A Look at Human Metapneumovirus — a Respiratory Virus You've Likely Had Without Knowing

Human Metapneumovirus (HMPV) is a respiratory virus that may not be on most folk’s radars, but it’s more common than you think — and chances are, you’ve already had it.

A recent “outbreak” in northern China has brought HMPV into the spotlight, raising questions about its significance.

Frank Esper, M.D., a pediatric infectious disease specialist at Cleveland Clinic Children’s Hospital, provides his insights into this virus.

Esper

HMPV is similar to common respiratory illnesses such as colds, the flu and Respiratory Syncytial Virus (RSV). Its symptoms include coughing, wheezing, a runny nose and a sore throat.

Although most cases are mild, certain groups — including young children, older adults and those with weak immune systems — face a higher risk of developing severe illness.

According to the Cleveland Clinic, children under five are especially vulnerable due to their developing immune systems.

First discovered in the Netherlands roughly 24 years ago, HMPV belongs to the same viral family as RSV.

Esper, who helped discover the virus during his fellowship at Yale-New Haven Hospital, noted that HMPV likely existed and infected humans for hundreds of years, however, the tools and technology to detect these viruses have only become available in the last few decades.

As “sister” viruses, HMPV and RSV share many characteristics.

Both cause upper and lower respiratory tract infections and can lead to conditions such as viral pneumonia and bronchiolitis.

In children, airway inflammation may result in wheezing and difficulty breathing. Adults with chronic lung conditions, such as asthma or COPD, are also at risk for complications.

Esper shared that while symptoms of the two viruses are similar, their seasonal occurrence differs. RSV typically surges in December and January, while HMPV is more common in March and April.

“They (HMPV and RSV) have a very sophisticated dance,” Esper said. “So, it's not just temperature, but it also has to do with immune priming — about when the susceptibility is.

“There's a lot that goes to when the seasonality of a virus (is). Temperature is one of those parts, but there's actually more than that. They work together somehow, we haven't figured out how.”

Accurate diagnosis requires molecular tests like PCR to detect the virus’s genetic material.

As far as spreading, HMPV travels through large respiratory droplets.

Close contact with an infected person, touching contaminated surfaces and then touching your face can lead to infection. The virus primarily affects the nasal passages but can spread to the lungs in severe cases, potentially causing pneumonia.

Preventive measures such as frequent handwashing, covering coughs and avoiding close contact with sick individuals are encouraged to limit its spread.

For mild cases, HMPV symptoms typically resolve within a few days to a week. More severe infections may take longer to improve and could leave lingering symptoms like a persistent cough.

There are no specific antibiotics to treat HMPV, so it’s encouraged to let the body fight it off on its own.

For mild cases, getting plenty of rest and drinking lots of fluids is usually enough. In more serious cases, people might need to go to the hospital for extra oxygen or help managing other health issues such as asthma or COPD.

Esper explained that the immune system is very important for getting better, and most people feel back to normal within three to five days.

“Your immune system, for the most part, is all you need,” he said. “You just need the time to weather the storm, and that's what we do from a treatment standpoint. A lot of the time, you don't need any medical treatment.”

The long-term effects of HMPV are still being studied, he mentioned.

While early-life RSV infections have been linked to asthma, there is currently no evidence of similar long-term complications from HMPV, Esper said. Most folks recover fully without lasting issues.

To reduce the risk of HMPV infection, it’s encouraged to follow these hygiene practices:

• Wash your hands frequently with soap and water.
• Cover your coughs and sneezes with a tissue or your elbow.
• Avoid close contact with people who are sick.

Wear a mask during peak respiratory virus seasons, if needed.

When asked if other countries such as the U.S could experience an outbreak similar to that in China, Esper expressed that HMPV outbreaks happen annually worldwide, especially in the U.S., and are generally comparable in severity to other respiratory virus seasons.

He pointed out that, like other viruses during the COVID-19 pandemic, HMPV could potentially evolve into more aggressive forms. Scientists are continuing to study and monitor the virus to understand these risks better.

“We certainly have seen, over the previous years, that sometimes when viruses resurge after the pandemic, they have been a little more aggressive,” he said. “Maybe because we didn't see them for a whole year, and our immune systems weren't trying to see the response.”

Although HMPV isn’t as widely known as RSV or the flu, it’s still a significant respiratory virus. Being aware of its symptoms, understanding who is most at risk and taking preventive measures can help people stay healthy and protect those around them.

Esper stressed that maintaining good hygiene practices through regular handwashing, covering coughs and masking when necessary are the best defense against respiratory viruses like HMPV.