Abstract
Human Metapneumovirus (HMPV) is a respiratory virus similar to many other respiratory viruses, and known to cause seasonal outbreaks of acute respiratory infection (ARI), peaking in late winter to early spring. Symptoms like cough, fever, and nasal congestion are seen, similar to the common cold, and sometimes flu-like symptoms and lower respiratory infection can occur especially in very young children or those with chronic respiratory, medical or immunosuppressive conditions. However, hospitalization rates are low and long-term sequelae not seen. Most children are infected by the age of 5 years, but reinfections can occur anytime throughout life. Supportive and symptomatic care usually leads to recovery in around a week. HMPV is an old known virus and has not shown potential to become a pandemic. Therefore, it should not be looked at with the eye of the COVID experience, and all such misplaced information and fear-spreading on media should be curbed. However, the community especially the high-risk groups should always be reminded and guided of general health, hygienic and lifestyle practices that protect against respiratory infections.
Keywords: HMPV, respiratory infection, flu-like, common-cold, hygiene
Introduction
Human Metapneumovirus (HMPV) also referred to as hMPV, is a respiratory virus similar to other respiratory viruses (like RSV, flu, adenovirus, rhinovirus etc.). It is globally prevalent and generally induces seasonal outbreaks, frequently reaching its peak in late winter to early spring. It causes acute respiratory infection (ARI) with usually mild symptoms like cough, fever, and nasal congestion, similar to the common cold, and has been detected in 4–16% of patients with ARIs.1 It more commonly affects vulnerable groups, mainly young children especially infants, and also the elderly, and those with weakened immune systems and coexisting respiratory or other medical conditions, in whom it may sometimes lead to flu-like symptoms or complications like bronchitis and bronchiolitis (lower respiratory infection) or pneumonia (lung infection)1,2.
Cases of respiratory illnesses associated with HMPV have been reported in various countries across all continents in the past mainly in winter months and early spring. HMPV infection is routinely detected in several children suffering from flu-like symptoms every year, and less than 5% of the HMPV cases require hospitalization. Seroprevalence studies have shown that a high percentage (90–100%) of children have been infected by the time they are 5–10 years old, but re-infection can occur throughout adulthood.3,4
Genetic details
HMPV is not a new virus and is already in circulation globally, including in India, and was found in 2001, in the paramyxovirus family.1,3 It has a genetic relationship to the more known Respiratory Syncytial Virus (RSV). HMPV is a single-stranded, negative-sense RNA virus and encodes 9 proteins. It is classified into two main genetic lineages, A and B, each with two sub-lineages (A1, A2, B1, B2): Lineage differences are mainly in the attachment (G) protein gene, also known as the attachment protein, that plays a role in the initial interaction of the virus with the cell-surface proteoglycans. The F protein, also known as the fusion protein, mediates the fusion of the virus and host-cell membranes. The F protein is highly conserved, immunogenic, and induces protective antibodies. The genetic variability among HMPV strains is relatively low compared to other RNA viruses, but mutations in the G and F proteins can lead to antigenic drift, influencing immune response.
Though co-prevalence of several sub-genotypes or sub-lineages of HMPV has been frequently reported, the thorough relationship between the disease severity and HMPV genotype is yet unclear.3
Clinical Course
Symptoms often are the same as other respiratory infections and can range from mild to severe.1-4 Common symptoms include mild-moderate fever, fatigue, weakness, cough and sore throat, nasal congestion or runny nose, headache/body ache, fatigue, weakness and in some cases breathlessness. In infants, rapid/laboured breathing, wheezing, and flaring of nostrils, as well as increased irritability, reduced activity, and poor feeding may be seen.
Diagnosis of HMPV is confirmed by RT-PCR/RT-qPCR. HMPV is responsible for about 5-10% of hospitalizations of children suffering from acute respiratory tract infections. About 40% of children hospitalized with HMPV infection are found to have underlying high-risk conditions, like asthma and chronic lung disease. The average annual rate of hospitalization was about three times more in children less than 6 months old compared to children 6 months to 5 years old. HMPV infections can lead to asthma exacerbations in small children and both asthma and COPD exacerbations in adults.5 Patients with COPD are also at higher risk for HMPV infection.6
HMPV infections are managed with general home measures, usually requiring no hospitalization. Currently there is no vaccine or antiviral treatment specifically for HMPV, though a vaccine is in phase 2 development.7 Supportive care like hydration, a healthy diet, paracetamol for fever, and other symptomatic medicines are mainstay of management.
In severe cases, HMPV can lead to lower respiratory infection (bronchitis, bronchiolitis, or pneumonia), requiring medical intervention, with oxygen therapy, and hospitalization. One should monitor for signs of respiratory distress especially in infants like bluish lips, lack of feeding, laboured breathing, high-grade fever, severe fatigue, or drop in oxygen saturation on pulse oximetry, and seek immediate medical care if these occur. Early diagnosis and supportive care are essential for managing HMPV in infants.
Addressing Current Concerns
Even though, HMPV is a known virus around for many years, the recent outbreak in China has created a fear and concern due to the COVID Deja vu. However, HMPV infection is not similar to COVID, and has not shown potential to become a pandemic. There has been no significant increase in respiratory illness cases beyond the expected seasonal variations, seen as spikes of respiratory viruses that tend to peak in late winter and spring as is seen generally for all respiratory illnesses.8
According to WHO, based on data published by China, covering the period up to end December 2024, acute respiratory infections have increased during recent weeks and detections of seasonal influenza, rhinovirus, RSV, and HMPV, particularly in northern provinces of China have also increased.9 The observed increase in respiratory pathogen detections is within the range expected for this time of year during the Northern hemisphere winter.9 Chinese authorities report that the health care system is not overwhelmed, there have been no emergency declarations or responses triggered, and no reports of unusual outbreak patterns. WHO continues to monitor respiratory illnesses at global, regional and country levels through collaborative surveillance systems, and provides updates as needed.
While HMPV can spread through respiratory droplets and contaminated surfaces, most cases are mild and resolve within 7-10 days, without any long-term effects. With appropriate precautions, one can effectively manage the condition and control its spread. Ways to prevent HMPV, like any respiratory virus, is through simple hygiene practices like washing hands frequently especially after coming from outside, avoiding touching one’s face with unwashed hands, avoiding close contact with ill individuals, disinfecting frequently touched surfaces, and staying home if unwell. For those with symptoms, measures like covering one’s mouth and nose when sneezing, and avoiding close contact or sharing utensils and personal items with others, can help prevent transmission.10 Children and adults with respiratory conditions should be regular on their medication, and seek medical opinion if any of the symptoms of acute respiratory infection develop.
Conclusion
It is the duty of doctors, healthcare workers and health administrators to act speedily in spreading awareness, removing undue concerns and misplaced fear, and curb spreading of exaggerated or incorrect facts on social media and press. The latter can create stress, and increase healthcare burden as well as give rise to irrational practices and actions. HMPV is a known virus present for more than a quarter century, with cases regularly diagnosed every year in the peak winter/spring season across the globe similar to other respiratory viruses.
Vulnerable sections of the community like young children, elderly, those with respiratory conditions or other medical illnesses, and compromised immunity, should take care by monitoring symptoms, seeking medical attention timely, taking their prescribed medications regularly, and being up to date in their vaccination schedule. The community should be always reminded of general hygienic practices that protect against respiratory infections.
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1Chief Editor, The Indian Practitioner, and Medical Director, Dr Varsha’s Health Solutions, Mumbai. (Corresponding Author– info@drvarsha.com)
2Chief Scientist & Professor, Institute of Genomics and Integrative Biology, Academy of Scientific and Innovative Research, Delhi