Metapneumovirus was once unknown to doctors


Human Metapneumovirus (hMPV) is the infection we didn't know we had. There are many viruses that cause colds - and also ones that lead to asthma flare-ups, bronchitis, pneumonia, and other respiratory illnesses. We just don't know what all of them are.

Metapneumoviruses are usually mild, but some cases can be serious. Some infections lead to asthma attacks that can be serious for some.

It wasn't until this century that the virus was found.

 In 2001, hMPV was first identified in the Netherlands. It was seen among samples from children with respiratory infections. It was quickly was found in other parts of the world. It was realized that 

It was commonly found in children with asthma exacerbations, up to 8% presenting to hospital in one Finnish study. It was also found in a study to cause more respiratory illness than we imagined; it was seen in about 10% of respiratory samples collected in a study one winter for respiratory disease. Others have found it less commonly; a little over 1 in 50 samples that were negative for influenza and RSV (another respiratory virus). Regardless, it is a pretty common virus.

In fact, it is so common that almost all of us have been infected at least once by the age of 5.

Thing is, it had been there for years. Looking back over old blood samples, it was clear that the virus had been circulating among people for at least 50 years.

For most cases of common respiratory infections, including community-acquired pneumonia, there is a never a diagnosis of what bug, whether virus or bacteria, is causing it. hMPV is part of the likely many viruses that cause our colds, and even our pneumonia, that we never diagnose.

What does it cause?

Human Metapneumovirus (hMPV) causes infections in upper and lower respiratory tracts. That is to say, it can cause a cold or it can cause bronchitis or pneumonia.

The infection occurs in all ages. It can be more severe in infants and the elderly as their immune systems cannot handle the virus as well. In some, it can cause wheezing or asthma flare-ups, make it difficult to breathe and lead to pneumonia, a deep infection in the lungs.

What are the symptoms?

The symptoms are much the same as other respiratory viruses. It would be difficult to distinguish an hMPV infection from other colds, bronchitis infections, and viral pneumonia.

Not everyone has a fever. Only about half do. Some may just have wheezing. It is also common with earaches.

An upper respiratory tract infection may include:

  • Cough
  • Fever
  • Runny nose
  • Stuffy nose
  • Sore throat
  • Earache

A lower respiratory tract infection, leading to severe disease may lead to

  • High fever
  • Bad cough
  • Problems breathing
  • Breathing very fast
  • Wheezing, Asthma Flare
  • Muscle aches
  • Vomiting, Diarrhea

How do you know you have hMPV?

Some labs can run a test on a nasal swab. Many cases are never diagnosed, never tested for. Most who have it do not know that their infection is caused by hMPV.

How is Human Metapneumovirus Treated?

There is usually no reason to know specifically which virus is causing the infection. Like with many viruses, there is no specific treatment for hMPV. For influenza and a few other viruses, there are specific treatments, so diagnosis can change how the illness would be treated.

All care for hMPV is supportive, making sure the patient is comfortable - and is breathing well. Those who develop wheezing may need inhalers, nebulizers, or breathing treatments. Others may need other help breathing. Usually, though patients rest up and maybe take a medication that reduces fever. Because this infection is caused by a virus, if there is no additional bacterial infection, antibiotics - which only treat bacteria - will not help. 

When does it spread?

Late winter to early spring. Most cases are from December to May in the Northern Hemisphere.

How do you prevent the spread of hMPV?

Please cover your mouth and nose when you sneeze or cough. You should do this with a tissue (that you then throw away) or your elbow or upper sleeve. Please wash your hands thoroughly.

Is there a vaccine?


Who gets infected?

Most are first infected by age 5, though some can be reinfected. The mean age of those who test positive is 20 months. Among adults, those at most risk are the elderly, those with weakened immune systems, such as transplant patients, and those with COPD (emphysema). The disease can be particularly dangerous, and even deadly, in those who are very immunocompromised.

What sort of virus is it?

It is a Paramyxovirus. This makes it a negative-sense, single-stranded RNA virus. Other relatives in this family of viruses include Measles and Mumps.

Are there different types of Metapneumoviruses?

Yes, among Human MPV there are different lineages - A1, A2, B1, and B2. 

There is also Avian MPV. It is thought that the human variant diverged from the bird variety in the last 200 years, based on genetic analysis.

Is this the only new human respiratory virus?

Nope. With better molecular lab techniques we are better at identifying viruses that cause human illness - or are part of the collection of viruses we carry with us every day, our virome. We are also identifying new outbreaks more quickly - especially when they quickly spread with air travel and well-paved roads. In recent years, SARS and MERS have been identified in outbreaks, as well as less notable viruses like human bocavirus and other human coronaviruses (which belong to the same family as MERS and SARS).

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