HMPV: A known virus, not a mystery

Recent reports of a Human Metapneumovirus (HMPV) outbreak in China have triggered global concerns, with echoes of the early Covid-19 pandemic raising speculation about a potential health emergency. However, HMPV is not a new or mysterious virus. It has been well-documented for decades as a significant cause of respiratory illness in children, elderly and immunocompromised individuals.

Identified in 2001 at Erasmus Medical Center in the Netherlands, HMPV was initially isolated from children with respiratory illnesses. Published in Nature Medicine, this study indicated all Dutch children were exposed to HMPV by the age of five. Retrospective analyses, however, suggest HMPV has been circulating in humans for 50 years.

HMPV belongs to the Pneumoviridae family along with respiratory syncytial virus (RSV) and the Metapneumovirus genus. This enveloped, single-stranded negative-sense RNA virus has two genetic lineages, A and B, further divided into six sublineages: A1, A2.1, A2.2.1, A2.2.2, B1 and B2. Emerging sublineages A2.2.1 and A2.2.2, were recently identified in pediatric respiratory infections in South India, as reported by the International Society of Infectious Diseases in 2025.

A Virology Journal 2009 genetic study by Vanderbilt University suggests HMPV diverged from Avian Metapneumovirus 200–400 years ago via zoonotic spillover from an avian reservoir, with phylogenetic evidence indicating a spillover event around 200 years ago, emphasizing HMPV’s long-standing presence in human populations.

Symptoms, risk groups and treatment

HMPV is a common etiological agent of respiratory tract infections, affecting infants, children under 15, the elderly, and immunocompromised individuals. Nearly all children are exposed by age five, with reinfections occurring throughout life. According to the US Centers for Disease Control and Prevention (CDC), it spreads via respiratory droplets, close contact, or contaminated surfaces, similar to the transmission of SARS-CoV-2, with an incubation period of 3–6 days. Symptoms vary from mild cough, nasal congestion, fever, and breath shortness to severe pneumonia, bronchiolitis, asthma exacerbations, especially in high-risk groups.

Infants and young children are prone to severe bronchiolitis and pneumonia. The elderly, often with comorbidities like asthma, may experience complications. Immunocompromised individuals face prolonged or severe illness, and pregnant women are at risk of respiratory complications that could affect both maternal and fetal health.

No specific antiviral treatment or vaccine exists for HMPV. Management relies on supportive care, supplemental oxygen, antipyretics and intravenous hydration when needed.

Seasonal outbreaks

HMPV is a seasonal respiratory virus, primarily circulating during late winter and early spring in temperate regions, similar to influenza and RSV. Recent reports of increased cases in China and parts of Asia align with this seasonal pattern. US CDC data also highlight annual outbreaks during these months, influenced by climatic conditions.

Despite comparisons to the Covid-19 pandemic, HMPV is not a novel virus. Identified over two decades back, it has been extensively studied, with over 300 PubMed scientific articles available. While it causes localized outbreaks, its transmission dynamics and clinical severity do not indicate pandemic potential. For instance, HMPV was the predominant virus during the 2002–2003 winter in Norwegian children hospitalized for respiratory infections, as reported in The Pediatric Infectious Disease Journal. Severe pneumonia occurred in some cases, but widespread outbreaks have remained limited to specific populations.

HMPV outbreaks have been documented globally, including Israel (2003), Japan (2003–2004), South Africa (2009-2013), Nicaragua (2011-2016), Western Sydney (2018), South Korea (2022), India (2022), China (2017-2023) and various regions. In Pakistan, HMPV accounted for 5–7 percent of pneumonia admissions in children at Aga Khan University Hospital (2009–2012). HMPV causes 5–10 percent of pediatric acute respiratory infections (ARIs) hospitalizations and is the second most common viral pathogen in certain settings. ARIs are a major global public health problem, causing significant morbidity and mortality, particularly in children.

A 2019 study at Nepal’s Kanti Children’s Hospital revealed a prevalence of 13 percent among children with ARIs, with infections more frequent in those under three years old (22 percent). Symptoms like cough and fever were universally observed.

Besides, data from Nepal’s Sarlahi district (2011–2014) detected HMPV in five percent of infants, identifying three genotypes (A2, B1, B2). A recent Chinese CDC analysis ranked HMPV second among 11 respiratory viruses affecting children under 15 years, with a positivity rate of 6.2 percent in influenza-like illness.

These findings reflect a seasonal uptick, not an unprecedented surge. Factors like colder weather and increased indoor crowding contribute to HMPV’s seasonal prevalence.

Covid-19 lessons

The Covid-19 pandemic highlighted the importance of preparedness, evidence-based communication and robust public health strategies in managing infectious disease outbreaks. While HMPV does not pose the same threat as Covid-19, its current attention emphasizes the need to apply these lessons. Strengthened surveillance systems are essential for early detection, while public education can counter misinformation, reduce anxiety and encourage preventive behaviors. Investment in research on HMPV’s pathogenesis, treatments and vaccine development is key to mitigating its long-term impacts and bolstering public health resilience.

Precautions

The rise in HMPV cases in China and India warrants vigilance but not alarm. Vulnerable populations—infants, rural children, immunocompromised individuals—are particularly at risk, in regions with limited healthcare resources like Nepal. Preventive measures, supportive care and community-driven initiatives are critical to minimizing HMPV’s burden.

Between 2011 and 2014, HMPV infections in rural southern Nepal were associated with adverse outcomes, including an increased risk of small-for-gestational-age births in pregnant women. Interventions targeting febrile respiratory illness in pregnancy could improve maternal and neonatal health in resource-limited settings.

Hygiene practices, regular handwashing and respiratory etiquette, alongside isolation during illness, can reduce HMPV transmission. Enhanced diagnostic capabilities and heightened awareness will support disease management and safeguard at-risk groups.

Policymakers, healthcare providers and community leaders must collaborate to strengthen surveillance systems, improve diagnostics and develop effective preventive strategies. Public health messaging should prioritize education and reassurance, focusing on practical actions to protect vulnerable populations. By taking informed and measured steps, HMPV’s impact can be effectively mitigated, fostering resilience against future viral outbreaks.

 

The author is a researcher with a PhD degree at Nexus Institute of Research and Innovation