What to know about metapneumovirus—the respiratory infection you’ve never heard of that spiked this spring

You may have experienced human metapneumovirus—a (relatively) newly recognized “bug” hitting radars in a post-pandemic world.

Cases of the virus—discovered in 2001, and also known as HMPV—spiked this spring, peaking in May, according to data from the U.S. Centers for Disease Control and Prevention. They also spiked in more dramatic fashion in January, February, March, and April, contributing to a winter surge of respiratory viruses often referred to as the “tripledemic.” (The term, which acknowledged COVID, RSV, and the flu, failed to recognize other respiratory viruses like HMPV, rhinoviruses, enteroviruses, and parainfluenzas, which also contributed.)

HMPV is “probably much more common than we know,” Dr. Georges Benjamin, executive director of the American Public Health Association, tells Fortune. 

“We are finding it more often because we are testing people for respiratory diseases post-COVID and RSV,” he says.

Human metapneumovirus is a leading cause of acute respiratory infection, according to the American Lung Association. As with RSV, most humans have been infected with HMPV by age 5. While the vast majority will fare fine at home, as many as 10% of pediatric hospitalizations are due to lower respiratory infections caused by the virus, according to the National Library of Medicine. A 2010 study found that it was the one of the most common viruses among 256 children hospitalized with respiratory ailments, second only to RSV.

When it comes to elderly adults, about 22 in every 10,000 are hospitalized with the virus each year—particularly seniors with cardiovascular disease, according to a 2013 article in the journal Viruses.

Symptoms are pretty much identical to other respiratory viruses, and testing is necessary to tell them apart. As with its relative, RSV, HMPV has the potential to hit harder for the young and the elderly, as well as for those with weakened immune systems. 

Here’s what you need to know about the oft-undetected virus, known to spike each winter and spring.

What are the symptoms of metapneumovirus?

Symptoms are similar to other respiratory viruses, according to the CDC, and include:

• cough
• fever
• nasal congestion
• shortness of breath

In severe cases, symptoms may eventually progress to bronchitis and pneumonia.

Where did metapneumovirus come from?

It’s believed to have evolved from a virus in birds, and likely spilled over to humans about 200 years ago, according to a 2022 article in the medical journal Viruses.

How does metapneumovirus spread?

The virus spreads from person to person in the way most respiratory viruses do, including:

• coughing and sneezing
• close personal contact like shaking hands
• touching objects that have the virus on them, then touching your mouth, nose, or eyes

It usually takes three to six days to fall ill with the virus after being exposed.

How do I know if I have metapneumovirus?

Only a lab test can tell if you have the virus. In rare cases in which someone is hospitalized and suspected to have the virus, doctors might perform a bronchoscopy, during which a small, flexible camera collects fluid from the lungs, according to the American Lung Association.

Are there treatments for metapneumovirus?

There currently aren’t treatments, nor are there vaccines. If you have metapneumovirus, you’ll likely end up taking pain or fever relievers, resting, and staying hydrated. Your doctor may also recommend using a humidifier or taking a long, hot shower to ease sore throat and cough. In severe cases, hospitalized patients may require oxygen and fluids, according to Merck Manual, a popular reference for doctors and pharmacists.

How can I avoid metapneumovirus?

Tips for avoiding the virus are the same you’d follow to steer clear of other respiratory pathogens like cold, flu, and COVID. They include:

• Stay away from sick people.
• Wash your hands for at least 20 seconds.
• Avoid touching your face before washing your hands.
• Disinfect surfaces like doorknobs, countertops, and light switches regularly.

If you’re sick, stay home if you can, and cover your mouth and nose when you cough or sneeze.