A new respiratory virus – Human Metapneumovirus (hMPV)

What is the name of the virus and what are its characteristics?

The name of the virus is Human Metapneumovirus or hMPV in short.
This virus, just like most other respiratory viruses, has several different strains. But clinically speaking, I am not sure that piece of information is very significant.
As you can tell from the name, humans are the only reservoir for this virus.

What is the mode of transmission and when does this virus spread?

hMPV spreads through droplets or through contact with secretions, just like most of the other respiratory viruses out there. Healthy children secrete the virus from their respiratory tract even 1-2 weeks after infection, and therefore it is difficult and almost impossible to restrict the spread of this virus.
In fact, we can almost say for certain that most children under the age of five have already been infected with this virus once in their life.
In countries with a warm climate, most of the infections occur towards the end of the winter season, when the RSV seasons comes to an end (find out more about this here).
Nonetheless, this virus can circulate all throughout the year.

How many times can you get infected with hMPV during your life?

Several times.
Usually, the first time you get infected is the most severe and recurrent infections will be milder (a cold). Nonetheless, as you will see below, also adults with underlying chronic conditions can experience complications and severe infection.

What is the incubation time for hMPV?

The incubation time is the duration of time from infection to the manifestation of clinical symptoms and for this virus it is 3-9 days.

What are the signs and symptoms of hMPV?

This virus is a respiratory virus that causes respiratory illness, sometimes the person will experience fever and other times they won’t.
The majority of the morbidity is among children, especially those younger than five years of age where the symptoms are that of upper respiratory tract infection such as a cold as well as lower respiratory tract infection, such as bronchiolitis.
In young babies and older children, it can be a trigger for an asthmatic attack (infancy asthma and real asthma in older children) and stridor.

What are the potential complications of this infection?

The common ones are:
Bronchiolitis and asthmatic attacks that require treatment.
Secondary bacterial infections including bacterial otitis media or pneumonia.
Other complications such as encephalitis are rare.
Some children, especially those aged 6-12 months, require hospitalization for supportive therapy and respiratory support.

Who is at higher risk of developing a more severe course of illness or complications?

Unfortunately, it is the weaker ones among us.
The premature babies, the little babies in their first year of life, children with heart conditions or chronic lung diseases and those who are immune compromised.
In older adults it is quite similar – the elders, the immune compromised and those with lung conditions (COPD) or chronic heart conditions.

So why has this virus been all over the news lately?

Ever since COVID-19, the world has been following respiratory illness outbreaks in China. Towards the end of 2024 there were reports about an exceptional respiratory morbidity in China that seemed to have been caused by this virus.
However, even if there was an exceptionally high rate of hMPV virus in China this past year, it doesn’t seem like this is anything new. This virus emerges every year, and obviously, some years will be worse than others.

How can we detect this virus?

Clinically – even the best of doctors will not be able to tell this virus apart from other respiratory viruses. When pediatricians come across bronchiolitis towards the end of the winter season, after RSV season has passed, we often guess that the cause of it could be hMPV but there are about 10 other respiratory viruses that can cause a similar clinical picture.
A PCR test from the nose can detect the virus. This is usually only done in hospitals.
But with the rise in PCR tests that the outbreak of COVID-19 brought about, I am also familiar with some private clinics that carry a respiratory kit that tests for the common viruses/bacteria, including this one.
This is the future, in my opinion.

How is hMPV treated?

The treatment is supportive.
Anti-pyretic to reduce fever, pain relief, oxygen if a person needs it and fluids for babies that are unable to eat or drink and tend to dehydrate.
Antibiotics are obviously not helpful when it comes to viral illnesses and are only used when there is a concern for a secondary bacterial infection.

How can we prevent this viral illness?

Just like every other respiratory virus – make sure to wash your hands well and avoid contact with or inhaling droplets (saliva) of an infected individual.
This is obviously very difficult, because people with recurrent infections can be quite infectious even with minimal symptoms, such as a mild cold.

What about a vaccine?

We do not have a vaccine for this virus.

When can children go back to daycare or school after an hMPV infection?

I have to make this clear. In about 99% of the cases, we will not know that what the child was this specific virus that has caused their infection and therefore the answer is generic, you can find it in our chapter about returning to educational institutions after an illness.
A child can go back once they are free of fever for 24 hours, are feeling well, and are not experiencing a significant cough (frequent or prolonged cough attacks).
This is pretty general, but it is impossible to give specific guidelines for every single virus out there.

In summary, I almost can’t believe we have reached a point where we have dedicated a chapter about this specific virus. But since the media really wanted to frighten you parents, it was worth writing it for your reassurance. It is obvious to all of us, that just like this virus, there are 10 others (or 50) that can potentially cause illness in humans.
So, it’s good to get yourself familiar with it and to know about it. But please, do not stress!