Human metapneumovirus (HMPV) is a common respiratory virus that causes cold-like symptoms in most people but can lead to more serious lung infections in young children, older adults, and those with weakened immune systems. It belongs to the Pneumoviridae family, the same family as RSV, and circulates every year with a season that typically runs from January through early June in the United States. Most people have been infected with HMPV at least once by age five, though reinfection throughout life is common.
How HMPV Spreads
HMPV spreads the same way most respiratory viruses do: through respiratory droplets from coughing and sneezing, direct contact like shaking hands, and touching contaminated surfaces. The virus can survive on hard, nonporous surfaces like countertops and metal for several hours, though it loses about 99% of its ability to cause infection after eight hours on metal. On porous materials like tissues and paper, it breaks down much faster, with only about 4% to 12% remaining viable after two to four hours. Fabric appears to inactivate the virus almost immediately.
These survival patterns are similar to RSV, and infection control measures for HMPV follow the same recommendations: regular handwashing, cleaning frequently touched surfaces, and avoiding close contact with sick individuals.
Incubation Period
After exposure, symptoms typically appear within about five days, though the incubation period can range from three to nine days based on documented cases. When the virus spreads within a household, the time between one person getting sick and the next person developing symptoms is a median of five days, with a range of three to seven days.
Symptoms in Children and Adults
HMPV symptoms look a lot like a bad cold or the flu, making it nearly impossible to tell apart from RSV or influenza based on symptoms alone. In a study of 54 children aged 5 to 13 with confirmed HMPV infection, cough was present in 98% of cases, nasal congestion in 81%, fever in 65%, and sore throat in 63%. About half of the children experienced wheezing, shortness of breath, or poor appetite.
Most infections stay in the upper respiratory tract and resolve on their own. But in some cases, the infection moves deeper into the lungs. Among the children in that study, 13% were diagnosed with pneumonia, 24% had asthma flare-ups, 19% developed middle ear infections, and 4% had bronchiolitis, an infection of the small airways that can make breathing difficult for young children.
In adults, HMPV typically causes milder illness, similar to a common cold. However, older adults and those with chronic lung conditions like COPD face a higher risk of complications including pneumonia. People with weakened immune systems, such as organ transplant recipients or those undergoing cancer treatment, are also at elevated risk for severe disease.
How HMPV Is Different From RSV and Flu
The short answer: it’s not reliably different based on symptoms. Research comparing HMPV, RSV, and rhinovirus infections in hospitalized children found no significant differences in symptoms, lab results, demographics, or treatment between the three viruses. The clinical presentation overlaps so heavily that a reliable diagnosis can only be made through lab testing.
The main practical difference is timing. RSV season typically peaks in the winter months, while HMPV peaks later, around late March. Before the COVID-19 pandemic, HMPV’s peak consistently lagged behind RSV’s by about 11 to 12 weeks. Since the pandemic, that gap has widened to roughly 19 weeks, with less overlap between the two seasons.
How It’s Diagnosed
HMPV is diagnosed through molecular testing, most commonly a technique called RT-PCR that detects the virus’s genetic material in nasal swabs or other respiratory samples. Many hospitals and clinics use multiplex respiratory panels that test for HMPV alongside flu, RSV, COVID-19, and other viruses simultaneously. A negative test doesn’t completely rule out HMPV, and results are interpreted alongside your symptoms and other findings like chest X-rays. Testing is not always performed for mild illness, since the result typically wouldn’t change how the infection is managed.
Treatment
There is no antiviral medication approved for HMPV. Treatment is supportive, meaning it focuses on managing symptoms while your body fights off the infection. For most people, that means rest, staying hydrated, and using over-the-counter medications to bring down fever and relieve congestion.
For severe cases, particularly in young children or older adults who develop pneumonia or significant breathing difficulty, hospitalization may be necessary. In those settings, treatment can include supplemental oxygen and other respiratory support. Children with underlying conditions like asthma may need additional breathing treatments during the illness.
Vaccine Development
No vaccine for HMPV is currently available, but candidates are in clinical trials. One of the furthest along is IVX-A12, a combination vaccine designed to protect against both RSV and HMPV. In a Phase IIa trial of 264 adults aged 60 to 85, the vaccine was well tolerated and successfully triggered immune responses against both viruses. This trial established that a combination RSV/HMPV vaccine is feasible, though further and larger trials are still needed before any vaccine could reach the market.
Who Is Most at Risk
HMPV can infect anyone, but the people most likely to develop severe illness fall into a few groups:
- Young children, especially those under five, who may not yet have built up immunity from prior infections
- Adults over 65, particularly those with chronic heart or lung disease
- People with weakened immune systems, including transplant recipients and those on immunosuppressive medications
- People with COPD or asthma, whose existing lung conditions can worsen significantly during infection
For otherwise healthy older children and adults, HMPV is typically a self-limiting illness that resolves within a week or two, similar to a common cold. The virus circulates widely every spring, and most infections go undiagnosed simply because they’re mild enough to manage at home.