Human Metapneumovirus: What Is it and What Is Being Done About It?

While respiratory syncytial virus (RSV), influenza, and COVID-19 are respiratory viruses called the “triple pandemic” this winter, there may have been yet another culprit. Could some of the illnesses be human metapneumovirus (HMPV)? What does the data show? Infection Control Today^® (ICT^®) explains what HMPV is and whether it is necessary to differentiate it from similar illnesses.

“[HMPV] can cause upper respiratory infections, bronchitis, and pneumonia, just like influenza, RSV, COVID-19, and other viruses, Anne Meneghetti, MD, executive director of medical information at epocrates, told ICT. “It can occur in people of all ages, particularly in children, older adults, and people with weakened immune systems.”

Patients with a history of asthma, COPD, emphysema, or other lung disease are not more likely to contract the illness. However, once they have it, these lung diseases can worsen symptoms. Patients with weakened immune systems, undergoing chemotherapy, or being a post-organ transplant also can have more deleterious symptoms.

Although no conclusive studies have yet verified its transmission mode, “it is likely that transmission occurs by contact with contaminated secretions, via droplet, aerosol, or fomite vectors. Hospital-acquired infections with human metapneumovirus have been reported,” as noted in an NIH-published study.

Discovered in 2001 by scientists in the Netherlands, “Human Metapneumovirus is in the same family as RSV (respiratory syncytial virus); it’s been around for many years, yet the availability of new tests has led to increased diagnosis and awareness,” Meneghetti added.

While there is no particular antiviral therapy to treat HMPV and no vaccine to prevent HMPV, a clinical vaccine trial of combined HMPV and Parainfluenza Virus Type 3 was completed in December 2022. According to the CDC, supportive medical care should be given.

Meneghetti told ICT, “Common symptoms include cough, nasal congestion, and shortness of breath—these are similar to what we see with other viruses, so the symptoms alone don’t distinguish these viruses from another. While influenza is more common in the winter, this virus is more actively circulating in late winter and early spring.”

To make initial diagnosis more difficult, HMPV, influenza, and RSV can circulate concurrently during the respiratory virus season. Although data do not prove it, the incubation period is 3 to 6 days. The median duration of illness can vary depending upon the disease’s severity but is similar to other respiratory infections caused by viruses.

According to the American Lung Association, most children infected with HMPV are age 5 or younger. Between 5 to 16% of infected children will develop a lower respiratory tract infection such as pneumonia or bronchitis. Additionally, several outbreaks of HMPV have been reported in long-term care facilities for children and adults, including fatalities.

“Does knowing that one has metapneumovirus matter? There’s no specific treatment, so knowing whether or not someone has metapneumovirus isn’t typically a routine consideration,” Meneghetti said.” Prevention is the same as other respiratory viruses, including handwashing, covering one’s mouth and nose, and avoiding others while sick.”

The CDC does report positive tests reported throughout the United States here. The positivity rates vary widely from area to area, with the Western US census region showing the highest rates since August 2022.

According to the CDC, “In health care settings, providers should follow CDC’s 2007 Guideline for Isolation Precautions: Preventing Transmission of Infectious Agents in Healthcare Settings.”