Respiratory infections are a major global health concern, especially for young children. In fact, they are the second leading cause of death among children under five. Acute Respiratory Infections (ARI) are among the most common illnesses in children and are particularly deadly in Sub-Saharan Africa and South Asia.
At this point, Human Metapneumovirus (HMPV) enters the stage. Discovered in 2001 by Van den Hoogen and his team in the Netherlands, HMPV was identified when researchers analyzed respiratory samples collected over the years and found a pathogen that did not match any known respiratory virus. This led to the recognition of HMPV as a distinct virus.
Last month, China’s disease control center launched a monitoring system for unexplained pneumonia cases and warned of a rise in respiratory infections throughout the winter. Since mid-December, infection rates have been climbing, with a noticeable increase in Human Metapneumovirus (HMPV) cases, especially among children under 14.
HMPV belongs to the Pneumoviridae family and is a negative-sense, single-stranded RNA virus closely related to Respiratory Syncytial Virus (RSV). But how does it work, how does it spread, and how can we protect ourselves? Let’s take a closer look.
HMPV belongs to the same virus family as RSV, measles, and mumps, and it’s often mistaken for RSV since they cause similar symptoms. The key difference? HMPV tends to be more severe in babies aged 6-12 months, while RSV poses a higher risk for infants under 6 months.
Genetic and Molecular Structure of the Virus
The HMPV genome is approximately 13,000 nucleotides long and contains 8 genes. Moreover, these genes encode 9 different proteins, including:
- Nucleoprotein (N) → Protects the viral RNA.
- Phosphoprotein (P) → Assists the polymerase enzyme.
- Matrix protein (M) → Forms the structure of the virus.
- Fusion protein (F) → Helps the virus enter cells. It closely resembles RSV’s F protein.
- Glycoprotein (G) → Allows the virus to bind to cells, but is highly variable genetically.
- Small hydrophobic protein (SH) → Scientists do not fully understand its function yet.
- L (Large protein) and M2 (Matrix protein 2) → Form the RNA polymerase responsible for viral replication.
HMPV is classified into two major groups (A and B), which are further divided into A1, A2, B1, and B2 subtypes. Scientists estimate that this virus has been evolving for 200-400 years.
How Does HMPV Replicate?
HMPV infects the respiratory tract, where it replicates and spreads. The process follows these key steps:
- Attachment → The virus binds to cells using G protein.
- Entry → The F protein facilitates membrane fusion, allowing the virus to enter.
- Replication →The host cell releases the viral RNA and produces new viral proteins.
- Spread → New viruses bud off from the infected cell and spread to others.
Once inside the body, HMPV rapidly multiplies and causes inflammation in the respiratory tract.
How Common Is HMPV?
HMPV is highly prevalent worldwide and follows a seasonal pattern, peaking after RSV and influenza.
- In the Northern Hemisphere → Most infections occur between January and March.
- In the Southern Hemisphere → Peaks typically occur in June and July.
Studies show that by the age of five, 90-100% of children have been infected at least once. Since immunity does not provide lifelong protection, reinfection is possible throughout life. The highest risk groups include:
- Infants and young children
- Elderly individuals
- Immunocompromised patients (e.g., cancer patients, organ transplant recipients)
Symptoms and Transmission
The symptoms of this virus are highly similar to those of RSV and the flu.
- Mild cases → Runny nose, cough, and mild fever.
- Severe cases → Bronchiolitis, pneumonia, breathing difficulties, and hypoxia.
- Immunocompromised individuals → May develop life-threatening lung infections.
- Some patients → Experience asthma-like airway hypersensitivity.
HMPV spreads through:
- Respiratory droplets (coughing, sneezing)
- Direct contact with infected individuals
- Touching contaminated surfaces and then touching the face
How Is HMPV Diagnosed?
HMPV cannot be diagnosed based on symptoms alone. Laboratory tests are needed, such as:
- RT-PCR (Reverse Transcription PCR) → The most reliable method, detecting viral genetic material.
- Rapid antigen tests → More convenient but less accurate than RT-PCR.
- Cell culture → Rarely used, as growing HMPV in labs is difficult.
Is There a Treatment for HMPV?
Unfortunately, there is no specific antiviral treatment or approved vaccine for HMPV.
Potential treatments under investigation include:
- Ribavirin and intravenous immunoglobulin (IVIG) → Studied, but efficacy is unclear.
- Monoclonal antibody therapies → Ongoing research.
Are There Any Vaccine Developments?
Scientists are exploring different strategies for an HMPV vaccine:
- Live attenuated vaccines
- Recombinant protein-based vaccines
- Viral vector vaccines
However, due to negative experiences with RSV vaccine trials, researchers are cautious. Future studies will focus on understanding how HMPV evades the immune system and developing effective preventive measures.
HMPV is a widely prevalent but underrecognized respiratory virus that affects people of all ages, especially those in high-risk groups.
Currently, there is no specific treatment or vaccine, but practicing good hygiene and preventive measures can help reduce the risk of infection:
- Wash your hands regularly with soap and water.
- Avoid close contact with sick individuals.
- Cover your mouth when coughing or sneezing.
- Disinfect frequently touched surfaces.
If you experience flu-like symptoms that persist for a long time, consult a doctor. Remember, not every respiratory infection is just a “common cold”!
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Hello! I am Melis Esma Demirbilek, a 3rd year student at Biruni University, Department of Molecular Biology and Genetics. My passion for scientific research and curiosity about biology led me to both academic and social projects. I am currently working as a writer on the Biologyto page, producing current and interesting content about biology. My future goal is to create both academic and social benefit by contributing to scientific studies.
