Review of the Hazardous Respiratory Tract Illnesses Known as Human Metapneumovirus (hMPV)

Abstract

Human metapneumovirus (hMPV), a virus discovered in 2001, mainly causes upper and lower respiratory tract infections in children, but can also affect the elderly as well as those with weakened immune systems. hMPV is the leading cause of severe lower respiratory tract infections in 5-10% of hospitalized children. The young children that were infected with hMPV experienced serious bronchiolitis and pneumonia, and the signs and symptoms. are the same as those seen in human respiratory syncytial virus, or HPV, infection. First hMPV infection usually occurs in early childhood, but re-infections are common at all ages. Due to the slow growth of the virus in cell culture, molecular diagnostic tools (e.g., RT-PCR) are the diagnostic of choice for hMPV detection. Many vaccine candidates are effective in preventing clinical disease but none are available to purchase. Our understanding of hMPV has developed rapidly in the last several years, and in this review, we will focus on current knowledge of the molecular biology and epidemiology of hMPV. We will also review the current therapeutic approaches and tactics used to combat hMPV infection, with the hope of proposing some ideas for designing effective vaccines against hMPV.

Keywords

Introduction

The virus known as human metapneumovirus (hMPV) was initially identified in the Netherlands in 2001 after being isolated from a pediatric child who had signs that resemble those of an infection with hRSV¹.

Since then, 4–16% of ARI patients have been found to have hMPV. In the same region, the prevalence of hMPV may change from year to year. Although hMPV mainly affects children, it can also infect adults and others with weakened immune systems².

The sickness brought on by a hMPV infection might manifest clinically as anything from a minor upper respiratory tract infection to potentially fatal acute pneumonia and bronchiolitis.

Children's respiratory issues can be caused by a variety of etiological agents³. Upper respiratory tract infections have substantial societal costs in the form of missed work, missed school days, and additional medical expenses, despite the fact that they are typically less serious⁴. Determining the etiological agents of these infections is crucial because of this. We have established the significance of recognized viral pathogens such as the coronavirus, rhinovirus, influenza virus, parainfluenza virus, and human respiratory syncytial virus (hRSV) through decades of research and epidemiological studies⁵. A significant percentage of respiratory tract infections, nevertheless, are still unattributable to any known pathogen in spite of these investigations⁶.

EPIDEMIOLOGY

In 2001, scientists first identified human metapneumovirus in the Netherlands. It caused symptoms in children, but serological studies showed that this virus had been circulating in the Netherlands since 1958⁷. HMPV infections can happen throughout the year, but they peak in late winter and early spring in the northern hemisphere. Infections occur globally across all continents. The four subgroups A1, A2, B1, and B2 do not appear to cause different levels of severity in infections compared to one another⁸. There is also no dominance of one strain over the others.

EVALUATION

The identification of HMPV usually depends on a clinical diagnosis and often does not require confirmatory testing. However, there are laboratory tests available for use. Typically, confirmation of HMPV infection is done through reverse transcriptase-polymerase chain reaction (RT-PCR) using nasopharyngeal swabs⁹. Radiographic results from a chest X-ray are usually nonspecific, unless HMPV leads to bronchiolitis or pneumonia. Findings may include lobar infiltrates, parabronchial cuffing, hyperinflation, or widespread perihilar infiltrates. It is important to assess vital signs and carry out a thorough physical exam to check for signs of respiratory distress and hydration status. This evaluation will help guide necessary supportive care¹⁰.

TRANSMISSION

Transmission of HMPV from an infected individual to others can occur through personal contact, droplets from coughing and sneezing, or touching a surface with HMPV on it and then touching your mouth, nose, or eyes before washing your hands¹¹.

PATHOGENESIS

HMPV interferes with the host’s innate immune system using specific mechanisms. The virus antagonizes cellular responses by regulating pattern recognition receptors, such as toll-like receptors, retinoic acid-inducible gene-like receptors, and other signalling molecules. HMPV infections may lead to a minimal and late immune response and delayed cytotoxic T-lymphocyte activity with impaired virus clearance during primary infection. Infection interferes with dendritic cell activity and reduces antigen-specific T-cell activation. Thus, virus clearance remains incomplete, and there is an increased chance of re-infection. The proliferation of antigen-specific CD4+ T cells is restricted, and the production of long-term immunity is impaired. HMPV infection induces toll-like receptor-dependent cellular signalling¹².

DIAGNOSIS

Laboratories identify human metapneumovirus using antigen detection and molecular detection (polymerase chain reaction, PCR)¹³.

CONCLUSION

Human metapneumovirus is a relatively recently described virus1 and hMPV appears to be as dangerous a pathogen as hRSV in terms of morbidity and mortality. As an important respiratory pathogen, understanding hMPV pathogenesis and molecular constraints for severe disease is essential for the treatment of infection and for the development of an effective vaccine against hMPV. Recent studies using animal models for hMPV infection and reverse genetics platforms have shed some light on hMPV pathogenesis and have allowed us to evaluate live vaccine candidates. Now we need to initiate the clinical trials to evaluate the different modalities of treatment available for hMPV infection.

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