiley Periodicals, Inc.)

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., (Copyright © 2012 Wiley Periodicals, Inc.)

Human metapneumovirus (hMPV) causes acute respiratory infections in children and adults. It is classified into two major genetic lineages and each lineage into two sublineages. The purpose of the study was to identify and characterize hMPV in children who presented to the All India Institute of Medical Sciences, New Delhi, India with acute respiratory infection from April 2005 to March 2007. By reverse-transcription polymerase chain reaction, hMPV was detected in 21 (3%) of the 662 nasopharyngeal samples from children with acute respiratory infection and in none of the 120 control children. Seven of the 21 (33%) children infected with hMPV required hospital admission for pneumonia or bronchiolitis. Most hMPV detections were during the winter and spring seasons. The majority (67%, 11/21) of children positive for hMPV were within 24 months of age. Phylogenetic analysis of partial F and N gene and the full G gene sequences showed three sub-lineages of hMPV circulated during the study period, B1, B2, and the novel sub-lineage A2b. The circulation pattern of hMPV genotypes varied by season. Comparison of the F and G genes of eight strains revealed incongruencies in lineage assignments, raising the possibility that recombination had occurred. Sequence analysis also revealed the F gene was relatively conserved whereas the G gene was more variable between the A and B lineages. This study demonstrates that hMPV is an important contributor to acute respiratory infection in children in India, resulting in both outpatient visits and hospitalizations., (Copyright © 2011 Wiley-Liss, Inc.)

Human metapneumovirus (hMPV) has been recognized as an important cause of respiratory tract infections in all age groups and in all geographical area. The role of hMPV in causing respiratory tract infections in Kuwait was not yet investigated. The aim of this study was to determine the prevalence of hMPV infection in Kuwait among patients with respiratory tract infection with respect to other respiratory viruses. During January-December 2009, 460 respiratory samples from 388 patients with respiratory tract infection were collected from different hospitals. They were tested for hMPV RNA by real-time PCR, and for other respiratory viruses by conventional PCR. Out of 388 patients, 110 (28%) were positive for viral respiratory infections; 21 (5.4%) were positive for hMPV, 29 (7.5%) were positive for rhinovirus, 13 (4%) were positive for respiratory syncytial virus, and 10 (3%) were positive for adenovirus. Most (n = 19, 90.5%) of hMPV-positive patients were admitted to the intensive care unit, 76% of them were of age 2 years and below, and 24% of age 59 years and above. All hMPV-positive elderly patients had pneumonia while 50% of hMPV-positive infants had bronchopneumonia. Children with hMPV/rhinovirus co-infection (n = 3, 1%) had recurrent chest infection and frequent intensive care unit admission. The hMPV infection was mostly detected between December and May, and genotype B was more prevalent than genotype A. This is the first study demonstrating the prevalence of hMPV infection in Kuwait, and suggests that hMPV infection is prevalent in infants and elderly patients with lower respiratory tract infection., (Copyright © 2011 Wiley-Liss, Inc.)

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., (Copyright © 2011 Wiley-Liss, Inc.)

The discovery of human Metapneumovirus (hMPV) and human Bocavirus (hBoV) identified the etiological causes of several cases of acute respiratory tract infections in children. This report describes the molecular epidemiology of hMPV and hBoV infections observed following viral surveillance of children hospitalized for acute respiratory tract infections in Milan, Italy. Pharyngeal swabs were collected from 240 children ≤3 years of age (130 males, 110 females; median age, 5.0 months; IQR, 2.0-12.5 months) and tested for respiratory viruses, including hMPV and hBoV, by molecular methods. hMPV-RNA and hBoV-DNA positive samples were characterized molecularly and a phylogenetical analysis was performed. PCR analysis identified 131/240 (54.6%) samples positive for at least one virus. The frequency of hMPV and hBoV infections was similar (8.3% and 12.1%, respectively). Both infections were associated with lower respiratory tract infections: hMPV was present as a single infectious agent in 7.2% of children with bronchiolitis, hBoV was associated with 18.5% of pediatric pneumonias and identified frequently as a single etiological agent. Genetically distinct hMPV and hBoV strains were identified in children examined with respiratory tract infections. Phylogenetic analysis showed an increased prevalence of hMPV genotype A (A2b sublineage) compared to genotype B (80% vs. 20%, respectively) and of the hBoV genotype St2 compared to genotype St1 (71.4% vs. 28.6%, respectively). Interestingly, a shift in hMPV infections resulting from A2 strains has been observed in recent years. In addition, the occurrence of recombination events between two hBoV strains with a breakpoint located in the VP1/VP2 region was identified., (© 2010 Wiley-Liss, Inc.)

Human metapneumovirus is a cause of respiratory tract infections at all ages. Our objectives were to analyze the distribution of the A and B genotypes over 7 years in Dijon and to investigate a possible association between hMPV genotypes and disease severity. During 2002-2009, we genotyped the 100 isolates from children <3 years old with hMPV. Phylogenetic analysis indicated a change in the distribution of hMPV genotype over the years. Severity was then measured by detailed clinical evaluation. The hospitalization rate was greater when genotype B was involved 72.5% versus 53.3% (P = 0.054). Those infected with genotype B tended to have a higher clinical score, as measured by Vicente et al. 2006 (P = 0.07). We showed that, although clinical severity is not clearly associated with hMPV genotype in this study, pathological signs on chest X-ray were observed more often in B subgroup (P < 0.01)., ((c) 2010 Wiley-Liss, Inc.)

Human metapneumovirus (hMPV) has been described as circulating among the Uruguayan population at least since 1998 based on serologic evidence. However, no isolation attempts, molecular detection, or genetic studies have been carried out so far in the country. In the present study, molecular detection of circulating hMPV in children hospitalized with acute respiratory tract infection in Montevideo-Uruguay was carried out by reverse transcription-polymerase chain reaction (RT-PCR) amplification of the hMPV nucleoprotein (N) gene from 217 nasopharyngeal aspirates. Genetic variability analysis of the positive samples was performed by amplification and sequencing of both N and attachment glycoprotein (G) genes. Eighteen of the 217 samples tested positive for hMPV, with tachypnea, chest indrawing, and wheezing being the main clinical symptoms recorded. Phylogenetic analysis of N and G genes showed that Uruguayan samples clustered in genotypes described previously as A2, B1, and B2, with bootstrap values >or=98%. Sublineages A2a and A2b could also be distinguished within the samples that belong to A2. This is the first molecular report on the circulation of hMPV in Uruguay. The pattern of circulation of this virus, analyzed for both N and G genes independently, resembles the complex evolutionary pattern of respiratory syncytial virus (RSV)., ((c) 2010 Wiley-Liss, Inc.)

The human metapneumovirus (hMPV) is a pathogen of the respiratory tract identified first in the Netherlands in 2001 and since then it has been detected worldwide. The purpose of this study was to identify and characterize hMPV in samples collected from children <5 years presenting with acute respiratory disease (ARD) seen at a public hospital in Uberlândia, in Southeastern Brazil. One hundred fourteen nasopharyngeal aspirates (NPAs) samples that were negative for the presence of nine other respiratory viruses were tested by reverse transcription polymerase chain reaction (RT-PCR) for the presence of hMPV RNA. Fourteen out of 114 (12.3%) samples were positive for presence of hMPV RNA. PCR products, obtained by the amplification of partial nucleotide sequence of gene N, were sequenced and compared with sequences deposited in GenBank. Sequences from eight samples were obtained and all four subtypes were identified. Also, the recently proposed sublineages "a" and "b" of subtype A2 were found; mean age was 21 months old; upper respiratory tract infection (URTI) was the most common clinical symptom; the virus was detected in samples collected from March to November, a period that corresponds to late summer to mid-spring in Brazil. This is the first study to describe the circulation of all hMPV subtypes in Minas Gerais state.

Epidemiological and molecular characteristics of human metapneumovirus (hMPV) were compared with human respiratory syncytial virus (hRSV) in infants and young children admitted for acute lower respiratory tract infections in a prospective study during four consecutive years in subtropical Brazil. GeneScan polymerase chain assays (GeneScan RT-PCR) were used to detect hMPV and hRSV in nasopharyngeal aspirates of 1,670 children during January 2003 to December 2006. hMPV and hRSV were detected, respectively, in 191 (11.4%) and in 702 (42%) of the children admitted with acute lower respiratory tract infections at the Sao Paulo University Hospital. Sequencing data of the hMPV F gene revealed that two groups of the virus, each divided into two subgroups, co-circulated during three consecutive years. It was also shown that a clear dominance of genotype B1 occurred during the years 2004 and 2005, followed by genotype A2 during 2006., (Copyright 2009 Wiley-Liss, Inc.)

Impact of recently discovered viruses on epidemiology of acute respiratory tract infections (ARTI) is still unclear. We studied the impact of recently discovered human metapneumovirus (hMPV), human bocavirus (HBoV), and new coronaviruses (HCoV-NL63 and HKU1) on the global epidemiology of ARTI. From October 2006 to April 2007, 237 pediatric patients affected by ARTI were enrolled in our study. Specimens were tested for respiratory viruses by polymerase chain reaction. One hundred twenty-four out of 237 samples (52.3%) were positive for one or more viruses. Picornaviruses were the most prevalent viruses (n = 61, 43.6%), followed by respiratory syncytial virus (n = 34, 24.3%) and Adenovirus (n = 25, 17.9%); hMPV (n = 9, 6.4%) was the fourth most common virus detected. HBoV and HCoV showed a low prevalence (respectively 2.9% and 2.1%). RSV was the prevalent agent of LRTI (38%). Viruses were identified in more than 50% of the studied ARTI, providing useful information on clinical features and epidemiology of specific agents affecting children in cold months. Although routine surveillance of respiratory viruses does not seem cost-effective, continuous monitoring of ARTI etiology could be a useful tool for planning resources for the development of new vaccines and antiviral agents., ((c) 2009 Wiley-Liss, Inc.)

Human metapneumovirus (hMPV) is a significant cause of acute lower respiratory tract infection in all age groups, particularly in children. Two genetic groups and four subgroups of hMPV have been described. They co-circulate during an epidemic in variable proportions. The aims were to characterize the genotypes of hMPV recovered from children hospitalized for acute lower respiratory tract infection and to establish the molecular epidemiology of strains circulating in Santiago of Chile during a 2-year period. The detection of the N gene by reverse-transcription polymerase chain reaction was carried out for screening 545 infants hospitalized for acute lower respiratory tract infection in Santiago during 2003-2004. The genetic typing of hMPV was performed by analyzing the fusion gene sequences. hMPV was detected in 10.2% (56/545 cases). Phylogenetic analysis of F gene sequences from 39 Chilean hMPV strains identified the two groups and four subgroups previously described. Strains clustered into group A were split further into the sub lineages A1, A2, and A3. Most Chilean strains clustered into the proposed novel A3 sub lineage (59%). A3 viruses were present in both years, while A1 and A2 circulated just in 1 year. In conclusion, hMPV is a relevant cause of acute lower respiratory infection in Chilean children and the potential novel cluster of group A emphasize the need for further regional genetic variability studies., ((c) 2008 Wiley-Liss, Inc.)

The presence of human metapneumovirus (hMPV) was analyzed retrospectively by reverse transcriptase-polymerase chain reaction (RT-PCR) in five epidemic seasons, in Stockholm, 2002-2006. The occurrence of hMPV was compared with five common respiratory viruses; respiratory syncytial virus, influenza A virus, influenza B virus, parainfluenza virus and adenovirus. With a detection rate of 2.9% (n = 143/4,989) in nasopharyngeal samples over the whole period, hMPV was the fourth most common respiratory virus after RSV, influenza A and parainfluenza virus. hMPV genotype A dominated over genotype B, out of 91 genotyped virus samples 87 belonged to genotype A and four belonged to genotype B. Approximately 50.3% (n = 72/143) of the hMPV positive patients were <3 years, 49.7% (71/143) were > or =3 years and 38,5% (n = 55/143) were <1 year. The relative frequencies of hMPV infections in the three age groups were 2.8% (72/2,579), 2.9% (71/2,410) and 2.6% (55/2,122), respectively. This age distribution differed from RSV, influenza A, B and parainfluenza virus. hMPV epidemics peaked in March, not coincident with RSV or parainfluenza virus. In successive epidemic seasons, large outbreaks of hMPV alternated with small outbreaks in a regular, biannual pattern. Large hMPV virus epidemics were anticyclical to large RSV epidemics. It is concluded that the epidemiology of hMPV differs markedly from other common respiratory viruses.

Human metapneumovirus was discovered recently respiratory virus implicated in both upper and lower respiratory tract infection. In children, the clinical symptoms of human metapneumovirus are similar to those produced by respiratory syncytial virus, ranging from mild to severe diseases such as bronchiolitis and pneumonia. The aim of the present study was to describe the prevalence of human metapneumovirus and other common respiratory viruses among admitted to hospital infants. From January 2006 to June 2006, 99 nasopharyngeal aspirates were collected from hospitalized children younger than 12 months in order to study respiratory viruses. Human metapneumovirus detection was performed by cell culture and two RT-PCR targeting on polymerase and fusion genes. The latter gene was used for phylogenetic analysis. In 67/99 children (67%) at least one viral pathogen was identified, the viruses detected most frequently were respiratory syncytial virus (35%), human metapneumovirus (25%) and rhinovirus (19%). The results obtained in this study, show that: (1) human metapneumovirus is one of the most important viruses among children less than 12 months; (2) children infected with human metapneumovirus were significantly older than those infected by respiratory syncytial virus; (3) human metapneumovirus was associated more frequently with pneumonia whereas respiratory syncytial virus was only detected in patients with bronchiolitis; (4) there was a clear epidemiological succession pattern with only a small overlap among the viruses detected most frequently; (5) all human metapneumovirus samples were clustered within sublineage A2.

Human metapneumovirus (HMPV) is an important respiratory pathogen, especially among young children. The genetic characteristics of HMPV circulating in Croatia have not been studied so far. The aim of this study was to determine the incidence of HMPV infection in hospitalized children with acute respiratory tract infection (ARTI) in the season 2005/2006 in Croatia, as well as to perform the genotypic analysis of detected HMPV strains. From December 1 to March 31 nasopharyngeal secretions (NPSs) were collected from 402 inpatients up to 5 years of age with ARTI. NPSs were tested by real-time RT-PCR assay targeting the nucleoprotein (N) gene of HMPV. HMPV infection was detected in 33 patients (8.2%). To perform the phylogenetic study, partial nucleotide sequences were obtained for HMPV fusion (F) gene of 30 HMPV positive samples. Phylogenetic analysis showed the circulation of two main genetic lineages (A and B), with B lineages being prevalent. It also showed the existence of two sublineages within the group B (B1 and B2) and three subclusters within lineage A (A1, A2a and A2b). Further molecular analysis revealed point mutations in HMPV strains of sublineage B1.

Human metapneumovirus (hMPV), a virus causing lower respiratory tract infections in children, is classified two major groups or genotypes of hMPV and recently existence of multiple lineages has been suggested. The purpose of this study was to examine the extent of genetic variation and circulation pattern of hMPV in Korea. Between January 2005 and April 2007, nasopharyngeal aspirates were collected from 1,214 children <16 years of age hospitalized with acute respiratory tract infection at Sanggyepaik Hospital. Nasopharyngeal aspirates were tested for common respiratory pathogens using immunofluorescence or multiplex RT-PCR. RT-PCR was used to detect hMPV. The PCR products were purified and subsequently sequenced directly on both strands. hMPV was detected in 8.4% (102/1,214) of nasopharyngeal aspirates from children with acute respiratory tract infection. The 102 hMPV strains detected in this study were classified into two distinct F lineages, 87 strains belonged to genogroup A2 (A2a in 42, A2b in 45) and 15 strains to genogroup B. All hMPV subtypes except A1 co-circulated in Korean population. Although alternating predominance of hMPV subtypes from year to year could not be found, the changing predominance of sublineage A2a and A2b was demonstrated.

The role of the novel respiratory viruses, human metapneumovirus (hMPV), human coronavirus NL63 (HCoV NL63) and human bocavirus (HBoV), in wheezing illness in children has not been well studied, especially in Africa. The aim of this study was to investigate the prevalence of hMPV, HCoV NL63 and HBoV in South African children with acute wheezing. A prospective study of consecutive children presenting with acute wheezing to a pediatric hospital from May 2004 to November 2005 was undertaken. A nasal swab was taken for reverse transcription-polymerase chain reaction (RT-PCR) and PCR for hMPV, HCoV NL63 and HBoV; when positive, the genes were sequenced. Shell vial culture for RSV, influenza A and B viruses, adenovirus and parainfluenza viruses 1, 2, 3 was performed on every 5th sample. Two hundred and forty two nasal swabs were collected from 238 children (median age 12.4 months). A novel respiratory virus was found in 44/242 (18.2%). hMPV, HBoV, and HCoV NL63 was found in 20 (8.3%), 18 (7.4%), and 6 (2.4%) of samples, respectively. Fifteen of 59 (25%) samples were positive for other respiratory viruses. Viral co-infections, occurred in 6/242 (2.5%). Phylogenetic analysis showed co-circulation of hMPV and HCoV NL63 A and B lineages, although only HBoV genotype st2 was found. Viruses are an important cause of wheezing in preschool children; hMPV, HCoV NL63, and HBoV are less common than the usual respiratory pathogens.

Human metapneumovirus (hMPV) is a cause of respiratory illness ranging from wheezing to bronchiolitis and pneumonia in children. A quantitative real-time reverse-transcriptase polymerase chain reaction (RT-PCR) assay was developed for the detection of all four main genetic lineages of hMPV and employed to validate an indirect immunofluorescence (IF) assay to detect hMPV positive specimens. The IF assay detected 24 positives from a screen of 625 randomly selected pediatric respiratory specimens collected (3.8% prevalence). From this cohort of 625 specimens, 229 were also tested by real-time RT-PCR assay. This included the 24 IF positive specimens and 205 randomly selected specimens from both study periods. In addition to confirming all the IF positives, the real-time assay detected an additional six hMPV positive specimens giving rise to a combined prevalence of 4.8%. Phylogenetic analysis showed that hMPV subtypes A2b and B2 to be the most prevalent genotypes circulating in our population and surprisingly no hMPV subgroups A1 or B1 were detected during this study period. Based on this phylogenetic analysis, we propose the existence of sub-clusters of hMPV genotype B2 present in our population which we term subtypes B2a and B2b. The mean log 10 copies/ml of quantitative RT-PCR determinations from these 30 hMPV positive respiratory specimens was 6.35 (range = 4.44-8.15). Statistical analysis of quantitative RT-PCR determinations of viral load from these 30 respiratory specimens suggests that hMPV genotype B specimens have a higher viral load than hMPV genotype A isolates (P < 0.03).

Over two winters in Newcastle upon Tyne, respiratory secretions, negative by immunofluorescence staining for other respiratory viruses, were tested for the presence of human metapneumovirus (HMPV) by RT-PCR. In the second winter, specimens were also tested by immunofluorescence staining with an anti-HMPV polyclonal rabbit antiserum and immunofluorescence positive specimens were inoculated into a line of human bronchiolar cells, 16HBE140. Overall, 55 of 549 (10%) specimens tested were positive for HMPV by RT-PCR. Of 162 specimens tested by both RT/PCR and immunofluorescence staining, 23 were positive by both techniques. Of five specimens positive by RT-PCR alone, only one was confirmed with a second set of primers. Of three specimens positive by immunofluorescence alone, only one was confirmed by virus culture. All four previously recognized sub-genotypes of the virus were identified by both RT-PCR and immunofluorescence staining. Sub-genotype A1 was prevalent in the first winter and B1 prevalent in the second. HMPV replication and virus isolation rates were higher in 16HBE140 cells than in monkey kidney cells and did not require exogenous trypsin. Low passage isolates of both sub-genotypes A2 and B1 replicated slowly reaching peak titers only 12 days after inoculation. In summary, single round RT/PCR and immunofluorescence staining with a polyclonal rabbit antiserum proved of equal sensitivity in the diagnosis of HMPV infection in respiratory secretions both detecting 96% of confirmed positive specimens. 16HBE40 cells provided a significant improvement on monkey kidney cells for the isolation and propagation of the virus.

Human metapneumovirus (hMPV) is a newly identified paramixovirus, associated with respiratory illnesses in all age groups. Two genetic groups of hMPV have been described. The nucleotide sequences of the G and F genes from 11 Argentinean hMPV strains (1998-2003) were determined by RT-PCR and direct sequencing. Phylogenetic analysis showed that hMPV strains clustered into two main genetic lineages, A and B. Strains clustered into A group were split into two sublineages, A1 and A2. All strains belonging to group B clustered with representative strains from sublineage B1. No Argentinean strains belonged to sublineage B2. F sequences showed high percentage identities at nucleotide and amino acid levels. In contrast, G sequences showed high diversity between A and B groups. Most changes observed in the deduced G protein sequence were amino acid substitutions in the extracellular domain, and changes in stop codon usage leading to different lengths in the G proteins. High content of serine and threonine residues were also shown, suggesting that this protein would be highly glycosylated. The potential sites for N- and O-glycosylation seem to have a different conservation pattern between the two main groups. This is the first report on the genetic variability of the G and F protein genes of hMPV strains in South America. Two main genetic groups and at least three subgroups were revealed among Argentinean hMPV strains. The F protein seems to be highly conserved, whereas the G protein showed extensive diversity between groups A and B., (Copyright 2006 Wiley-Liss, Inc.)