RESPIRATORY TRACT infections are the most common illnesses worldwide, and viruses, including human metapneumovirus (hMPV), are responsible for many of these infections in both children and adults.1 hMPV outbreaks have been reported in behavioral health facilities, hospitals, and long-term-care facilities, and they impact both patients and healthcare personnel.2–4 The virus causes illness throughout the year, but peak activity occurs during winter and spring, nearly simultaneously with respiratory syncytial virus (RSV) infections and seasonal influenza.1,5
hMPV was first isolated in 2001 from 28 hospitalized children in the Netherlands with infections similar to RSV.6 Both RSV and hMPV share many epidemiologic and clinical characteristics.7 Humans are the only natural hMPV carriers.5
hMPV is transmitted from infected individuals via their saliva, droplets, and large particle aerosols when they talk, sneeze, or cough. The virus can also be transmitted through contact with contaminated objects and surfaces. The incubation period is 4 to 6 days, and the virus is shed from 5 to 14 days after inoculation.8 The duration of contagiousness is unknown.1 Infected adults who are asymptomatic may be an underappreciated source of transmission.1
Infants and young children infected with hMPV demonstrate signs and symptoms similar to RSV: cough, wheezing, myalgia, dyspnea, tachypnea, rhinorrhea, and pyrexia.8 In adults, signs and symptoms include nasal congestion, cough, rhinorrhea, hoarseness, wheezing, and dyspnea; fever is rare.8 Immunity after infection is short lived, and reinfection can occur in people of all ages.5 Older adults experience more recurrences due in part to a decline in their immune system functioning.9 Young adults have the highest incidence of infection.7
Most healthy older adults tolerate infection without serious complications. Older adults with cardiopulmonary disorders, such as chronic obstructive pulmonary disease (COPD), and patients who are immunocompromised are at greater risk for severe infection, resulting in hospitalization and possible death.
Patients may also become coinfected with other respiratory viruses such as RSV or seasonal influenza, and this may increase the severity of illness.6,7,10 hMPV infection may also lead to bacterial and fungal superinfections, including bacterial pneumonia.
Diagnosis and treatment
An hMPV diagnosis can't be made based on clinical signs and symptoms alone. Chest X-ray is abnormal in about half of patients with a lower respiratory tract infection.5 White blood cell count and C-reactive protein levels are typically normal during hMPV infection.5
The virus is difficult to culture using viral replication methods. Because hMPV is a virus, a routine bacterial culture won't detect this organism. Using reverse transcriptase polymerase chain reaction amplification techniques to detect viral RNA from nasopharyngeal aspirates or respiratory secretions is the most common testing method and will assist with the diagnosis.
Testing for hMPV will assist with the differential diagnosis of RSV, influenza, and other viral infections, bacterial infections such as Mycoplasma pneumoniae, Chlamydia pneumoniae, Bordatella pertussis, and noninfectious causes such as asthma and COPD.5 It can also be useful in respiratory outbreak situations with identifying a causative infectious agent.
Currently, no specific antiviral treatment exists for hMPV. Treatment is supportive to relieve signs and symptoms (acetaminophen, supplemental oxygen, hydration). Antibiotics are indicated only to treat a bacterial superinfection.
The CDC recommends contact precautions for the duration of the illness and wearing a surgical mask when examining a patient with signs and symptoms of a respiratory infection, particularly if he or she has a fever. Maintain isolation precautions until it's determined the patient doesn't have an infectious disease that requires droplet precautions or contact precautions.8,11,12
Researchers continue to work on developing an hMPV vaccine. Ensuring an effective and long-lasting immune response with vaccination remains a challenge. Animal studies have been conducted but no human studies have been performed.9 The CDC closely follows hMPV trending to assist with understanding the virus' infection burden and epidemiology.1
While awaiting diagnosis and after the hMPV diagnosis is confirmed, advise patients to:
- wear a mask when leaving their room.
- practice respiratory etiquette: cover the nose and mouth with a tissue, upper sleeve, or elbow when coughing or sneezing.
- avoid touching the eyes, nose, and mouth.
- avoid close contact with anyone who's sick.
- limit contact with other people while sick and avoid going out in public.
- implement best practices for hand hygiene.12
1. Haas LE, Thijsen SF, van Elden L, Heemstra KA. Human metapneumovirus in adults. Viruses
2. Cheng VC, Wu AK, Cheung CH, et al. Outbreak of human metapneumovirus infection in psychiatric inpatients: implications for directly observed use of alcohol hand rub in prevention of nosocomial outbreaks. J Hosp Infect
3. Degail MA, Hughes GJ, Maule C, et al. A human metapneumovirus outbreak at a community hospital in England, July to September 2010. Euro Surveill
. 2012;17(15). pii:20145.
4. Liao RS, Appelgate DM, Pelz RK. An outbreak of severe respiratory tract infection due to human metapneumovirus in a long-term care facility for the elderly in Oregon. J Clin Virol
5. Hermos CR, Vargas SO, McAdam AJ. Human metapneumovirus. Clin Lab Med
6. Falsey AR, Erdman D, Anderson LJ, Walsh EE. Human metapneumovirus infections in young and elderly adults. J Infect Dis
7. Mazzoncini JP Jr, Crowell CB, Kang CS.Human metapneumovirus: an emerging respiratory pathogen. J Emerg Med
9. Feuillet F, Lina B, Rosa-Calatrava M, Boivin G. Ten years of human metapneumovirus research. J Clin Virol
11. Siegel JD, Rhinehart E, Jackson M, Chiarello L Healthcare Infection Control Practices Advisory Committee. 2007 Guideline for Isolation Precautions: Preventing Transmission of Infectious Agents in Healthcare Settings. http://www.cdc.gov/ncidod/dhqp/pdf/isolation2007.pdf