Human Metapneumovirus: Common yet Underdiagnosed

Hello. I am Dr Eileen Schneider, a medical epidemiologist in CDC's Division of Viral Diseases. I'm pleased to speak with you as part of the CDC Expert Commentary series on Medscape. Today I will talk about human metapneumovirus, an important cause of respiratory illness that affects many people every year.

In the United States each year, human metapneumovirus is associated with approximately 20,000 hospitalizations among children younger than 5 years.^[1] It can also severely affect older adults and immunocompromised patients. Most people have a metapneumovirus infection by the age of 5 years; however all ages are at risk for infection.^[1]

The clinical presentation is usually mild and can include such respiratory symptoms as cough, fever, and nasal congestion. The symptoms are often clinically indistinguishable from infection with other common respiratory viruses, such as flu and respiratory syncytial virus (RSV).^[2] Human metapneumovirus infection can also progress to the lower respiratory tract and result in bronchiolitis and pneumonia.

Human metapneumovirus was recently identified, in 2001, as an important cause of respiratory illness. However, some serologic evidence suggests that the virus has been widespread since at least 1958.^[2]Metapneumovirus can be detected throughout the year, but infections typically peak in the United States from late winter to early spring. Of note, metapneumovirus cocirculates with RSV and flu during the respiratory virus season, but metapneumovirus activity generally peaks later in the winter than RSV and flu.^[3]

Because human metapneumovirus is relatively new and not well described, healthcare professionals might not routinely test for it or even consider it in their differential diagnosis. But CDC recommends that clinicians consider metapneumovirus testing, along with flu, RSV, and other common respiratory viruses, especially in patients with severe respiratory illness.

Test results can help identify a possible etiologic pathogen and help guide available treatment.

The most sensitive method for human metapneumovirus diagnosis is to test respiratory specimens using polymerase chain reaction (PCR) assays. Examples of respiratory specimens include upper airway specimens (such as a nasopharyngeal swab, oropharyngeal swab, or nasal wash), and lower respiratory tract specimens (such as sputum, tracheal aspirate, and bronchoalveolar lavage). In patients with clinical or radiologic evidence of lower respiratory infection, a lower respiratory specimen should be tested.

Metapneumovirus is commonly included in commercial multipathogen PCR respiratory panels. Antigen detection assays are also available for diagnosing this infection. Healthcare providers can contact their state health departments for assistance with laboratory diagnostics or consultation.

There is currently no vaccine, and antiviral treatment is not recommended. You can help your patients reduce their risk for respiratory illnesses caused by metapneumovirus and other pathogens by reminding them to wash their hands often and practice good hygiene habits.

For additional information about human metapneumovirus, see a recent Medscape article that describes the first published summary of metapneumovirus testing data from CDC's National Respiratory and Enteric Virus Surveillance System. Also see a new CDC webpage on the clinical features of the virus.

Thank you for listening.

Web Resources

CDC Human Metapneumovirus Clinical Features