Human Metapneumovirus
Human metapneumovirus (hMPV) is an important respiratory pathogen that has gained increasing recognition in clinical practice over the past two decades. Despite being discovered relatively recently in 2001, it has emerged as a significant cause of respiratory tract infections across all age groups.
What is Human Metapneumovirus?
Human metapneumovirus (HMPV or hMPV) is a negative-sense single-stranded RNA virus of the family Pneumoviridae and is closely related to the Avian metapneumovirus (AMPV) subgroup C. It is a common cause of both upper and lower respiratory tract infections, with clinical manifestations ranging from mild cold-like symptoms to severe bronchiolitis and pneumonia.
hMPV is ubiquitous worldwide, with peak activity typically occurring in late winter and spring. The virus predominantly affects young children, the elderly, and immunocompromised individuals, but it can also infect healthy adults.
Epidemiology and Transmission
hMPV is primarily spread via respiratory droplets or direct contact with contaminated surfaces. It has been detected in up to 10% of respiratory infections during seasonal outbreaks, and co-infections with other viruses, such as RSV or influenza, are common.
In pediatric populations, hMPV is the second leading cause of bronchiolitis after RSV. Adults, particularly those with chronic lung diseases or immunosuppression, are also at risk of severe disease. Healthcare-associated outbreaks of hMPV have been reported, emphasizing its role in nosocomial infections.
Recent Outbreak
The ongoing HMPV outbreak in East Asia (2024-present) began in Beijing, China, in December 2024, when the Chinese Center for Disease Control and Prevention reported a significant rise in human metapneumovirus (HMPV) infections during the week of December 16-22. This increase brought the virus into public focus, highlighting its potential to cause widespread respiratory illness.
In India, the first confirmed HMPV cases have been reported, marking an important milestone in the outbreak’s spread. As of Tuesday, the Indian Council of Medical Research (ICMR) documented seven cases across the country:
Nagpur: Two cases reported on Tuesday.
Bengaluru: Two cases.
Ahmedabad, Chennai, and Salem: One case each reported on Monday.
The patients include a three-month-old girl who tested positive for HMPV and an eight-month-old boy co-infected with HMPV and respiratory syncytial virus (RSV). These cases underscore the virus’s ability to infect individuals across all age groups, with young children, older adults, and immunocompromised individuals being most at risk for severe illness.
Clinically, HMPV can lead to upper and lower respiratory diseases with symptoms such as cough, fever, nasal congestion, and shortness of breath. Healthcare providers should remain vigilant, particularly for vulnerable populations, as the outbreak evolves.
Clinical Presentation
The clinical manifestations of hMPV can vary widely based on the patient’s age and underlying health:
Children: Symptoms often mimic RSV, including rhinorrhea, cough, fever, wheezing, and respiratory distress. Severe cases may require hospitalization for bronchiolitis or pneumonia.
Adults: Typically present with upper respiratory symptoms, but in older adults and those with comorbidities, hMPV can cause exacerbations of chronic obstructive pulmonary disease (COPD), asthma, or pneumonia.
Immunocompromised Patients: Severe and prolonged illness is common, with increased risk of complications such as secondary bacterial infections.
Diagnosis
Accurate diagnosis of hMPV requires laboratory confirmation, as its clinical features overlap significantly with other respiratory viruses. Diagnostic methods include:
Reverse Transcription Polymerase Chain Reaction (RT-PCR): The gold standard for hMPV detection, offering high sensitivity and specificity.
Antigen Detection: Rapid tests are available but are generally less sensitive than RT-PCR.
Serology: Retrospective diagnosis through paired serological testing, though rarely used in clinical practice.
Management and Treatment
There is no specific antiviral therapy for hMPV, and management is primarily supportive. Key aspects include:
Symptomatic Relief: Antipyretics for fever, adequate hydration, and oxygen therapy for hypoxia.
Hospitalization: Reserved for patients with severe respiratory distress, significant hypoxemia, or complications such as secondary bacterial infections.
Bronchodilators and Corticosteroids: Their role remains controversial and is typically reserved for patients with underlying asthma or COPD exacerbations.
Prevention
Currently, there are no approved vaccines or specific prophylactic agents for hMPV. Preventive measures focus on:
Infection Control: Hand hygiene, respiratory etiquette, and disinfection of surfaces.
Protecting Vulnerable Populations: Avoiding contact with symptomatic individuals and using isolation protocols in healthcare settings to prevent nosocomial spread.
