Human Metapneumovirus (HMPV) in the UK: Understanding the Virus and Testing Methods

Human Metapneumovirus (HMPV) is a relatively recently identified respiratory virus that has been increasingly recognized as a cause of respiratory infections, especially in vulnerable populations. Though HMPV infections have been known for nearly two decades, they have only recently gained attention due to their impact on health systems and the growing awareness of viral respiratory illnesses. In the UK, like in many other parts of the world, HMPV is emerging as a significant cause of respiratory illness, particularly among children, the elderly, and those with compromised immune systems.

In this blog, we’ll explore what HMPV is, its symptoms, transmission, the prevalence of the virus in the UK, and how the virus is diagnosed through testing methods.

What is HMPV?

Human Metapneumovirus (HMPV) is a member of the Metapneumovirus family, which also includes other respiratory viruses like respiratory syncytial virus (RSV). The virus was first discovered in 2001 by Dutch scientists and has since been recognized as a common cause of respiratory illness, particularly in young children, older adults, and individuals with underlying health conditions.

HMPV primarily affects the respiratory tract, causing infections that range from mild upper respiratory tract symptoms to severe lower respiratory tract infections, such as pneumonia and bronchiolitis. The virus can also lead to hospitalisations, especially in vulnerable groups.

Key Facts About HMPV:

Symptoms: HMPV infection presents similarly to other respiratory viruses, with symptoms that can include fever, cough, nasal congestion, sore throat, shortness of breath, and wheezing. In more severe cases, it can lead to pneumonia or bronchiolitis, requiring hospital care.
  
Transmission: The virus is spread through respiratory droplets when an infected person coughs or sneezes, or through direct contact with contaminated surfaces. The virus can survive on surfaces for several hours, making it highly transmissible in public spaces.

Seasonality: HMPV infections typically peak during the winter and spring months, although outbreaks can occur throughout the year.

HMPV in the UK: Growing Concern

In the UK, HMPV is becoming an increasing concern, particularly as it shares similarities with other viruses like influenza, RSV, and COVID-19. The rise in cases of respiratory illness due to HMPV has coincided with the easing of pandemic restrictions, which led to an increased circulation of viruses in the community.

The UK Health Security Agency (UKHSA) has been monitoring respiratory viruses closely, and while HMPV is still relatively underreported compared to other viruses like influenza, its role in respiratory illness is gaining more recognition. Studies suggest that HMPV is a significant contributor to seasonal respiratory infections in both children and adults.

Impact on Vulnerable Groups

HMPV is especially concerning for:

Children under 5 years: Young children, particularly those under two years of age, are at a higher risk of developing severe respiratory illnesses such as bronchiolitis and pneumonia.
  
Older adults: Elderly individuals, particularly those with underlying health conditions like chronic obstructive pulmonary disease (COPD) or heart disease, are more likely to develop severe complications from the virus.

Immunocompromised individuals: Those with weakened immune systems, including people undergoing cancer treatment or with organ transplants, are at heightened risk of severe illness from HMPV.

How to Test for HMPV

Testing for HMPV involves detecting the virus through various laboratory methods. Since the symptoms of HMPV infection overlap with those of other respiratory viruses, laboratory testing is crucial for accurate diagnosis.

1. PCR (Polymerase Chain Reaction) Testing

PCR is the most widely used and reliable method for diagnosing HMPV infections. It is a molecular test that detects the genetic material (RNA) of the virus from a patient’s respiratory sample, such as a throat swab, nasopharyngeal swab, or sputum. PCR tests are highly sensitive and specific, meaning they can detect low levels of viral RNA and differentiate HMPV from other respiratory pathogens.

How It Works: A sample is collected from the patient’s respiratory tract using a swab. The sample is then sent to a laboratory where it undergoes PCR amplification to identify the presence of HMPV RNA.
  
Advantages: PCR testing is quick, highly accurate, and can differentiate HMPV from other viruses like influenza, RSV, and COVID-19.

2. RT-PCR (Reverse Transcription PCR)

RT-PCR is a subtype of PCR testing specifically used for RNA viruses like HMPV. It involves the conversion of viral RNA into DNA (reverse transcription), followed by amplification and detection.

3. Viral Culture

Viral culture involves growing the virus in a laboratory setting. This method can be used to confirm the presence of the virus, but it is not commonly used for routine diagnosis due to its longer turnaround time and more complex procedures.

4. Rapid Antigen Testing

Rapid antigen tests are another option for detecting HMPV, although they are not as sensitive or specific as PCR tests. These tests work by detecting specific proteins from the virus in a respiratory sample. While they are faster and more convenient, they are less accurate and are typically used for influenza and COVID-19 rather than HMPV.

5. Serology Tests

Serology tests measure the presence of antibodies against HMPV in the blood. These tests are typically used for research purposes and are not commonly used in routine clinical practice for diagnosing acute infections, as they indicate past exposure rather than current infection.

When Should You Get Tested for HMPV?

If you or a loved one is experiencing symptoms such as persistent cough, fever, difficulty breathing, or wheezing—especially if you fall into a high-risk group—it’s important to consult a healthcare provider. Testing for HMPV may be recommended if your doctor suspects a viral infection based on your symptoms and the timing of illness.

If you are a parent of a young child or the caregiver of an elderly person, be particularly vigilant. Severe symptoms or difficulty breathing should be addressed promptly by healthcare professionals.

In the UK: Public Health Guidelines

GP Consultation: If you are experiencing symptoms of a respiratory infection, it is always advisable to consult with your GP. They will assess your symptoms and, if necessary, refer you for testing.

Hospital Testing: If symptoms become severe, particularly for vulnerable individuals, hospitals may conduct tests for HMPV along with other common respiratory viruses to determine the exact cause of the infection.

Conclusion

Human Metapneumovirus (HMPV) is a growing concern in the UK, particularly during the winter months when respiratory infections peak. While the virus generally causes mild symptoms, it can lead to severe illness in vulnerable groups such as young children, older adults, and immunocompromised individuals. Early and accurate diagnosis through PCR testing is essential to properly manage the infection and differentiate it from other viruses.

As healthcare systems continue to adapt to the challenges posed by respiratory viruses, including HMPV, public awareness and timely testing will be key in reducing the burden of respiratory infections in the UK.

If you suspect that you or someone in your care may have HMPV, be sure to seek professional medical advice and get tested to ensure proper treatment and care.