Human metapneumovirus (HMPV) can cause upper and lower respiratory disease in people of all ages, especially among young children, older adults, and people with weakened immune systems. Discovered in 2001, HMPV is in the Pneumoviridae family along with respiratory syncytial virus (RSV). Broader use of molecular diagnostic testing has increased identification and awareness of HMPV as an important cause of upper and lower respiratory infection.

What is human metapneumovirus?

Human metapneumovirus (hMPV) is a recently identified member of a family of viruses that also includes respiratory syncytial virus and parainfluenza virus. Although identified in 2001 by investigators from the Netherlands, data suggest this is a common virus that has been responsible for respiratory illnesses for at least 50 years worldwide. Human metapneumovirus can cause upper and lower respiratory tract infections in patients of all ages but respiratory illnesses most often occur in young children or older adults.

How is human metapneumovirus transmitted?

Spread of the virus is most likely to occur by direct or close contact with the respiratory secretions of infected persons or by contact with objects and surfaces contaminated by their secretions.

What are the symptoms of human metapneumovirus?

Most persons with hMPV infection have mild symptoms including cough, runny nose or nasal congestion, sore throat and fever. More severe illness, with wheezing, difficulty breathing, hoarseness, cough, pneumonia, and in adults, aggravation of asthma, also has been reported. In children younger than 1 year of age, the elderly and persons who have weak immune systems, hMPV can cause more serious respiratory illness.

When is human metapneumovirus most common?

It is most common in late winter and early spring in the United States, however, one summer outbreak of hMPV respiratory illnesses in residents and staff of a long-term care facility in the United States has been reported.

What is the incubation period for human metapneumovirus?

It is believed most persons who develop illness will do so three to five days after being exposed to this virus.

Is there immunity to human metapneumovirus?

Limited data suggests that reinfection with hMPV can occur. It is believed most children become infected early in life and adult infections represent persons becoming infected with hMPV again. Repeated infection appears to result in milder illness although serious disease is a risk for patients who are immunocompromised.

How is human metapneumovirus diagnosed?

Human metapneumovirus testing is not readily available. At this time, research laboratories and a limited number of commercial laboratories perform testing for this virus.

Can human metapneumovirus be treated?

Supportive treatment for patients varies with the severity of the illness but generally treatment consists of fever reducers, antihistamines, breathing treatments and other means of providing comfort to the patient until the illness resolves.

How can human metapneumovirus be prevented?

Control measures used for other respiratory illnesses should be emphasized: covering the mouth and nose with a tissue when coughing or sneezing, or, coughing or sneezing into the upper sleeve rather than the hands, prompt disposal of used tissues and proper handwashing.

Can any other species become infected?

Non-human primates can become infected with human metapneumovirus; humans are their likely source of infection.

HMPV is most likely spread from an infected person to others through

• secretions from coughing and sneezing
• close personal contact, such as touching or shaking hands
• touching objects or surfaces that have the viruses on them then touching the mouth, nose, or eyes

In the U.S., HMPV circulates in distinct annual seasons. HMPV circulation begins in winter and lasts until or through spring. HMPV, RSV, and influenza can circulate simultaneously during the respiratory virus season.

Symptoms commonly associated with HMPV include cough, fever, nasal congestion, and shortness of breath. Clinical symptoms of HMPV infection may progress to bronchitis or pneumonia and are similar to other viruses that cause upper and lower respiratory infections. The estimated incubation period is 3 to 6 days, and the median duration of illness can vary depending upon severity but is similar to other respiratory infections caused by viruses.

Infection with HMPV can be confirmed usually by

• direct detection of viral genome by polymerase chain reaction assays, and
• direct detection of viral antigens in respiratory secretions using immunofluorescence or enzyme immunoassay.

Treatment is supportive and includes fever reducers, antihistamines, hydration and supplemental oxygen if necessary.

Currently, there is no specific antiviral therapy to treat HMPV and no vaccine to prevent HMPV. Medical care is supportive. However, your patients can help prevent the spread of HMPV and other respiratory viruses by following these steps:

• Wash their hands often with soap and water for at least 20 seconds
• Avoid touching their eyes, nose, or mouth with unwashed hands.
• Avoid close contact with people who are sick.

Patients who have cold-like symptoms should

• cover their mouth and nose when coughing and sneezing
• wash their hands frequently and correctly (with soap and water for at least 20 seconds)
• avoid sharing their cups and eating utensils with others
• refrain from kissing others
• stay at home when they are sick

In addition, cleaning possible contaminated surfaces (such as doorknobs and shared toys) may potentially help stop the spread of HMPV.

Since HMPV is a recently recognized respiratory virus, healthcare professionals may not routinely consider or test for HMPV. However, healthcare professionals should consider HMPV testing during winter and spring, especially when HMPV is commonly circulating.