Human metapneumovirus infection in young children hospitalized with acute respiratory tract disease: virologic and clinical features

Human metapneumovirus M2-2 protein inhibits RIG-I signaling by preventing TRIM25-mediated RIG-I ubiquitination

Retinoic acid-inducible gene I (RIG-I) is a receptor that senses viral RNA and interacts with mitochondrial antiviral signaling (MAVS) protein, leading to the production of type I interferons and inflammatory cytokines to establish an antiviral state. This signaling axis is initiated by the K63-linked RIG-I ubiquitination, mediated by E3 ubiquitin ligases such as TRIM25. However, many viruses, including several members of the family Paramyxoviridae and human respiratory syncytial virus (HRSV), a member of the family Pneumoviridae, escape the immune system by targeting RIG-I/TRIM25 signaling. In this study, we screened human metapneumovirus (HMPV) open reading frames (ORFs) for their ability to block RIG-I signaling reconstituted in HEK293T cells by transfection with TRIM25 and RIG-I CARD (an N-terminal CARD domain that is constitutively active in RIG-I signaling). HMPV M2-2 was the most potent inhibitor of RIG-I/TRIM25-mediated interferon (IFN)-β activation. M2-2 silencing induced the activation of transcription factors (IRF and NF-kB) downstream of RIG-I signaling in A549 cells. Moreover, M2-2 inhibited RIG-I ubiquitination and CARD-dependent interactions with MAVS. Immunoprecipitation revealed that M2-2 forms a stable complex with RIG-I CARD/TRIM25 via direct interaction with the SPRY domain of TRIM25. Similarly, HRSV NS1 also formed a stable complex with RIG-I CARD/TRIM25 and inhibited RIG-I ubiquitination. Notably, the inhibitory actions of HMPV M2-2 and HRSV NS1 are similar to those of V proteins of several members of the Paramyxoviridae family. In this study, we have identified a novel mechanism of immune escape by HMPV, similar to that of Pneumoviridae and Paramyxoviridae family members.

Role of human metapneumovirus glycoprotein G in modulation of immune responses

Human metapneumovirus (hMPV) is an important pathogen responsible for acute respiratory tract infections in children, the elderly, and immunocompromised patients, with no effective treatment or vaccine currently available. Knowledge of virus- and host-specific mechanisms contributing to the pathogenesis of hMPV infection is still limited. Studies have shown that hMPV surface glycoprotein G is an important virulence factor, by inhibiting innate immune signaling in airway epithelial cells and immune cells. In this study, we investigated the role of G protein in modulating innate and adaptive immune responses in mice infected with a recombinant virus with deletion of G protein (rhMPV-ΔG). Results show that rhMPV-ΔG was strongly attenuated, as it did not induce significant clinical disease, airway obstruction and airway hyperresponsiveness (AHR), compared to infection with a control strain (rhMPV-WT). By analysis of cells in bronchoalveolar fluid and lung tissue, as well as cytokine production, we found that G protein mediates aspects of both innate and adaptive immune responses, including neutrophils, dendritic cells, natural killer cells and B cells. Lung T cells recruited in response to rhMPV-ΔG had a significantly higher activated phenotype compared to those present after rhMPV-WT infection. Despite highly attenuation characterized by low levels of replication in the lung, rhMPV-ΔG was able to induce neutralizing antibodies and to protect mice from a secondary hMPV challenge. However, challenged mice that had received rhMPV-ΔG as primary infection showed some signs of lung disease at the earliest time points, which were less evident in mice that had received the rhMPV-WT strain as primary infection. These results demonstrate some of the mechanisms by which G protein could contribute to airway disease and modulate immune response to hMPV infection.

Role of metapneumoviral glycoproteins in the evasion of the host cell innate immune response

Human metapneumovirus (HMPV), an unsegmented negative-strand RNA virus, is the second most detected respiratory pathogen and one of the leading causes of respiratory illness in infants and immunodeficient individuals. HMPV infection of permissive cells in culture triggers a transient IFN response, which is efficiently suppressed later in infection. We report that two structural glycoproteins of the virus - namely G (Glycoprotein) and SH (Small Hydrophobic) - suppress the type I interferon (IFN) response in cell culture. This is manifested by inhibition of diverse steps of IFN induction and response, such as phosphorylation and nuclear translocation of IFN regulatory factor-3 and -7 (IRF3, IRF7), major transcription factors of the IFN gene. Furthermore, HMPV suppresses the cellular response to IFN by inhibiting the phosphorylation of STAT1 (Signal Transducer and Activator of Transcription 1), required for the induction of IFN-stimulated genes that act as antivirals. Site-directed mutagenesis revealed an important role of critical cysteine (Cys) residues in the Cys-rich carboxy terminal region of the SH protein in IFN suppression, whereas for G, the ectodomain plays a role. These results shed light on the mechanism of IFN suppression by HMPV, and may also offer avenues for new antiviral approaches in the future.

Clinical Features of Human Metapneumovirus-Associated Community-acquired Pneumonia Hospitalizations

BACKGROUND

Human metapneumovirus (HMPV) is a leading cause of respiratory tract infections. Few studies have compared the clinical characteristics and severity of HMPV-associated pneumonia with other pathogens.

METHODS

Active, population-based surveillance was previously conducted for radiographically confirmed, community-acquired pneumonia hospitalizations among children and adults in 8 United States hospitals. Clinical data and specimens for pathogen detection were systematically collected. We described clinical features of all HMPV-associated pneumonia and, after excluding codetections with other pathogen types, we compared features of HMPV-associated pneumonia with other viral, atypical, and bacterial pneumonia and modeled the severity (mild, moderate, and severe) and length of stay using multivariable proportional odds regression.

RESULTS

HMPV was detected in 298/2358 (12.6%) children and 88/2320 (3.8%) adults hospitalized with pneumonia and was commonly codetected with other pathogens (125/298 [42%] children and 21/88 [24%] adults). Fever and cough were the most common presenting symptoms of HMPV-associated pneumonia and were also common symptoms of other pathogens. After excluding codetections in children (n = 1778), compared to HMPV (reference), bacterial pneumonia exhibited increased severity (odds ratio [OR], 3.66; 95% confidence interval [CI], 1.43-9.40), respiratory syncytial virus (RSV; OR, 0.76; 95% CI, .59-.99) and atypical (OR, 0.39; 95% CI, .19-.81) infections exhibited decreased severity, and other viral pneumonia exhibited similar severity (OR, 0.88; 95% CI, .55-1.39). In adults (n = 2145), bacterial (OR, 3.74; 95% CI, 1.87-7.47) and RSV pneumonia (OR, 1.82; 95% CI, 1.32-2.50) were more severe than HMPV (reference), but all other pathogens had similar severity.

CONCLUSIONS

Clinical features did not reliably distinguish HMPV-associated pneumonia from other pathogens. HMPV-associated pneumonia was less severe than bacterial and adult RSV pneumonia, but was otherwise as or more severe than other common pathogens.

The role of viral co-infections in the severity of acute respiratory infections among children infected with respiratory syncytial virus (RSV): A systematic review and meta-analysis

Background

Respiratory syncytial virus (RSV) is the predominant viral cause of childhood pneumonia. Little is known about the role of viral-coinfections in the clinical severity in children infected with RSV.

Methods

We conducted a systematic literature review of publications comparing the clinical severity between RSV mono-infection and RSV co-infection with other viruses in children under five years (<5y). Clinical severity was measured using the following six clinical outcomes: hospitalisation, length of hospital stay, use of supplemental oxygen, intensive care unit (ICU) admission, mechanical ventilation and deaths. We summarised the findings by clinical outcome and conducted random-effect meta-analyses, where applicable, to quantitatively synthesize the association between RSV mono-infection/RSV co-infection and the clinical severity.

Results

Overall, no differences in the clinical severity were found between RSV mono-infection and RSV co-infection with any viruses, except for the RSV-human metapneumovirus (hMPV) co-infection. RSV-hMPV coinfection was found to be associated with a higher risk of ICU admission (odds ratio (OR) = 7.2, 95% confidence interval (CI) = 2.1-25.1; OR after removal of the most influential study was 3.7, 95% CI = 1.1-12.3). We also observed a trend from three studies that RSV-hMPV coinfections were likely to be associated with longer hospital stay.

Conclusion

Our findings suggest that RSV-hMPV coinfections might be associated with increased risk for ICU admission in children <5y compared with RSV mono-infection but such association does not imply causation. Our findings do not support the association between RSV coinfections with other viruses and clinical severity but further large-scale investigations are needed to confirm the findings.

Protocol registration

PROSPERO CRD42019154761.

Pneumoviral Phosphoprotein, a Multidomain Adaptor-Like Protein of Apparent Low Structural Complexity and High Conformational Versatility

Mononegavirales phosphoproteins (P) are essential co-factors of the viral polymerase by serving as a linchpin between the catalytic subunit and the ribonucleoprotein template. They have highly diverged, but their overall architecture is conserved. They are multidomain proteins, which all possess an oligomerization domain that separates N- and C-terminal domains. Large intrinsically disordered regions constitute their hallmark. Here, we exemplify their structural features and interaction potential, based on the Pneumoviridae P proteins. These P proteins are rather small, and their oligomerization domain is the only part with a defined 3D structure, owing to a quaternary arrangement. All other parts are either flexible or form short-lived secondary structure elements that transiently associate with the rest of the protein. Pneumoviridae P proteins interact with several viral and cellular proteins that are essential for viral transcription and replication. The combination of intrinsic disorder and tetrameric organization enables them to structurally adapt to different partners and to act as adaptor-like platforms to bring the latter close in space. Transient structures are stabilized in complex with protein partners. This class of proteins gives an insight into the structural versatility of non-globular intrinsically disordered protein domains.

Human Metapneumovirus Establishes Persistent Infection in Lung Microvascular Endothelial Cells and Primes a Th2-Skewed Immune Response

Human Metapneumovirus (HMPV) is a major cause of lower respiratory tract infections. HMPV infection has been hypothesized to alter dendritic cell (DC) immune response; however, many questions regarding HMPV pathogenesis within the infected lung remain unanswered. Here, we show that HMPV productively infects human lung microvascular endothelial cells (L-HMVECs). The release of infectious virus occurs for up to more than 30 days of culture without producing overt cytopathic effects and medium derived from persistently HMPV-infected L-HMVECs (secretome) induced monocyte-derived DCs to prime naïve CD4 T-cells toward a Th2 phenotype. Moreover, we demonstrated that infected secretomes trigger DCs to up-regulate OX40L expression and OX40L neutralization abolished the pro-Th2 effect that is induced by HMPV-secretome. We clarified secretome from HMPV by size exclusion and ultracentrifugation with the aim to characterize the role of viral particles in the observed pro-Th2 effect. In both cases, the percentage of IL-4-producing cells and expression of OX40L returned at basal levels. Finally, we showed that HMPV, per se, could reproduce the ability of secretome to prime pro-Th2 DCs. These results suggest that HMPV, persistently released by L-HMVECs, might take part in the development of a skewed, pro-Th2 lung microenvironment.

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.

Pneumonia in children admitted to the national referral hospital in Bhutan: A prospective cohort study

OBJECTIVES

The study aim was to describe the etiological profile and clinical characteristics of pneumonia among children hospitalized in Thimphu, Bhutan.

METHODS

This prospective study enrolled children aged 2-59 months admitted to the Jigme Dorji Wangchuck National Referral Hospital with World Health Organization (WHO)-defined clinical pneumonia. Demographic and clinico-radiological data were collected through questionnaires, physical examination, and chest radiography. Blood samples and nasopharyngeal washing were collected for microbiological analysis including culture and molecular methods.

RESULTS

From July 2017 to June 2018, 189 children were enrolled, of which 53.4% were infants. Pneumonia-related admissions were less frequent over the winter. Chest radiographies were obtained in 149 children; endpoints included pneumonia in 39 cases (26.2%), other infiltrates in 31 (20.8%), and were normal in 79 children (53.0%). Non-contaminated bacterial growth was detected in 8/152 (5.3%) blood cultures, with only two cases of Streptococcus pneumoniae. Viral detection in upper respiratory secretions was common, with at least one virus detected in 103/115 (89.6%). The three most-commonly isolated viruses were respiratory syncytial virus (52/115; 45.2%), rhinovirus (42/115; 36.5%), and human parainfluenza virus (19/115; 16.5%). A third of patients with viral infections showed mixed infections. Case fatality rate was 3.2% (6/189).

CONCLUSION

Respiratory viral infections predominated among this cohort of WHO-defined clinical pneumonia cases, whereas bacterial aetiologies were uncommon, highlighting the epidemiologic transition that Bhutan seems to have reached.

Bacterial pneumonia and its associated factors in children from a developing country: A prospective cohort study

Introduction

Pneumonia in children is a common disease yet determining its aetiology remains elusive.

Objectives

To determine the a) aetiology, b) factors associated with bacterial pneumonia and c) association between co-infections (bacteria + virus) and severity of disease, in children admitted with severe pneumonia.

Methods

A prospective cohort study involving children aged 1-month to 5-years admitted with very severe pneumonia, as per the WHO definition, over 2 years. Induced sputum and blood obtained within 24 hrs of admission were examined via PCR, immunofluorescence and culture to detect 17 bacteria/viruses. A designated radiologist read the chest radiographs.

Results

Three hundred patients with a mean (SD) age of 14 (±15) months old were recruited. Significant pathogens were detected in 62% of patients (n = 186). Viruses alone were detected in 23.7% (n = 71) with rhinovirus (31%), human metapneumovirus (HMP) [22.5%] and respiratory syncytial virus (RSV) [16.9%] being the commonest. Bacteria alone was detected in 25% (n = 75) with Haemophilus influenzae (29.3%), Staphylococcus aureus (24%) and Streptococcus pneumoniae (22.7%) being the commonest. Co-infections were seen in 13.3% (n = 40) of patients. Male gender (AdjOR 1.84 [95% CI 1.10, 3.05]) and presence of crepitations (AdjOR 2.27 [95% CI 1.12, 4.60]) were associated with bacterial infection. C-reactive protein (CRP) [p = 0.007]) was significantly higher in patients with co-infections but duration of hospitalization (p = 0.77) and requirement for supplemental respiratory support (p = 0.26) were not associated with co-infection.

Conclusions

Bacteria remain an important cause of very severe pneumonia in developing countries with one in four children admitted isolating bacteria alone. Male gender and presence of crepitations were significantly associated with bacterial aetiology. Co-infection was associated with a higher CRP but no other parameters of severe clinical illness.

Human lung epithelial cells support human metapneumovirus persistence by overcoming apoptosis

Human metapneumovirus (hMPV) has been identified as a major cause of lower respiratory tract infection in children. Epidemiological and molecular evidence has highlighted an association between severe childhood respiratory viral infection and chronic lung diseases, such as asthma and chronic obstructive pulmonary disease. Currently, animal models have demonstrated the ability of hMPV to persist in vivo suggesting a role of the virus in asthma development in children. However, mechanisms involved in hMPV persistence in the respiratory tract are not yet understood. In the present study we monitored hMPV infection in human alveolar epithelial A549 cells in order to understand if the virus is able to persist in these cells upon acute infection. Our data show that hMPV initially induces an apoptotic process in A549 cells through poly (ADP-ribose) polymerase 1 cleavage, caspase-3/7 activation and Wee1 activity. The hMPV-infected cells were then able to overcome the apoptotic pathway and cell cycle arrest in G2/M by expressing B-cell lymphoma 2 and to acquire a reservoir cell phenotype with constant production of infectious virus. These findings provide evidence of the ability of hMPV to persist in alveolar epithelial cells and help in understanding the mechanisms responsible for hMPV persistence in the human respiratory tract.

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.

Human Metapneumovirus and Other Respiratory Viral Infections during Pregnancy and Birth, Nepal

Human metapneumovirus (HMPV) is a respiratory virus that can cause severe lower respiratory tract disease and even death, primarily in young children. The incidence and characteristics of HMPV have not been well described in pregnant women. As part of a trial of maternal influenza immunization in rural southern Nepal, we conducted prospective, longitudinal, home-based active surveillance for febrile respiratory illness during pregnancy through 6 months postpartum. During 2011-2014, HMPV was detected in 55 of 3,693 women (16.4 cases/1,000 person-years). Twenty-five women were infected with HMPV during pregnancy, compared with 98 pregnant women who contracted rhinovirus and 7 who contracted respiratory syncytial virus. Women with HMPV during pregnancy had an increased risk of giving birth to infants who were small for gestational age. An intervention to reduce HMPV febrile respiratory illness in pregnant women may have the potential to decrease risk of adverse birth outcomes in developing countries.

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.

Human Metapneumovirus Attachment Protein Contributes to Neutrophil Recruitment into the Airways of Infected Mice

Human Metapneumovirus (HMPV) is a leading respiratory pathogen that causes lower respiratory tract infections worldwide. Acute HMPV infection induces an exacerbated inflammatory neutrophilic response leading to bronchiolitis and pneumonia. However, the mechanism by which the virus regulates neutrophil infiltration into the airways still remains unexplored. In this work, we used an experimental mouse model of HMPV infection to demonstrate that the attachment (G) protein of HMPV contributes to the recruitment of neutrophils into the airways and modulate the production of neutrophil chemoattractants and Type I IFN responses, specifically IFN-α. These findings provide the first evidence that the HMPV G protein contributes to the in vivo neutrophilic response to HMPV infection and furthers our understanding on virus induced inflammatory responses in the airways.

Influenza and other respiratory viruses: standardizing disease severity in surveillance and clinical trials

INTRODUCTION

Influenza-Like Illness is a leading cause of hospitalization in children. Disease burden due to influenza and other respiratory viral infections is reported on a population level, but clinical scores measuring individual changes in disease severity are urgently needed. Areas covered: We present a composite clinical score allowing individual patient data analyses of disease severity based on systematic literature review and WHO-criteria for uncomplicated and complicated disease. The 22-item ViVI Disease Severity Score showed a normal distribution in a pediatric cohort of 6073 children aged 0-18 years (mean age 3.13; S.D. 3.89; range: 0 to 18.79). Expert commentary: The ViVI Score was correlated with risk of antibiotic use as well as need for hospitalization and intensive care. The ViVI Score was used to track children with influenza, respiratory syncytial virus, human metapneumovirus, human rhinovirus, and adenovirus infections and is fully compliant with regulatory data standards. The ViVI Disease Severity Score mobile application allows physicians to measure disease severity at the point-of care thereby taking clinical trials to the next level.

Human Metapneumovirus Infection in Immunocompromised Patients

Human metapneumovirus (HMPV) is a pathogen associated with respiratory tract infection and is related to avian pneumovirus. Typically, children, the elderly, and those who are immunocompromised are the most susceptible to HMPV infection; however, the virus can infect persons of all ages. In otherwise healthy individuals, HMPV infection is generally self-limiting, but immunocompromised individuals can develop fatal complications. We present a case series of 3 severely immunocompromised patients who were infected with HMPV and describe their clinical course. All 3 patients had acute myeloid leukemia, histories of neutropenic fever, and prolonged hospitalization stays. This case series highlights the severe sequelae observed in individuals infected with HMPV, particularly among those who are immunocompromised.

Systematic review and meta-analysis of respiratory viral coinfections in children

Respiratory infections are a common cause of paediatric morbidity. Clinical outcomes in children hospitalized with single respiratory virus infection are compared with those with two or more viral-viral coinfection. Studies were restricted to those reporting on children aged less than 5 years (PROSPERO CRD#42014009133). Published data to calculate risk ratios (RR) comparing children with single viral infections to coinfection using a random effects model were used. Similar analyses by pathogen pairs and by excluding children with comorbidities were performed. Of 4443 articles reviewed, 19 were included. Overall, no differences in the risk of fever, admission to an intensive care unit (ICU), oxygen use, mechanical ventilation and abnormal radiographs between children with single infection and those with coinfection were found. When analysing only children without comorbidities, the risk of fever (RR = 1.16 to RR = 1.24, 95% confidence intervals (CI) = 1.00-1.55) and ICU admission (RR = 1.08 to RR = 1.31, 95% CI = 0.93-1.83) increased but remained non-significant. Point estimates suggested an increased risk of ICU admission in those coinfected with either respiratory syncytial virus or human metapneumovirus compared with those with single infection but was non-significant. Our findings suggest that coinfection is not associated with increased clinical severity, but further investigations by pathogen pairs are warranted.

Albuterol Use in Children Hospitalized with Human Metapneumovirus Respiratory Infection

Introduction. Human metapneumovirus (HMPV) is a paramyxovirus from the same subfamily as respiratory syncytial virus (RSV) and causes similar acute lower respiratory tract infection. Albuterol in the setting of acute RSV infection is controversial and has not yet been studied in HMPV. We sought to determine the frequency of albuterol use in HMPV infection and the association between albuterol administration and patient outcomes. Methods. We conducted a retrospective cohort study identifying all patients hospitalized in a tertiary care children's hospital with laboratory-confirmed HMPV infection between January 2010 and December 2010. Results. There were 207 patients included in the study; 57% had a chronic medical condition. The median hospital length of stay was 3 days. Only 31% of patients in the study had a documented wheezing history, while 69% of patients received at least one albuterol treatment. There was no difference in length of stay between patients who received albuterol and those who did not. Conclusion. There is a high frequency of albuterol use in children hospitalized with HMPV infection. As with RSV, evidence may not support routine use of bronchodilators in patients with acute HMPV respiratory infection. Research involving additional patient outcomes and illness severity indicators would be useful in future studies.

Immune Response to Human Metapneumovirus Infection: What We Have Learned from the Mouse Model

Human Metapneumovirus (hMPV) is a leading respiratory viral pathogen associated with bronchiolitis, pneumonia, and asthma exacerbation in young children, the elderly and immunocompromised individuals. The development of a potential vaccine against hMPV requires detailed understanding of the host immune system, which plays a significant role in hMPV pathogenesis, susceptibility and vaccine efficacy. As a result, animal models have been developed to better understand the mechanisms by which hMPV causes disease. Several animal models have been evaluated and established so far to study the host immune responses and pathophysiology of hMPV infection. However, inbred laboratory mouse strains have been one of the most used animal species for experimental modeling and therefore used for the studies of immunity and immunopathogenesis to hMPV. This review summarizes the contributions of the mouse model to our understanding of the immune response against hMPV infection.

Human metapneumovirus-associated severe acute respiratory illness hospitalisation in HIV-infected and HIV-uninfected South African children and adults

BACKGROUND

Data on human metapneumovirus (HMPV)-associated severe acute respiratory illness (SARI) are limited in settings with high human immunodeficiency virus (HIV) infection prevalence.

OBJECTIVES

To describe clinical characteristics and seasonality (all sites), and incidence (Soweto only) of HMPV-associated SARI among children and adults.

STUDY DESIGN

Active, prospective, hospital-based, sentinel surveillance for patients hospitalised with SARI was conducted at four sites in South Africa from February 2009-December 2013. Upper respiratory tract samples were tested by multiplex real-time polymerase chain reaction assays for HMPV and other respiratory viruses. Incidence of hospitalisation, stratified by age and HIV-infection status, was calculated for one hospital with population denominators.

RESULTS

HMPV was identified in 4.1% of patients enrolled, including 5.6% (593/10503) in children and 1.7% in adults (≥18 years; 119/6934). The majority of adults (84.0%) had an underlying medical condition, including HIV infection in 87/110 (79.1%). HMPV detection occurred perennially with periods of increased detection, which varied from year to year. The incidence of HMPV-associated hospitalisation in Soweto was highest in infants (653.3 per 100,000 person years; 95% confidence interval (CI) 602.2-707.6). The incidence was higher in HIV-infected persons compared to HIV-uninfected persons in age-groups 5-17 years (RR 6.0; 1.1-20.4), 18-44 years (RR 67.6; 38.0-132.6) and 45-64 years (RR 5.3; 3.4-8.3), while not differing in other age-groups.

CONCLUSIONS

The burden of HMPV-associated SARI hospitalisation among adults occurred predominantly in HIV-infected persons. Among children, infants were at highest risk, with similar burden of hospitalisation in HIV-infected and HIV-uninfected children.

Human metapneumovirus infection activates the TSLP pathway that drives excessive pulmonary inflammation and viral replication in mice

Human metapneumovirus (hMPV) is a leading cause of acute respiratory tract infections in children and the elderly. The mechanism by which this virus triggers an inflammatory response still remains unknown. Here, we evaluated whether the thymic stromal lymphopoietin (TSLP) pathway contributes to lung inflammation upon hMPV infection. We found that hMPV infection promotes TSLP expression both in human airway epithelial cells and in the mouse lung. hMPV infection induced lung infiltration of OX40L(+) CD11b(+) DCs. Mice lacking the TSLP receptor deficient mice (tslpr(-/-) ) showed reduced lung inflammation and hMPV replication. These mice displayed a decreased number of neutrophils as well a reduction in levels of thymus and activation-regulated chemokine/CCL17, IL-5, IL-13, and TNF-α in the airways upon hMPV infection. Furthermore, a higher frequency of CD4(+) and CD8(+) T cells was found in tslpr(-/-) mice compared to WT mice, which could contribute to controlling viral spread. Depletion of neutrophils in WT and tslpr(-/-) mice decreased inflammation and hMPV replication. Remarkably, blockage of TSLP or OX40L with specific Abs reduced lung inflammation and viral replication following hMPV challenge in mice. Altogether, these results suggest that activation of the TSLP pathway is pivotal in the development of pulmonary pathology and pulmonary hMPV replication.

Detection of viral and bacterial pathogens in hospitalized children with acute respiratory illnesses, Chongqing, 2009-2013

Acute respiratory infections (ARIs) cause large disease burden each year. The codetection of viral and bacterial pathogens is quite common; however, the significance for clinical severity remains controversial. We aimed to identify viruses and bacteria in hospitalized children with ARI and the impact of mixed detections.Hospitalized children with ARI aged ≤16 were recruited from 2009 to 2013 at the Children's Hospital of Chongqing Medical University, Chongqing, China. Nasopharyngeal aspirates (NPAs) were collected for detection of common respiratory viruses by reverse transcription polymerase chain reaction (RT-PCR) or PCR. Bacteria were isolated from NPAs by routine culture methods. Detection and codetection frequencies and clinical features and severity were compared.Of the 3181 hospitalized children, 2375 (74.7%) were detected with ≥1 virus and 707 (22.2%) with ≥1 bacteria, 901 (28.3%) with ≥2 viruses, 57 (1.8%) with ≥2 bacteria, and 542 (17.0%) with both virus and bacteria. The most frequently detected were Streptococcus pneumoniae, respiratory syncytial virus, parainfluenza virus, and influenza virus. Clinical characteristics were similar among different pathogen infections for older group (≥6 years old), with some significant difference for the younger. Cases with any codetection were more likely to present with fever; those with ≥2 virus detections had higher prevalence of cough; cases with virus and bacteria codetection were more likely to have cough and sputum. No significant difference in the risk of pneumonia, severe pneumonia, and intensive care unit admission were found for any codetection than monodetection.There was a high codetection rate of common respiratory pathogens among hospitalized pediatric ARI cases, with fever as a significant predictor. Cases with codetection showed no significant difference in severity than those with single pathogens.

Recent advances in the management of acute bronchiolitis

Acute bronchiolitis is characterized by acute wheezing in infants or children and is associated with signs or symptoms of respiratory infection; it is rarely symptomatic in adults and the most common etiologic agent is respiratory syncytial virus (RSV). Usually it does not require investigation, treatment is merely supportive and a conservative approach seems adequate in the majority of children, especially for the youngest ones (<3 months); however, clinical scoring systems have been proposed and admission in hospital should be arranged in case of severe disease or a very young age or important comorbidities. Apnea is a very important aspect of the management of young infants with bronchiolitis. This review focuses on the clinical, radiographic, and pathologic characteristics, as well as the recent advances in management of acute bronchiolitis.

Risk factors for a poor outcome among children admitted with clinically severe pneumonia to a university hospital in Rabat, Morocco

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Pneumonia remains one of the major killers of children in a middle-income country such as Morocco.

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A history of prematurity, a history of fever, leaving in a house with smokers, impaired consciousness, cyanosis, pallor, having ronchi on auscultation and human metapneumovirus infection are all independent risk factors for an adverse outcome.

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A history of asthma is independently associated with a positive outcome.

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Early identification of risk factors for an adverse outcome could improve overall prognosis.

Objectives

Data on prognostic factors among children with severe pneumonia are scarce in middle-income countries. We investigated prognostic factors for an adverse outcome among children admitted to the Hôpital d’Enfants de Rabat, Morocco with World Health Organization-defined clinically severe pneumonia (CSP).

Methods

Children aged 2–59 months admitted to the hospital and fulfilling the CSP definition were recruited into this 13-month prospective study. A poor prognosis was defined as death, a need for intensive care, or a Respiratory Index of Severity in Children (RISC) score ≥3. Multivariate logistic regression was performed to ascertain independent predictive factors for a poor prognosis.

Results

Of the 689 children included in this analysis, 55 (8.0%) required intensive care and 28 died (4.0%). Five hundred and two (72.8%) children were classified as having a good prognosis and 187 (27.2%) as having a poor prognosis. A history of prematurity (odds ratio (OR) 2.50, 95% confidence interval (CI) 1.24–5.04), of fever (OR 2.25, 95% CI 1.32–3.83), living in a house with smokers (OR 1.79, 95% CI 1.18–2.72), impaired consciousness (OR 10.96, 95% CI 2.88–41.73), cyanosis (OR 2.09, 95% CI 1.05–4.15), pallor (OR 2.27, 95% CI 1.34–3.84), having rhonchi on auscultation (OR 2.45, 95% CI 1.58–3.79), and human metapneumovirus infection (OR 2.13, 95% CI 1.13–4.02) were all independent risk factors for an adverse outcome, whereas a history of asthma (OR 0.46, 95% CI 0.25–0.84) was the only independent risk factor for a positive outcome.

Conclusions

The early identification of factors associated with a poor prognosis could improve management strategies and the likelihood of survival of Moroccan children with severe pneumonia.

The epidemiology and aetiology of infections in children admitted with clinical severe pneumonia to a university hospital in Rabat, Morocco

OBJECTIVES

Scarce and limited epidemiological, clinical and microbiological data are available regarding paediatric respiratory tract infections in the Kingdom of Morocco, a middle-income country in northwestern Africa. The results of hospital-based surveillance aiming at describing the aetiology and epidemiology of respiratory distress among children <5 years of age are presented.

METHODS

Children admitted to the Hôpital d'Enfants de Rabat, Morocco, and meeting the World Health Organization clinical criteria for severe pneumonia were recruited over a period of 14 months and were thoroughly investigated to ascertain a definitive diagnosis.

RESULTS

In total, 700 children were recruited for the study. Most frequent clinical diagnoses included wheezing-related conditions (bronchitis/asthma, 46%; bronchiolitis, 15%), while typical bacterial pneumonia was infrequent (only 19% of the cases). Invasive bacterial disease detected by classical microbiology or molecular methods was also uncommon, affecting only 3.5% of the patients, and with an overall low detection of pneumococcal or Haemophilus influenzae type b disease. Conversely, coverage of respiratory viral detection in the nasopharynx was almost universal among cases (92%), with the three most frequent viruses detected being rhinovirus (53%), respiratory syncytial virus (18%) and adenovirus (17%). The overall case fatality rate (CFR) among recruited patients with a known outcome was 4.1% (28/690).

CONCLUSIONS

In Morocco, the epidemiological profile of paediatric acute respiratory infections is markedly shifted towards wheezing-related diseases and thus resembles that of high-income countries. However, the high associated CFRs found in this study call for an improvement in preventive and clinical management strategies.

Comparative epidemiology of human metapneumovirus- and respiratory syncytial virus-associated hospitalizations in Guatemala

Background

Human metapneumovirus (HMPV) is an important cause of acute respiratory infections (ARI), but little is known about how it compares with respiratory syncytial virus (RSV) in Central America.

Objectives

In this study, we describe hospitalized cases of HMPV- and RSV-ARI in Guatemala.

Methods

We conducted surveillance at three hospitals (November 2007–December 2012) and tested nasopharyngeal and oropharyngeal swab specimens for HMPV and RSV using real-time reverse transcription-polymerase chain reaction. We calculated incidence rates, and compared the epidemiology and outcomes of HMPV-positive versus RSV-positive and RSV-HMPV-negative cases.

Results

We enrolled and tested specimens from 6288 ARI cases; 596 (9%) were HMPV-positive and 1485 (24%) were RSV-positive. We observed a seasonal pattern of RSV but not HMPV. The proportion HMPV-positive was low (3%) and RSV-positive high (41%) for age <1 month, whereas these proportions were similar (∼20%) by age 2 years. The annual incidence of hospitalized HMPV-ARI was 102/100 000 children aged <5 years [95% confidence interval (CI): 75–178], 2·6/100 000 persons aged 5–17 years (95%CI: 1·2–5·0), and 2·6/100 000 persons aged ≥18 years (95%CI: 1·5–4·9). Among children aged <5 years, HMPV-positive cases were less severe than HMPV-RSV-negative cases after adjustment for confounders [odds ratio (OR) for intensive care = 0·63, 95% CI 0·47–0·84]; OR for death = 0·46, 95% CI 0·23–0·92).

Conclusions

Human metapneumovirus is a substantial contributor to ARI hospitalization in Guatemala, but HMPV hospitalizations are less frequent than RSV and, in young children, less severe than other etiologies. Preventive interventions should take into account the wide variation in incidence by age and unpredictable timing of incidence peaks.

Prevalence of respiratory viral infection in children hospitalized for acute lower respiratory tract diseases, and association of rhinovirus and influenza virus with asthma exacerbations

PURPOSE

In this study, we aimed to investigate the prevalence of year-round respiratory viral infection in children with lower respiratory tract infection (LRTI) and the relationship between respiratory viral infection and allergen sensitization in exacerbating asthma.

METHODS

We investigated the sources for acute LRTIs in children admitted to our hospital from May 2010 to April 2011. The 6 most common respiratory viruses were isolated from nasopharyngeal aspirate using multiplex reverse transcription-polymerase chain reaction in 309 children; respiratory syncytial virus (RSV), adenovirus (AV), parainfluenza virus (PIV), influenza virus (IFV), human metapneumovirus (hMPV), rhinovirus (RV). Atopic sensitization was defined if more than 1 serum specific Immunoglobulin E level measured using UniCAP (Pharmacia) was over 0.35 IU/mL.

RESULTS

RSV was the most common pathogen of bronchiolitis in hospitalized children through the year. RV or IFV infection was more prevalent in asthma exacerbations compared to other LRTIs. AV and hMPV were more likely to cause pneumonia. RV and IFV were associated with asthma exacerbations in children with atopic sensitization, but not in nonatopic children.

CONCLUSION

RV and IFV are associated with hospitalization for asthma exacerbation in children with atopic sensitization.

Role of human metapneumovirus, influenza A virus and respiratory syncytial virus in causing WHO-defined severe pneumonia in children in a developing country

Objective

The role of respiratory viruses in causing severe, life threatening pneumonia in children in developing countries is not well established. Our study aims to determine the role of human metapneumovirus (HMPV), influenza A virus and respiratory syncytial virus (RSV) in children, aged 6 weeks to 2 years, hospitalized with WHO defined severe pneumonia (tachypnea plus any general danger sign or chest in-drawing) at a public sector hospital in Karachi, Pakistan.

Methods

This study was conducted from November 2010 to September 2011 at Abbassi Shaheed Hospital, a large public tertiary care hospital in Karachi, Pakistan. Children admitted with WHO-defined severe pneumonia were enrolled and throat swabs were obtained to detect respiratory viruses using real time RT-PCR. Chest x-rays of all subjects were obtained and independently interpreted by two radiologists to diagnose radiologic pneumonia.

Results

169 children were enrolled. HMPV was detected in 24 (14.2%), influenza A virus in 9 (5.3%) and RSV in 30 (17.8%) children admitted with severe pneumonia. Of 9 patients with influenza A, 8 tested positive for H1N1. Viral etiology was found in 18% of radiologically confirmed pneumonia. HMPV infections peaked in February and April, influenza A was prevalent in January, June and November and RSV infections were most prevalent from June to September.

Conclusion

HMPV, influenza A and RSV are common causes of WHO-defined severe pneumonia in hospitalized children in Karachi. Knowledge regarding the viral etiology of pediatric pneumonia and individual viral seasonality can help in the recommendation and implementation of appropriate management strategies.

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.

Human metapneumovirus infections are associated with severe morbidity in hospitalized children of all ages

The impact of human metapneumovirus (HMPV) in children aged >5 years and the risk factors associated with disease severity for all ages have not been well characterized. A retrospective cohort study of 238 children aged 0–15 years hospitalized over a 3-year period was performed. Medical records were reviewed for demographic information, clinical parameters and outcomes. Multivariable analyses were performed to identify independent factors associated with worse disease severity assessed by length of hospital stay (LOS), need for ICU care, respiratory support, and a disease severity score. Pulmonary diseases were associated with all outcomes of care, while congenital heart disease (CHD) and neuromuscular disorders were associated with longer LOS, and CHD and trisomy 21 were associated with worse severity scores independent of other covariables. Fever, retractions, use of steroids and albuterol were also associated with enhanced disease severity. Understanding the determinants of HMPV disease in children may help design targeted preventive strategies.

Critical role of MDA5 in the interferon response induced by human metapneumovirus infection in dendritic cells and in vivo

Human metapneumovirus (hMPV) is a respiratory paramyxovirus of global clinical relevance. Despite the substantial knowledge generated during the last 10 years about hMPV infection, information regarding the activation of the immune response against this virus remains largely unknown. In this study, we demonstrated that the helicase melanoma differentiation-associated gene 5 (MDA5) is essential to induce the interferon response after hMPV infection in human and mouse dendritic cells as well as in an experimental mouse model of infection. Our findings in vitro and in vivo showed that MDA5 is required for the expression and activation of interferon (IFN) regulatory factors (IRFs). hMPV infection induces activation of IRF-3, and it regulates the expression of IRF-7. However, both IRF-3 and IRF-7 are critical for the production of type I and type III IFNs. In addition, our in vivo studies in hMPV-infected mice indicated that MDA5 alters viral clearance, enhances disease severity and pulmonary inflammation, and regulates the production of cytokines and chemokines in response to hMPV. These findings are relevant for a better understanding of the pathogenesis of hMPV infection.

Human metapneumovirus associated with community-acquired pneumonia in children in Beijing, China

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%; χ² = 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. J. Med. Virol. 85:138–143, 2012. © 2012 Wiley Periodicals, Inc.

Human metapneumovirus (hMPV) in acute respiratory infection: a clinic-based study in Egypt

OBJECTIVE

To estimate the prevalence of Human metapneumovirus (hPMV), its epidemiological and clinical features in infants and children with respiratory infections, attending outpatients' clinic of Mansoura University Children Hospital (MUCH).

METHODS

After taking history, clinical examination and appropriate investigations, nasopharyngeal aspirates were collected from 600 infants and children with symptoms and signs of respiratory infections. Samples were examined by RT-PCR for hMPV.

RESULTS

The overall prevalence of hMPV infection among studied patients was 8% (95% = 6.1-10.4). The rate was significantly higher among children aged 2-24 mo compared to other age groups (11.9% vs. 3.7% and 4.0% for 2-24, 25-60, 61-108 mo respectively). Also it was significantly higher among females than males (12.6% vs. 6.6%). Cough, wheezing, rhinorrhea, fever and chest wall retraction were the most frequent presentations (81.2%, 68.8%, 66.7%, 64.6% and 56.3%; respectively). Antibiotics, bronchodilators and oxygen administration were the most common treatments offered (60.4%, 31.2% and 27.1%; respectively).

CONCLUSIONS

hMPV is an emerging cause of acute respiratory infection in Mansoura University Children Hospital (MUCH), and may have a significant clinical impact on infants and children and thus, must be considered in etiological diagnosis.

Evaluation of viral co-infections in hospitalized and non-hospitalized children with respiratory infections using microarrays

The impact of viral co‐infections and recently discovered viruses on the epidemiology of respiratory infections in children is still unclear. To simultaneously detect viruses that are involved in the aetiology of respiratory infections, we used a DNA/RNA microarray assay that identifies 17 different viruses or viral subtypes. Rhinopharyngeal washes were taken from 611 children (aged 1 month to 14 years) who presented in the emergency department with respiratory infections from June 2010 to June 2011 and were treated as outpatients (299, 48.9%) or hospitalized (312, 51.1%). Lower respiratory tract infection was diagnosed more often in hospitalized children (68% versus 36%, p 0.001). Of 397 children in which microarrays detected viral infection (70.1%), a single virus was found in 228 (57.4%) and two or more viruses in 169 (42.5%). The most prevalent viruses among children with positive samples were respiratory syncytial virus (RSV) in 225 (56.6%), parainfluenza virus (PIV) in 118 (29.7%), rhinovirus (RV) in 73 (18.4%), followed by influenza in 56 (14.1%), adenoviruses in 31 (7.8%), bocavirus in 25 (6.3%), human metapneumovirus in 15 (3.7%) and enteroviruses in 12 (3%). Most common viral co‐infections were RSVA–RSVB in 46 children (27.2%), RSV–Influenza in 20 (11.8%), RSV–RV in 18 (10.6%) and PIV–RV in 13 (7.7%). Multiple logistic regression analysis revealed that viral co‐infections were associated with increased probability for hospitalization (OR 1.52, 95% CI 1.01–2.29, p 0.04), and previous pneumococcal vaccination was associated with decreased probability for hospitalization (OR 0.52, 95% CI 0.33–0.81, p 0.004). We conclude that viral co‐infections are involved in a significant proportion of children with an acute respiratory infection and may increase the severity of clinical presentation and the risk for hospitalization.

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.

Viral load and acute otitis media development after human metapneumovirus upper respiratory tract infection

The role of human metapneumovirus (hMPV) in acute otitis media complicating upper respiratory tract infection (URI) was studied. Nasopharyngeal specimens from 700 URI episodes in 200 children were evaluated; 47 (7%) were positive for hMPV, 25 (3.6%) with hMPV as the only virus. Overall, 24% of URI episodes with hMPV only were complicated by acute otitis media, which was the lowest rate compared with other respiratory viruses. hMPV viral load was significantly higher in children with fever, but there was no difference in viral load in children with hMPV-positive URI with or without acute otitis media complication.

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.

Epidemiology of human metapneumovirus in a pediatric long-term care facility

BACKGROUND

Viral respiratory pathogens cause outbreaks in pediatric long-term care facilities (LTCFs), but few studies have used viral diagnostic testing to identify the causative pathogens. We describe the use of such testing during a prolonged period of respiratory illness and elucidate the epidemiology of human metapneumovirus (hMPV) at our LTCF.

DESIGN

Retrospective study of influenza-like illness (ILI).

SETTING

A 136-bed pediatric LTCF from January 1 through April 30, 2010.

METHODS

The ILI case definition included fever, cough, change in oropharyngeal secretions, increase in oxygen requirement, and/or wheezing.

RESULTS

During the study period, 69 episodes of ILI occurred in 61 (41%) of 150 residents. A viral pathogen was detected in 27 (39%) of the episodes, including respiratory syncytial virus (RSV) (n = 3), influenza A virus (not typed; n = 2), parainfluenza virus (n =2), adenovirus (n = 1), and hMPV (n = 19). Twenty-seven of the residents with ILI (44%) required transfer to acute care hospitals (mean length of hospitalization, 12 days; range, 3-47 days). Residents with tracheostomies were more likely to have ILI (adjusted odds ratio [OR], 3.99 [95% confidence interval {CI}, 1.87-8.53]; P = .0004). The mortality rate for residents with ILI was 1.6%. Residents with hMPV were younger (P = .03), more likely to be transferred to an acute care facility (OR, 3.73 [95% CI, 1.17-11.95]; P = .02), and less likely to have a tracheostomy (adjusted OR, 0.19 [95% CI, 0.047-0.757]; P = .02 ).

DISCUSSION

Diverse pathogens, most notably hMPV, caused ILI in our pediatric LTCF during a prolonged period of time. Viral testing was helpful in characterizing the epidemiology of ILI in this population.

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.

Evolutionary dynamics analysis of human metapneumovirus subtype A2: genetic evidence for its dominant epidemic

Human metapneumovirus (hMPV) is a respiratory viral pathogen in children worldwide. hMPV is divided into four subtypes: hMPV_A1, hMPV_A2, hMPV_B1, and hMPV_B2. hMPV_A2 can be further divided into hMPV_A2a and A2b based on phylogenetic analysis. The typical prevalence pattern of hMPV involves a shift of the predominant subtype within one or two years. However, hMPV_A2, in particular hMPV_A2b, has circulated worldwide with a several years long term high epidemic. To study this distinct epidemic behavior of hMPV_A2, we analyzed 294 sequences of partial G genes of the virus from different countries. Molecular evolutionary data indicates that hMPV_A2 evolved toward heterogeneity faster than the other subtypes. Specifically, a Bayesian skyline plot analysis revealed that hMPV_A2 has undergone a generally upward fluctuation since 1997, whereas the other subtypes experienced only one upward fluctuation. Although hMPV_A2 showed a lower value of mean dN/dS than the other subtypes, it had the largest number of positive selection sites. Meanwhile, various styles of mutation were observed in the mutation hotspots of hMPV_A2b. Bayesian phylogeography analysis also revealed two fusions of diffusion routes of hMPV_A2b in India (June 2006) and Beijing, China (June 2008). Sequences of hMPV_A2b retrieved from GenBank boosted simultaneously with the two fusions respectively, indicating that fusion of genetic transmission routes from different regions improved survival of hMPV_A2. Epidemic and evolutionary dynamics of hMPV_A2b were similar to those of hMPV_A2. Overall, our findings provide important molecular insights into hMPV epidemics and viral variation, and explain the occurrence of an atypical epidemic of hMPV_A2, particularly hMPV_A2b.

Acute Pulmonary Infections

Acute lower respiratory infection is a common cause of morbidity in infants and children, and at times, requires intensive care and mechanical ventilation. Viral bronchiolitis and bacterial pneumonia account for the majority of lower respiratory tract infections that lead to respiratory insufficiency and pediatric intensive care admission. Twenty-seven percent of children who require mechanical ventilation for at least 24 h in pediatric intensive care units are diagnosed with bronchiolitis and 16% have the diagnosis of pneumonia. The median length of time intubated for an acute pulmonary infection leading to respiratory failure is approximately 7 days.

Human metapneumovirus strains circulating in Latin America

The human metapneumovirus (HMPV) is responsible for acute respiratory tract infections in young children, elderly patients, and immunocompromised hosts. In this study, we genetically analyzed the circulating HMPV in Central and South America from July 2008 to June 2009 and characterized the strains present in this region. Samples were collected during an international collaborative influenza like illness surveillance study and then sequenced with specific primers for the HMPV G gene. Our results show that two distinct clusters of HMPV circulated in Central and South America, subtypes A2 and B2 being the predominant strains.