Understanding Human Metapneumovirus (HMPV): A rising global concern

Introduction

Human Metapneumovirus (HMPV) is garnering attention as outbreaks emerge globally, including a reported surge in cases among children in China. While not new, this respiratory virus poses a significant public health concern, particularly for vulnerable populations like young children, the elderly, and immuno-compromised individuals.

This article explores HMPV’s origins, transmission, current global impact, and preventive measures.

Respiratory Viruses

What is HMPV

Discovered in 2001, HMPV has been circulating globally for decades, causing respiratory infections ranging from mild cold-like symptoms to severe illnesses. Its clinical presentation often overlaps with other respiratory viruses like influenza and respiratory syncytial virus (RSV).

Also Read: HMPV not likely a concern for India but a 'winter challenge'

HMPV is spread through respiratory droplets when an infected person coughs, sneezes, or talks. It can also be transmitted via contaminated surfaces, making hygiene practices critical in curbing its spread.

The Current Situation

Recent reports from China have highlighted a rise in HMPV cases, primarily affecting children under 14. Hospitals in affected regions have seen increased patient volumes for respiratory illnesses, including HMPV, influenza, Mycoplasma pneumoniae, and COVID-19. China has been a breeding ground for deadly viruses such as COVID-19, bird flu, and SARS, and China proved to be non-cooperative in sharing information so that other nations take necessary precautions to prevent any spreading.

Globally, HMPV infections tend to peak in late winter and spring. While seasonal, the virus’s impact is significant in high-risk populations, often leading to hospitalization.

Symptoms and Severity

HMPV infections typically present with symptoms like:

• Fever
• Cough
• Runny nose
• Sore throat
• Wheezing
• Shortness of breath
• Fatigue

For most, these symptoms resolve without complications. However, in high-risk groups, the virus can lead to bronchitis or pneumonia, requiring medical intervention.

Global Response and Challenges

Despite being a known pathogen for over 20 years, no vaccine exists for HMPV. Developing effective vaccines for respiratory viruses remains a challenge due to the rapid mutation rates of these pathogens. Current public health efforts focus on surveillance, early detection, and public awareness to minimize the spread.

Preventive Measures

1. Personal Hygiene:
   • Wash hands frequently with soap and water for at least 20 seconds.
   • Use alcohol-based hand sanitizers when soap and water are unavailable.
2. Respiratory Etiquette:
   • Cover your mouth and nose with a tissue or elbow when coughing or sneezing.
   • Dispose of tissues immediately and sanitize hands.
3. Avoid Close Contact:
   • Maintain distance from individuals exhibiting symptoms of respiratory illness.
   • Avoid crowded and poorly ventilated areas.
4. Clean and Disinfect:
   • Regularly disinfect high-touch surfaces such as doorknobs, phones, and countertops.
5. Boost Immune Health:
   • Eat a balanced diet rich in vitamins and minerals.
   • Stay hydrated and get adequate sleep.
   • Engage in regular physical activity.

Natural and Herbal Remedies for Prevention and Coping with HMPV

1. Immune-Boosting Herbs:
   • Echinacea: Known for its antiviral properties, it helps reduce the severity and duration of respiratory infections.
   • Elderberry: Rich in antioxidants, it can support the immune system and combat flu-like symptoms.
2. Herbal Teas:
   • Ginger Tea: Helps soothe the throat and alleviate congestion.
   • Tulsi (Holy Basil) Tea: Known for its antimicrobial and anti-inflammatory properties.
3. Turmeric Milk:
   • A traditional remedy with curcumin, which has anti-inflammatory and immune-boosting benefits.
   • Mix a teaspoon of turmeric in warm milk and consume before bedtime.
4. Steam Inhalation:
   • Add essential oils like eucalyptus or peppermint to hot water and inhale the steam to relieve congestion.
5. Honey and Lemon:
   • A mixture of honey and lemon in warm water can soothe a sore throat and provide vitamin C to boost immunity.
6. Probiotics:
   • Incorporate yogurt or other probiotic-rich foods to promote gut health, which is closely linked to immune function.
7. Zinc and Vitamin C:
   • Increase intake of zinc-rich foods (pumpkin seeds, nuts) and vitamin C (citrus fruits, bell peppers) to strengthen immunity.

When to Seek Medical Help

If symptoms worsen or include high fever, severe breathing difficulty, or persistent chest pain, seek medical attention promptly. Early diagnosis and treatment are crucial, especially for high-risk groups.

In short, While HMPV is not a new threat, its potential to cause widespread illness, particularly among vulnerable populations, underscores the need for vigilance. Public health systems worldwide must enhance surveillance, invest in vaccine research, and educate communities about preventive measures to mitigate its impact.

Staying informed and adhering to basic hygiene practices are our best defenses against HMPV and similar respiratory viruses.

Scientific Characteristics of HMPV and RNA Viruses

Human Metapneumovirus (HMPV), like many RNA viruses, has a propensity for mutation and adaptation, which can lead to changes in its virulence or transmissibility. Understanding HMPV in the context of other RNA viruses, including SARS-CoV-2 (COVID-19) and avian influenza (bird flu), reveals how these pathogens evolve and sometimes interact, raising questions about genome swapping and enhanced virulence.

Genomic Structure

HMPV is a single-stranded, negative-sense RNA virus from the Pneumoviridae family, closely related to Respiratory Syncytial Virus (RSV). Its genome encodes several proteins essential for replication and immune evasion.

Also Read: China calls HMPV 'winter occurrence', no cause for alarm, says India

Mutation Rates

RNA viruses are characterized by high mutation rates due to the lack of proofreading during RNA replication. This allows rapid adaptation to environmental pressures, such as host immune defenses or antiviral treatments.

Comparison with Other RNA Viruses

HMPV's mutation rate is moderate compared to SARS-CoV-2 and influenza, but its evolutionary trajectory can still lead to significant phenotypic changes over time.

Potential for Genome Swapping and Reassortment

Mechanisms of Viral Evolution

1. Mutation: A gradual accumulation of genetic changes.
2. Recombination: Exchange of genetic material between viruses during co-infection.
3. Reassortment: Exchange of entire genomic segments, primarily in segmented RNA viruses like influenza.

HMPV and Genome Swapping

HMPV lacks a segmented genome, making reassortment unlikely. However, recombination between co-circulating strains of HMPV or with related viruses (e.g., RSV) is theoretically possible but has not been conclusively demonstrated.

Comparison with SARS-CoV-2 and Influenza

• SARS-CoV-2 frequently undergoes recombination, which has contributed to the emergence of variants with enhanced transmissibility or immune evasion.
• Influenza’s segmented genome allows for frequent reassortment, a major driver of its pandemic potential (e.g., the H1N1 2009 pandemic).

Impact of Co-Circulating Viruses

Co-Infections and Viral Evolution

• During the COVID-19 pandemic, disruptions to immunity and healthcare systems may have altered the epidemiology of other viruses like HMPV.
• Immune suppression or modulation caused by SARS-CoV-2 infection could facilitate more severe HMPV infections.
• Co-infections with SARS-CoV-2, influenza, or HMPV might theoretically create opportunities for recombination, though this is uncommon among unrelated RNA viruses.

Post-COVID-19 Effects on HMPV

• Increased surveillance after COVID-19 might have heightened the detection of HMPV.
• Immune system alterations (e.g., “immune debt” from reduced virus exposure during lockdowns) may have contributed to more severe HMPV cases.

Future Risks and Monitoring

1. Enhanced Virulence: Mutation-driven evolution could lead to strains of HMPV with higher transmissibility or pathogenicity.
2. Recombination Events: While rare for HMPV, recombination with related viruses remains a possibility under specific circumstances.
3. Zoonotic Potential: HMPV is thought to have originated from birds. Continuous monitoring for cross-species transmission is crucial.

Key Takeaway

HMPV’s current rise in severity might reflect a combination of natural viral evolution, immune system changes post-COVID-19, and increased viral interactions in the human population. Understanding these dynamics requires ongoing genomic surveillance and research into co-infections.

Viral Combination

The potential combination of Human Metapneumovirus (HMPV) with SARS-CoV-2 or other highly virulent viruses raises significant concerns due to the possibility of creating a pathogen with enhanced transmissibility, virulence, or immune evasion capabilities. However, the likelihood and consequences of such a combination depend on several biological and ecological factors. Below is an analysis of what such a scenario might entail:

Mechanisms of Viral Combination

1. Recombination
2. Reassortment
3. Viral Synergy (Co-Infection)

• Recombination occurs when two viruses co-infect the same host cell and exchange genetic material. This is more likely in viruses with similar genomic structures or evolutionary lineages.
• HMPV and SARS-CoV-2 belong to different virus families (Pneumoviridae and Coronaviridae, respectively) and have distinct genome architectures. This makes recombination between them highly improbable.
• Reassortment involves swapping of genome segments, typically seen in segmented RNA viruses like influenza. Since neither HMPV nor SARS-CoV-2 has a segmented genome, this is not applicable.
• Co-infection with HMPV and SARS-CoV-2 could lead to synergistic effects, where one virus enhances the pathogenicity or replication of the other.
• For example, SARS-CoV-2 might suppress the immune system, allowing HMPV to cause more severe disease or vice versa.

Potential Consequences of a Combination

1. Enhanced Virulence
2. Increased Transmissibility
3. Immune Evasion
4. Disease Severity

• A virus that combines the immune evasion capabilities of SARS-CoV-2 with the respiratory tropism of HMPV could lead to more severe infections, particularly in vulnerable populations.
• Such a hybrid might exploit immune system weaknesses, causing more profound lung damage or multi-organ involvement.
• If a combined virus acquired the transmissibility of SARS-CoV-2, it could spread rapidly, leading to widespread outbreaks.
• The high mutation rate of RNA viruses could accelerate the evolution of such a pathogen.
• A hybrid virus could potentially evade immune responses by combining mechanisms of immune suppression from both parents, complicating vaccine or antiviral development.
• Co-infections are already associated with worse clinical outcomes. For instance, simultaneous infection with HMPV and SARS-CoV-2 could lead to severe respiratory distress or secondary bacterial infections.

Historical Context

• Influenza and Bacterial Pneumonia: During the 1918 flu pandemic, secondary bacterial infections significantly increased mortality.
• SARS-CoV-2 and Influenza: Co-infections during the COVID-19 pandemic occasionally resulted in worse outcomes, emphasizing the dangers of viral synergy.

Mitigation Strategies

1. Surveillance
   • Strengthened global surveillance systems to monitor co-infections and emerging strains.
2. Vaccination
   • Development of vaccines targeting multiple pathogens simultaneously.
3. Antiviral Research
   • Broad-spectrum antivirals effective against multiple respiratory viruses.
4. Public Health Measures
   • Continued emphasis on hygiene, mask-wearing, and limiting co-infection risks through vaccination and preventive care.

While the direct combination of HMPV and SARS-CoV-2 is biologically unlikely due to their differing genetic structures, the possibility of co-infections or synergistic interactions remains concerning. Such scenarios could exacerbate disease severity, overwhelm healthcare systems, and complicate treatment efforts. Proactive surveillance, research, and public health strategies are essential to mitigate these risks.

Also Read: After outbreak in China, India's first cases of HMPV reported in Karnataka and Gujarat amid 'national surveillance'

References for further readings

1. van den Hoogen, Bernadette G., Jan C. de Jong, Jozef Groen, Thijs Kuiken, Ronald de Groot, Gijs A. F. S. Berkhout, and Albert D. M. E. Osterhaus. "A Newly Discovered Human Pneumovirus Isolated from Young Children with Respiratory Tract Disease." Nature Medicine 7, no. 6 (2001): 719–24.
2. Centers for Disease Control and Prevention. "Human Metapneumovirus (HMPV)." Last reviewed August 31, 2021.
3. Zhu, Na, Dingqiang Zhang, Wenling Wang, Xingwang Li, Bo Yang, Jingdong Song, et al. "A Novel Coronavirus from Patients with Pneumonia in China, 2019." New England Journal of Medicine 382, no. 8 (2020): 727–33.
4. Taubenberger, Jeffery K., and David M. Morens. "1918 Influenza: The Mother of All Pandemics." Emerging Infectious Diseases 12, no. 1 (2006): 15–22.
5. National Institute of Health. "HMPV and Respiratory Illness." NIH Research Matters, June 2, 2023.
6. World Health Organization. "RNA Virus Evolution and Its Implications for Public Health." Weekly Epidemiological Record 92, no. 4 (2017): 37–48.
7. Shen, Minyi, Yunhao Xiao, and Xiang Wei. "The Impact of COVID-19 on Immune Systems and Future Viral Infections." Journal of Immunology Research 2021 (2021): Article ID 5517067.
8. Ison, Michael G. "Respiratory Viral Infections in Transplant Patients: The Role of the Community Respiratory Virus." Clinical Infectious Diseases 50, no. 6 (2010): 817–19.

HMPV, SARS-CoV-2, and potential viral interactions

1. Chen, Na, Min-Qi Zhou, Hua-Dong Zhang, and Yan-Wen Gong. "Co-Infection with SARS-CoV-2 and Influenza Virus in the Early Stage of the COVID-19 Pandemic: A Systematic Review." Frontiers in Public Health 10 (2022): Article 842311.
2. Zheng, Ye, Qiwei Wang, and Zhiwei Li. "Potential Synergies and Competition between SARS-CoV-2 and Other Respiratory Viruses in Co-Infections." Frontiers in Immunology 12 (2021): Article 784641.
3. V'kovski, Philip, Annika Kratzel, Sandra Steiner, Hanspeter Stalder, and Volker Thiel. "Coronavirus Biology and Replication: Implications for SARS-CoV-2." Nature Reviews Microbiology 19, no. 3 (2021): 155–70.
4. van den Hoogen, Bernadette G., Ronald de Groot, and Albert D. M. E. Osterhaus. "History and Emergence of Human Metapneumovirus: Understanding Its Biological Characteristics and Public Health Impact." Clinical Microbiology Reviews 16, no. 4 (2003): 615–27.
5. Nickbakhsh, Sema, Laila Thorburn, Richard J. W. von Wissmann, Rebecca McMenamin, Rory N. Gunson, and Pablo R. Murcia. "Viral Interference between Respiratory Viruses: A Protective Effect against Influenza A Virus Subtype Infection?" Journal of Infectious Diseases 219, no. 5 (2019): 627–30.
6. Taubenberger, Jeffery K., and David M. Morens. "1918 Influenza: The Mother of All Pandemics." Emerging Infectious Diseases 12, no. 1 (2006): 15–22.
7. Alsharif, Waleed, and Ahmad Qurashi. "Effectiveness of COVID-19 Vaccines in Reducing Severe Cases and Mortality: A Systematic Review." Cureus 14, no. 6 (2022): Article e26169.