Metapneumovirus

Human metapneumovirus (HMPV) is a member of the Pneumoviridae family of viruses, that includes respiratory syncytial virus (RSV). It is an RNA virus that was first discovered in the Netherlands in 2001. HMPV can cause upper and lower respiratory tract infections in people of all ages. In the United States, HMPV season usually begins in winter and extends through spring. Following RSV, HMPV is the second most common cause of acute respiratory illnesses in otherwise-healthy children under 5 years of age. Even though almost everyone has been infected with HMPV by 5 years of age, reinfections are common in older children and adults, because immunity wanes. 

Person to person transmission usually occurs by inhaling aerosols produced by an infected person’s coughing and sneezing. HPMV can also be contracted by close personal contact with an infected person or touching contaminated surfaces and fomites and then touching your mouth, nose, or eyes. Following infection, the Incubation period for hMPV is 3 to 6 days. Most patients experience mild upper respiratory symptoms similar to a cold. These symptoms include cough, runny nose, sore throat and fever. 

Children, older adults, and persons with compromised immune systems are at higher risk for hMPV-associated lower respiratory tract infections such as bronchitis, bronchiolitis, and pneumonia. hMPV can also exacerbate asthma and chronic obstructive pulmonary disease. Approximately 2% of adults hospitalized with HMPV have died. 

Due to the length of time required to detect HMPV, respiratory viral cultures are impractical for diagnostic purposes. Reverse transcriptase polymerase chain reaction (RT-PCR) is the most sensitive and commonly used method for diagnosis of HMPV infection. Collection of a respiratory specimen within 3 to 4 days after symptom onset can increase detection of respiratory viruses by molecular diagnostic tests. 

HMPV is also detected by the BioFire FilmArray Respiratory Panel. Specimen requirement is a nasopharyngeal swab, nasal wash or bronchoscopy specimen. 

Currently, there is no specific antiviral therapy to treat HMPV infections and no vaccine to prevent it. 

References

Williams JV, Harris PA, Tollefson SJ, et al. Human metapneumovirus and lower respiratory tract disease in otherwise healthy infants and children. N Engl J Med 2004;350:443–50.

Hamelin ME, Côté S, Laforge J, et al. Human metapneumovirus infection in adults with community-acquired pneumonia and exacerbation of chronic obstructive pulmonary disease. Clin Infect Dis 2005;41:498–502. 

Haynes AK, Fowlkes AL, Schneider E, Mutuc JD, Armstrong GL, Gerber SI. Human metapneumovirus circulation in the United States, 2008 to 2014. Pediatrics 2016;137:e20152927. 

Haas LE, Thijsen SF, van Elden L, Heemstra KA. Human metapneumovirus in adults. Viruses 2013;5:87–110.

Kahn J. Epidemiology of Human Metapneumovirus. Clin Micro Rev 2006;19:546-557.