Human metapneumovirus infection
Most infections occur in the winter and spring. Most children will have been exposed to this virus by age 5. Reinfections throughout life are possible, and infections occur in all age groups.
The human metapneumovirus can cause both upper and lower respiratory tract infections, and there are wide variations in clinical manifestations. On one end of the spectrum, patients have symptoms of the common cold. Patients with pneumonia may have severe infection and associated acute respiratory distress syndrome.
Children typically present with fever, cough, and rhinorrhea. Wheezing may be present. Rash may occur in some patients.
In adults, the symptoms of infection due to this organism are nonspecific, and similar symptoms may be seen due to infection with other respiratory viruses. Older patients with chronic cardiopulmonary disease who are infected with the human metapneumovirus are at increased risk of hospitalization.
Immunocompromised patients (especially following hematopoietic stem cell transplantation) are at increased risk of severe infection and respiratory failure due to this infection. In one review, patients who underwent hematopoietic stem cell transplantation and developed this infection presented with nonspecific symptoms including fever, cough, and nasal congestion.
Chest radiograph findings are nonspecific. Multilobar infiltrates and small pleural effusions may be seen.
Note: In 2022 and 2023, pediatric invasive group A streptococcal (iGAS) infections and noninvasive group A streptococcal infection cases have been associated with respiratory infections due to human metapneumovirus, among other viruses. Concurrent or preceding viral infections, including varicella (chickenpox), may increase risk for iGAS infection. Severe outcomes of iGAS infections include necrotizing fasciitis, streptococcal toxic shock syndrome, and death.
B97.81 – Human metapneumovirus as the cause of diseases classified elsewhere
416730002 – Human Metapneumovirus
Differential Diagnosis & Pitfalls
- Infection with other respiratory viruses including influenza and respiratory syncytial virus – Polymerase chain reaction (PCR) testing of nasopharyngeal swab or bronchoalveolar lavage specimens can be used to rapidly diagnose infections with many respiratory pathogens, including these viruses.
- Pneumonia due to bacterial, mycobacterial, or fungal pathogens – The chest radiograph of human metapneumovirus infection is typically nonspecific and cannot be used to differentiate this infection from infection by other pathogens (especially in immunocompromised patients). A variety of diagnostic modalities, including culture of sputum or lung biopsy, may be required to make the diagnosis in difficult cases.
- Pneumonia due to Pneumocystis jirovecii – Patients have dyspnea, hypoxia, and diffuse pulmonary infiltrates.
- Malignancy and vasculitides – More typically present with nodular pulmonary lesions, but in immunocompromised patients, viral pathogens can present with similar lesions.
- Drug-induced pneumonitis as seen with certain chemotherapeutics or other chemical exposures.