Human metapneumovirus can present as either upper respiratory tract infection or lower respiratory tract infection.

• Common symptoms of upper respiratory tract infection include cough, rhinorrhea, congestion, and sore throat.
• Lower respiratory tract infection symptoms include wheezing, fever, cough, dyspnea, hypoxia. More often, lower respiratory tract infections in children cause bronchiolitis, acute asthma exacerbations, croup, and pneumonia. This may necessitate hospital admission, depending on the severity of symptoms.
• In adults, HMPV can cause pneumonia, acute asthma exacerbations, and acute exacerbations in chronic obstructive pulmonary disease.
• Gastrointestinal symptoms such as diarrhea, nausea, and vomiting have also been noted. Abnormal tympanic membrane suggestive of acute otitis media can also occur. These symptoms can be quite severe in adults with comorbidities, age greater than 65 years old, and immunocompromised patients, including those with HIV, cancer, immunomodulatory therapy, and transplant recipients.[1][3][5][7][8][9]

Identification of HMPV does not require confirmatory testing but is based on a clinical diagnosis majority of the time. However, there are laboratory tests that can be utilized,

Most commonly, confirmation of infection by HMPV is done by reverse transcriptase-polymerase chain reaction (RT-PCR) from nasopharyngeal swabs.

Radiographic findings on a chest X-ray are typically nonspecific unless HMPV leads to the development of bronchiolitis or pneumonia. Findings include lobar infiltrates, peribronchial cuffing, hypermutation, or diffuse perihilar infiltrates. It is crucial to assess vital signs and to perform a thorough physical examination looking for signs of respiratory distress and hydration status in order to determine which supportive care measures are necessary.[1][7][9]

The primary mainstays of treatment are supportive measures. Anti-pyretic medications such as acetaminophen and ibuprofen are given for those patients with fever. If the patient appears dehydrated and cannot tolerate oral hydration, intravenous fluid hydration is indicated. Additionally, patients with HMPV may require supplemental oxygen support such as high flow nasal cannula or even mechanical ventilation in severe cases causing acute respiratory failure, especially in those patients who have pre-existing respiratory or cardiac illness as well as those who are immunocompromised. Most patients do undergo a full recovery. However, every patient with HMPV should be placed on droplet precautions to limit and prevent spread. There is no current vaccine available for HMPV. However, there have been various vaccines against different structures of HMPV that have been tested on non-human primates and rodents that appear promising, however, none have been tested on human volunteers.[1][3][8][10]

The differential diagnosis for symptoms resembling HMPV infection includes noninfectious causes such as acute asthma and acute, chronic obstructive pulmonary disease exacerbations. Bacterial infections causing pneumonia can demonstrate a similar clinical picture. Other viruses must also be considered, including coronaviruses, rhinovirus, adenovirus, parainfluenza virus, respiratory syncytial virus, and influenza A and B.[3][9]

Human metapneumovirus carries a good prognosis. It does require the clinician to be attuned to a patient’s underlying medical conditions as well as signs to determine the severity of infection, including dyspnea, hypoxia, and the use of accessory muscles. Typically, supportive care measures are sufficient, and patients undergo a full recovery. Reinfection can occur, demonstrating short-lived and incomplete immunity to HMPV.[1][3][9]

Within certain patient populations, HMPV can cause severe illness requiring hospitalization. Among those are patients who are immunocompromised or have a pre-existing cardiac or respiratory condition. These patients are more susceptible to developing acute respiratory failure requiring high flow oxygen support, with some patients even deteriorating enough to require mechanical ventilation. In these cases, patients need to be admitted to the intensive care unit for close monitoring.[1][8]

Instructions for wiping down surfaces at home are essential to disclose to patients and patients’ families. Appropriate hand washing is paramount, as well as droplet precautions.[1]

Further treatment options are under research for HMPV. A nucleoside analog called ribavirin is an antiviral drug approved for the treatment of a closely related virus called RSV (respiratory syncytial virus), which causes similar symptoms as HMPV. In patients diagnosed with HMPV, ribavirin combined with intravenous immunoglobulin suggests a possible benefit for the treatment option in premature infants and immunocompromised patients. In vitro studies have demonstrated antiviral activity by decreasing HMPV replication and, thus, pulmonary inflammation.

One clinical study did use oral and aerosolized ribavirin along with intravenous immunoglobulin in 9 immunocompromised patients with two patients undergoing successful treatment. This does demonstrate a possible option for therapy, but further research must be undertaken. However, both ribavirin and intravenous immunoglobulin are expensive. Additionally, ribavirin has a teratogenic effect. Aerosolized ribavirin given by a small particle aerosol generator would need to be administered under extreme caution by a licensed respiratory therapist who is not pregnant nor has plans to become pregnant.[3][8][10][11]

HMPV infection can lead to visits to the Emergency Department or a primary care physician’s office. An interprofessional team approach is an important component of disease prevention, recognition, and treatment. If the patient is stable for treatment as an outpatient, the doctor and nurse need to educate parents and patients on proper handwashing and the importance of wiping down surfaces with disinfectants at home. This is crucial when there are other members of the family at home, especially those who are susceptible to infections.

In the hospital setting, the nurse should ensure that the patient is under respiratory droplet precautions and placed in a separate part of the hospital, especially if being admitted in order to prevent transmission. The doctor, nurse, patient, the parents of the patient, or anyone involved in the direct care of the patient should wear a mask to cover their nose and mouth. They should also wash/sanitize their hands before entering and exiting the room. The doctor should also verify the patient’s medical history in order to determine illness severity, progression, and those who are at high risk.

While the workup of the patient is in progress, the nurse should alert the doctor regarding changes in vital signs and respiratory status. This helps identify the need for acute management for the patient, such as supplemental oxygen or mechanical ventilation. If needed, the pharmacist can help educate patients and parents that treatment is mainly supportive, and there are no pharmacological treatments available for HMPV. These measures enhance patient-centered care to improve outcomes and provide safety for the patient with HMPV as well as others.[1][8][10] [Level 5]