Written By: Mrs. Mayuri Mathur

Published On: 08 Jan, 2025 1:32 PM | Updated On: 09 Jan, 2025 11:54 AM

Human Metapneumovirus (HMPV): What Everyone Should Know

What is HMPV and Why Is It Important?

Respiratory disorders remain a leading cause of morbidity and mortality among children worldwide, affecting populations in both low and high income countries. Among the various pathogens implicated, human metapneumovirus (hMPV) plays a significant role in respiratory infections among all age groups. ^[1]

HMPV, first identified in 2001 in the Netherlands from respiratory samples of infants and young children with unexplained respiratory illnesses, is an enveloped RNA virus belonging to the Paramyxoviridae family, Pneumovirinae subfamily. Closely related to respiratory syncytial virus (RSV) and parainfluenza viruses, hMPV primarily circulates during winter, causing respiratory illnesses in young infants, often presented with wheezing and bronchiolitis. Despite infection, hMPV induces incomplete immunity, leading to the chances of reinfections across all age groups. ^[2,3]

Human metapneumovirus is important due to its significant contribution to the global burden of respiratory illnesses, particularly in vulnerable populations such as young children, the elderly, and immunocompromised individuals ^[4]. The following reasons highlight its clinical impact:

1. Global Prevalence: hMPV is a ubiquitous respiratory pathogen, with outbreaks reported worldwide, particularly during the winter months. ^[4]
2. Marked Clinical Manifestations: It is a leading cause of bronchiolitis and pneumonia in young children, conditions that can result in hospitalization. ^[5,6]
3. Incomplete Immunity and Reinfection: Unlike some viral infections, hMPV does not confer long-lasting immunity, leading to the potential for reinfections throughout life, which can burden healthcare systems. ^[7]
4. Closely Resembles RSV: hMPV often mimics respiratory syncytial virus (RSV) in clinical presentation, complicating accurate diagnosis and management. ^[6]
5. Impact on Healthcare: hMPV-related hospitalizations increase healthcare utilization and costs, particularly in pediatric and intensive care units. ^[1,2]
6. Lack of Specific Treatment: The absence of specific antiviral therapies or vaccines for hMPV underscores the need for continued research into preventive and therapeutic strategies. ^[2]

Understanding hMPV's role in respiratory illness is crucial for improving clinical outcomes, guiding public health interventions, and informing vaccine development efforts.

How Does HMPV Spread?

The infection is highly transmissible, with multiple modes of spread, such as^{: [8]}

1. Respiratory Droplets: Transmission occurs via respiratory droplets released into the air when an infected individual coughs, sneezes, or talks.
2. Direct Contact: Infection can result from direct physical contact with an infected person, particularly when such hands come into contact with the face, eyes, or mouth.
3. Contaminated Surface: hMPV can persist on surfaces, facilitating indirect transmission when individuals touch contaminated objects, such as doorknobs, mobile devices, or toys, and subsequently touch their faces.
4. Airborne Particles: Small aerosolized particles containing the virus may remain suspended in the air, particularly in crowded or poorly ventilated environments, further contributing to its spread.

These diverse transmission pathways highlight the need for effective preventive measures, including good hand hygiene, respiratory etiquette, and proper ventilation in shared spaces.

High-Risk Populations for hMPV Infection ^[9]

1. Young Children: Infants and toddlers are particularly susceptible to severe respiratory illnesses, including bronchiolitis and pneumonia, due to their underdeveloped immune systems.
2. Older Adults: Individuals aged 65 years and above, especially those with chronic conditions such as asthma, chronic obstructive pulmonary disease (COPD), or heart disease, are at increased risk of severe complications.
3. Pregnant Women: hMPV infection during pregnancy can pose significant health risks, potentially leading to respiratory complications that may adversely affect both maternal and fetal outcomes.
4. Immunocompromised Individuals: Patients with compromised immune systems, whether due to underlying medical conditions, immunosuppressive therapies, or treatments like chemotherapy, are at heightened risk for severe and prolonged illness.

HMPV vs. Flu and Common Cold ^[10,11]

Diagnostic Techniques for hMPV

hMPV PCR Test:

The polymerase chain reaction (PCR) test is a highly sensitive and specific diagnostic tool that detects the genetic material of hMPV. It is considered the gold standard for accurately diagnosing hMPV infections. ^[10]

Rapid Antigen Tests

Rapid antigen tests offer quicker results, making them useful for point-of-care diagnostics. However, they are less sensitive compared to PCR. ^[10]

Bronchoscopy

Bronchoscopy is employed to directly visualize and assess changes in the airways and lungs, particularly in severe or complicated cases of respiratory illness, aiding in comprehensive evaluation and management. ^[10]

Treatment:

Currently, the management of hMPV infection is predominantly supportive, focusing on alleviating symptoms and preventing complications. However, emerging evidence suggests the potential utility of targeted therapeutic approaches, including ribavirin, immunoglobulins, fusion inhibitors, and small interfering RNA (siRNA) molecules, for the treatment and control of hMPV infections. These options, while promising, require further investigation to establish their efficacy and safety in clinical settings. ^[10]

Preventing hMPV Infection: Practical Measures

Since no vaccine is currently available for human metapneumovirus (hMPV), implementing effective preventive strategies is essential to minimize the risk of infection. While hMPV can cause significant respiratory illness, it is important to remain calm, as most infections are mild and manageable. ^[10]

1. Practice Proper Hygiene

• Wash hands thoroughly with soap and water for at least 20 seconds.
• Use alcohol-based hand sanitizers if soap and water are unavailable.

2. Limit Close Contact

• Maintain distance from individuals displaying symptoms of respiratory illness.
• Avoid crowded spaces, particularly during outbreaks.

3. Regularly Disinfect Surfaces

• Clean frequently touched surfaces such as doorknobs, phones, and countertops with disinfectants.

4. Use Protective Measures

• Wear masks during outbreaks or flu season to reduce exposure to respiratory droplets.

5. Isolate When Unwell

• If you experience symptoms of respiratory illness, stay at home to prevent spreading the virus to others.

Conclusion

While hMPV is a notable respiratory pathogen, most cases are mild and resolve with supportive care. Awareness of preventive measures and early detection can significantly reduce the risk of infection and transmission. There is no cause for alarm—practicing simple, effective hygiene and protective habits is sufficient to safeguard against hMPV. ^[8.9,10]

References:

1. Jesse ST, Ludlow M, Osterhaus ADME. Zoonotic Origins of Human Metapneumovirus: A Journey from Birds to Humans. Viruses. 2022;14(4):677. Published 2022 Mar 25. 
2. Soto JA, Gálvez NMS, Benavente FM, et al. Human metapneumovirus: mechanisms and molecular targets used by the virus to avoid the immune system. Frontiers in Immunology. 2018;9. doi:10.3389/fimmu.2018.02466
3. Walsh EE, Peterson DR, Falsey AR. Human Metapneumovirus Infections in Adults: Another Piece of the Puzzle. Arch Intern Med. 2008;168(22):2489–2496.  
4. Feng, Y., He, T., Zhang, B. et al. Epidemiology and diagnosis technologies of human metapneumovirus in China: a mini review. Virol J 21, 59 (2024). 
5. Nokso-Koivisto J, Hovi T, Pitkäranta A. Viral upper respiratory tract infections in young children with emphasis on acute otitis media. Int J Pediatr Otorhinolaryngol [Internet]. 2006;70(8):1333–42. 0358
6. Costa-Filho RC, Saddy F, Costa JLF, Tavares LR, Castro Faria Neto HC. The Silent Threat of Human Metapneumovirus: Clinical Challenges and Diagnostic Insights from a Severe Pneumonia Case. Microorganisms. 2025; 13(1):73. 
7. Philippot Q, Rammaert B, Dauriat G, et al. Human metapneumovirus infection is associated with a substantial morbidity and mortality burden in adult inpatients. Heliyon. 2024;10(13):e33231. Published 2024 Jun 18. doi:10.1016/j.heliyon.2024.e33231
8. Philippot Q, Rammaert B, Dauriat G, Daubin C, Schlemmer F, Costantini A, et al. Human metapneumovirus infection is associated with a substantial morbidity and mortality burden in adult inpatients. Heliyon [Internet]. 2024;10(13):e33231.
9. Haas LE, Thijsen SF, van Elden L, Heemstra KA. Human metapneumovirus in adults. Viruses. 2013;5(1):87-110. Published 2013 Jan 8. doi:10.3390/v5010087
10. Panda S, Mohakud NK, Pena L, Kumar S. Human metapneumovirus: review of an important respiratory pathogen. Int J Infect Dis [Internet]. 2014;25:45–52. 
11. Geppe NA, Zaplatnikov AL, Kondyurina EG, Chepurnaya MM, Kolosova NG. The Common Cold and Influenza in Children: To Treat or Not to Treat?. Microorganisms. 2023;11(4):858. Published 2023 Mar 28.