It seems like every other week there is another virus or ominous-sounding acronym making headlines. This week, it's human metapneumovirus or hMPV.
Fortunately, hMPV is not a new pathogen. It's a pretty common respiratory virus in the United States — but if you've never heard of hMPV before, you aren't alone.
While the country's attention remained on COVID-19, influenza and respiratory syncytial virus or RSV, hMPV silently flew under the radar. The lesser-known respiratory virus has recently sparked conversation and concern online.
Cases of hMPV in the U.S. rose sharply between February and April this year, according to recent data from the U.S. Centers for Disease Control and Prevention.
The percentage of positive hMPV tests (averaged over three weeks) peaked in the U.S. during mid-March at about 19% for antigen tests and 11% for PCR tests, data show.
During the four years before the COVID-19 pandemic, the weekly percentage of positive hMPV tests peaked around 7% in March and April, per the CDC.
What do we know about hMPV so far, which symptoms can it cause, and is it serious? We spoke to experts to find out.
What is hMPV, aka human metapneumovirus?
It’s a common virus that causes illness in the upper and lower respiratory tracts, Dr. William Schaffner, a professor of infectious disease at the Vanderbilt University Medical Center, tells TODAY.com. It affects people of all ages but especially children, older adults and people with weakened immune systems.
"HMPV is one of many seasonal respiratory viruses, usually spiking in the late winter and spring," Dr. Thomas Murray, associate professor of pediatric infectious diseases at the Yale School of Medicine, tells TODAY.com.
The mid-March surge in cases captured by the latest CDC data is normal, he adds. As the virus follows its usual seasonal patterns, the CDC's three-week average percentage of positive hMPV tests has dropped significantly since April and remained low.
Is hMPV the same as RSV?
HMPV is in the same family as RSV, or respiratory syncytial virus, Awareness of the virus has increased in recent years as testing methods improved, per the CDC. A 2010 study of hMPV and RSV in kids found that hMPV causes similar symptoms to RSV and has a similar severity, but pediatric patients tend be older with hMPV than with RSV. The study added the hMPV is a major reason kids end up in the hospital.
According to Schaffner and the CDC, common hMPV symptoms include:
- Runny nose
- Sore throat
- Nasal congestion
- Shortness of breath
In some cases, an hMPV infection can progress to bronchitis or pneumonia, per the CDC.
Is human metapneumovirus just a cold?
There are more than 200 different types of viruses that can cause a common cold, which is usually just a mild infection in the upper respiratory tract, hence the feeling of a sore throat, runny nose, etc. Rhinoviruses are the most common virus that causes the common cold — not hMPV.
That said, the symptoms of hMPV are typically mild and very similar to the common cold, says Schaffner.
Is hMPV serious?
HMPV is typically mild, but it can cause serious illness leading to hospitalization or serious complications. When this does happen it's usually in infants or young children, the elderly, or people who are immunocompromised, Schaffner notes.
“It is one of many respiratory viruses (such as parainfluenza, adenovirus, rhinovirus) that make children sick (during winter), especially if they are very young or have an underlying medical problem,” says Murray.
However, the experts emphasize hMPV generally isn't a cause for concern. "Mostly, human metapneumovirus is troublesome but not terribly serious,” says Schaffner.
How long does hMPV last?
Symptoms of hMPV tend to last about three to seven days, according to Schaffner. The CDC says that the incubation period, or the amount of time between exposure and first symptoms, is three to six days.
There’s no vaccine or specific treatment for hMPV. “As with all of these common cold viruses, we can offer some symptomatic relief to get you through it,” says Schaffner. These include rest, hydration, over-the-counter medication and other home cold remedies, TODAY.com previously reported.
“Currently treatment is supportive care as for other common respiratory viruses, and in general the outcomes after infection for healthy children are excellent,” says Murray.
Is hMPV contagious?
Yes, hMPV is contagious and can spread through close contact.
How is human metapneumovirus transmitted?
HMPV is transmitted between people through close contact, respiratory droplets produced when an infected person coughs or sneezes, or contaminated surfaces, per the CDC.
People can prevent transmission of hMPV and other respiratory viruses by practicing frequent hand-washing, avoiding contact with sick individuals, staying home when sick, avoiding touching their face, and disinfecting shared surfaces.
Why did hMPV surge this spring?
“The CDC data is not necessarily unusual. ... The question is whether it is higher than previous years, which is difficult to (determine) since the pandemic dampened infection," Dr. Albert Ko, infectious disease physician and professor of public health, epidemiology and medicine at Yale School of Public Health, tells TODAY.com.
The experts note that technology and amount of testing for hMPV has also changed in recent years, which may affect numbers.
“There may be more hMPV being detected this spring because more testing for respiratory viruses is being performed now compared with prior to the COVID-19 pandemic," says Murray.
Adds Schaffner: "As technology advances, we can make diagnoses of these pesky respiratory viruses that plague us in the wintertime, and the more you look, the more you'll find."
The recent surge in hMPV, as well as other respiratory viruses like RSV, is likely a rebound after a period of decreased transmission during the pandemic, the experts note. "There was a diminution in the transmission of these respiratory viruses during the COVID era because we were wearing masks, being socially distant, and children were staying home from school," says Schaffner, adding that these behaviors gave the viruses less opportunity to spread.
Compared with previous years, this winter and spring people were increasingly mixing in person, traveling and returning to offices and schools — often without public health measures in place.
"These viruses have taken the opportunity to spread. ... That's what happened with the flu, what happened with RSV, and now with human metapneumovirus," says Schaffner.