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Human Metapneumovirus

Updated : June 21, 2024





Background

Human metapneumovirus (HMPV) is a viral pathogen that causes respiratory tract infections in people of all ages, particularly in children, the elderly, and those with weakened immune systems. This virus belongs to the Pneumoviridae family, primarily transmitted through respiratory droplets from infected individuals.

HMPV infections commonly occur during childhood, with the possibility of recurring infections throughout life. These infections often present as upper or lower respiratory tract infections, with lower respiratory tract infections being the most frequent. HMPV infections can lead to bronchiolitis, pneumonia, and acute asthma exacerbations, particularly in young children and immunocompromised individuals.

The primary treatment for HMPV infections is supportive care measures, such as supplemental oxygen, antipyretic agents, and hydration with intravenous fluids if necessary. In severe cases, hospitalization may be required to provide supportive care and monitoring.

Epidemiology

HMPV was first identified in 2001 in the Netherlands as a cause of respiratory symptoms in children. However, subsequent serological studies have shown that this virus has circulated in the Netherlands since at least 1958. HMPV infections can occur throughout the year, but the peak incidence in the northern hemisphere typically occurs in early spring and late winter. This virus is also found globally on all continents.

HMPV infections are common in children, especially those under the age of 2 years. Seroprevalence studies suggest that almost all children have been infected with HMPV by the time they are five to ten years old. In the pediatric population, HMPV is responsible for about 5% of hospitalizations due to acute lower respiratory tract infections. Children under six months with HMPV infection are at three times higher risk of hospitalization than children up to 5 years of age.

Re-infection with HMPV may appear due to diverse viral genotypes or poor immunity acquired from the initial infection. While adults usually experience mild flu-like symptoms, complications can occur in specific populations, such as the elderly, immunocompromised individuals, or chronic lung diseases. These complications can include pneumonia, exacerbation of underlying lung disease, and even death. Therefore, it is essential to take appropriate precautions to prevent the transmission of HMPV and to monitor high-risk individuals for potential complications.

Anatomy

Pathophysiology

HMPV spreads through respiratory droplets from person to person. It has an incubation period of three to five days, varying from person to person. Once the virus enters the nasopharyngeal mucosa, it rapidly enters the respiratory tract. HMPV has eight genes that code for nine different proteins, which enable it to infect host cells.

The attachment glycoprotein (G) and fusion glycoprotein (F) are crucial for HMPV’s entry into host cells. The fusion glycoprotein binds to integrins on the host cell’s surface, allowing the virus to fuse with the host cell’s membrane and enter it. Once inside the host cell’s cytoplasm, the viral nucleocapsid replicates, producing more viruses.

HMPV stimulates the production of various chemokines and cytokines, such as IL-2, IL-6, TNF-alpha, IFN-alpha, and macrophage inflammatory proteins. These proteins cause inflammation and perivascular and peribronchiolar infiltration. This inflammatory response also results in an influx of lymphocytes and monocytes in the airway endothelium. These responses together lead to pulmonary inflammation, resulting in symptoms such as cough, mucous production, fever, and dyspnea.

Etiology

In 2016, HMPV was reclassified from the Paramyxoviridae family to the Pneumoviridae family and the Metapneumovirus genus. It is a single-stranded, negative-sense non-segmented RNA virus enveloped in lipids. The primary mode of transmission is through respiratory droplets that contain the virus, which can easily infect susceptible individuals.

HMPV infections can range from mild to severe, with severe cases more commonly affecting individuals with compromised immune systems, pre-existing respiratory, neural, or heart disorders, and premature infants. The virus can cause respiratory symptoms such as cough, fever, and difficulty breathing, with more severe cases leading to pneumonia, bronchiolitis, and acute respiratory distress syndrome.

Genetics

Prognostic Factors

The prognosis for Human metapneumovirus has a good prognosis. However, it is important for clinicians to be aware of a patient’s underlying medical conditions and to monitor for signs of infection severity, such as dyspnea, hypoxia, and the use of accessory muscles.

Supportive care measures are typically enough, and most patients fully recover. However, reinfection is possible, which indicates that immunity to HMPV may be short-lived and incomplete.

Clinical History

Clinical History

The clinical history of a patient with human metapneumovirus varies widely depending on several factors, including the age and overall health of the patient, the severity of the infection, and any underlying medical conditions the patient may have.
HMPV is a respiratory virus that can cause various illnesses, from mild flu-like symptoms to severe respiratory distress.

HMPV infections are common in young children, older adults, and people with weakened immune systems. Common symptoms of HMPV infection include cough, congestion, runny nose, fever, shortness of breath and wheezing. In more severe cases, patients with HMPV infection may develop pneumonia or bronchiolitis, which can cause significant respiratory distress and require hospitalization.

In some cases, HMPV infection can also lead to more severe complications, such as secondary bacterial infections.
The clinical course of HMPV infection can vary from person to person. However, in general, symptoms typically appear within 3-5 days of exposure to the virus and can last up to several weeks.

Physical Examination

Physical History

The physical examination findings in a patient with HMPV may vary depending on the severity of the infection and the individual patient’s health status. A patient with HMPV infection may typically present with a fever, usually higher in children than adults. A dry cough, wheezing, rapid breathing, and nasal congestion with rhinorrhea are common symptoms.

On chest examination, crackles or rales may be heard on auscultation. Patients may also experience generalized weakness due to the body’s immune response to the virus. In some cases, HMPV infection may be accompanied by gastrointestinal symptoms such as nausea, diarrhea, and vomiting. An abnormal tympanic membrane, suggestive of acute otitis media, can also occur.

It’s important to note that these physical examination findings are not specific to HMPV alone and can overlap with other respiratory infections. However, for a definitive diagnosis of HMPV, laboratory testing of respiratory secretions is necessary. It is essential to test patients with comorbidities, ages greater than 65, and immunocompromised patients may experience more severe symptoms.

Age group

Associated comorbidity

Associated activity

Acuity of presentation

Differential Diagnoses

Differential Diagnoses

  • Chronic Obstructive Pulmonary Disease
  • Coronavirus
  • Respiratory Syncytial Virus
  • Parainfluenza Virus

Laboratory Studies

Imaging Studies

Procedures

Histologic Findings

Staging

Treatment Paradigm

Supportive measures are the primary treatment for patients with HMPV, including using antipyretic medications like ibuprofen and acetaminophen for fever control and intravenous fluid hydration for individuals who cannot tolerate oral fluids.

In cases where the patient appears dehydrated, supplemental oxygen support such as a high-flow nasal cannula or mechanical ventilation may be necessary, especially for those with pre-existing respiratory or cardiac illness or immunocompromised individuals who develop acute respiratory failure.

Although most patients recover fully, droplet precautions should be implemented for all patients with HMPV to limit and prevent its spread. Despite the absence of a vaccine for HMPV, several vaccines targeting different virus structures have shown promise in non-human primates and rodents. However, they have yet to be tested on human volunteers.

by Stage

by Modality

Chemotherapy

Radiation Therapy

Surgical Interventions

Hormone Therapy

Immunotherapy

Hyperthermia

Photodynamic Therapy

Stem Cell Transplant

Targeted Therapy

Palliative Care

Medication

 

ribavirin 

Off-label:

15 - 20

mg/kg

Orally 

divided 3 times a day

3 - 7

days


Note:
ribavirin should only be used under the supervision of a healthcare provider, as it can have potential side effects and may interact with other medications



 

ribavirin 

Off-label
For infants and young children:

6

mg/kg

every 12 hrs

3 - 7

days



 

Media Gallary

References

Human Metapneumovirus

Updated : June 21, 2024




Human metapneumovirus (HMPV) is a viral pathogen that causes respiratory tract infections in people of all ages, particularly in children, the elderly, and those with weakened immune systems. This virus belongs to the Pneumoviridae family, primarily transmitted through respiratory droplets from infected individuals.

HMPV infections commonly occur during childhood, with the possibility of recurring infections throughout life. These infections often present as upper or lower respiratory tract infections, with lower respiratory tract infections being the most frequent. HMPV infections can lead to bronchiolitis, pneumonia, and acute asthma exacerbations, particularly in young children and immunocompromised individuals.

The primary treatment for HMPV infections is supportive care measures, such as supplemental oxygen, antipyretic agents, and hydration with intravenous fluids if necessary. In severe cases, hospitalization may be required to provide supportive care and monitoring.

HMPV was first identified in 2001 in the Netherlands as a cause of respiratory symptoms in children. However, subsequent serological studies have shown that this virus has circulated in the Netherlands since at least 1958. HMPV infections can occur throughout the year, but the peak incidence in the northern hemisphere typically occurs in early spring and late winter. This virus is also found globally on all continents.

HMPV infections are common in children, especially those under the age of 2 years. Seroprevalence studies suggest that almost all children have been infected with HMPV by the time they are five to ten years old. In the pediatric population, HMPV is responsible for about 5% of hospitalizations due to acute lower respiratory tract infections. Children under six months with HMPV infection are at three times higher risk of hospitalization than children up to 5 years of age.

Re-infection with HMPV may appear due to diverse viral genotypes or poor immunity acquired from the initial infection. While adults usually experience mild flu-like symptoms, complications can occur in specific populations, such as the elderly, immunocompromised individuals, or chronic lung diseases. These complications can include pneumonia, exacerbation of underlying lung disease, and even death. Therefore, it is essential to take appropriate precautions to prevent the transmission of HMPV and to monitor high-risk individuals for potential complications.

HMPV spreads through respiratory droplets from person to person. It has an incubation period of three to five days, varying from person to person. Once the virus enters the nasopharyngeal mucosa, it rapidly enters the respiratory tract. HMPV has eight genes that code for nine different proteins, which enable it to infect host cells.

The attachment glycoprotein (G) and fusion glycoprotein (F) are crucial for HMPV’s entry into host cells. The fusion glycoprotein binds to integrins on the host cell’s surface, allowing the virus to fuse with the host cell’s membrane and enter it. Once inside the host cell’s cytoplasm, the viral nucleocapsid replicates, producing more viruses.

HMPV stimulates the production of various chemokines and cytokines, such as IL-2, IL-6, TNF-alpha, IFN-alpha, and macrophage inflammatory proteins. These proteins cause inflammation and perivascular and peribronchiolar infiltration. This inflammatory response also results in an influx of lymphocytes and monocytes in the airway endothelium. These responses together lead to pulmonary inflammation, resulting in symptoms such as cough, mucous production, fever, and dyspnea.

In 2016, HMPV was reclassified from the Paramyxoviridae family to the Pneumoviridae family and the Metapneumovirus genus. It is a single-stranded, negative-sense non-segmented RNA virus enveloped in lipids. The primary mode of transmission is through respiratory droplets that contain the virus, which can easily infect susceptible individuals.

HMPV infections can range from mild to severe, with severe cases more commonly affecting individuals with compromised immune systems, pre-existing respiratory, neural, or heart disorders, and premature infants. The virus can cause respiratory symptoms such as cough, fever, and difficulty breathing, with more severe cases leading to pneumonia, bronchiolitis, and acute respiratory distress syndrome.

The prognosis for Human metapneumovirus has a good prognosis. However, it is important for clinicians to be aware of a patient’s underlying medical conditions and to monitor for signs of infection severity, such as dyspnea, hypoxia, and the use of accessory muscles.

Supportive care measures are typically enough, and most patients fully recover. However, reinfection is possible, which indicates that immunity to HMPV may be short-lived and incomplete.

Clinical History

The clinical history of a patient with human metapneumovirus varies widely depending on several factors, including the age and overall health of the patient, the severity of the infection, and any underlying medical conditions the patient may have.
HMPV is a respiratory virus that can cause various illnesses, from mild flu-like symptoms to severe respiratory distress.

HMPV infections are common in young children, older adults, and people with weakened immune systems. Common symptoms of HMPV infection include cough, congestion, runny nose, fever, shortness of breath and wheezing. In more severe cases, patients with HMPV infection may develop pneumonia or bronchiolitis, which can cause significant respiratory distress and require hospitalization.

In some cases, HMPV infection can also lead to more severe complications, such as secondary bacterial infections.
The clinical course of HMPV infection can vary from person to person. However, in general, symptoms typically appear within 3-5 days of exposure to the virus and can last up to several weeks.

Physical History

The physical examination findings in a patient with HMPV may vary depending on the severity of the infection and the individual patient’s health status. A patient with HMPV infection may typically present with a fever, usually higher in children than adults. A dry cough, wheezing, rapid breathing, and nasal congestion with rhinorrhea are common symptoms.

On chest examination, crackles or rales may be heard on auscultation. Patients may also experience generalized weakness due to the body’s immune response to the virus. In some cases, HMPV infection may be accompanied by gastrointestinal symptoms such as nausea, diarrhea, and vomiting. An abnormal tympanic membrane, suggestive of acute otitis media, can also occur.

It’s important to note that these physical examination findings are not specific to HMPV alone and can overlap with other respiratory infections. However, for a definitive diagnosis of HMPV, laboratory testing of respiratory secretions is necessary. It is essential to test patients with comorbidities, ages greater than 65, and immunocompromised patients may experience more severe symptoms.

Differential Diagnoses

  • Chronic Obstructive Pulmonary Disease
  • Coronavirus
  • Respiratory Syncytial Virus
  • Parainfluenza Virus

Supportive measures are the primary treatment for patients with HMPV, including using antipyretic medications like ibuprofen and acetaminophen for fever control and intravenous fluid hydration for individuals who cannot tolerate oral fluids.

In cases where the patient appears dehydrated, supplemental oxygen support such as a high-flow nasal cannula or mechanical ventilation may be necessary, especially for those with pre-existing respiratory or cardiac illness or immunocompromised individuals who develop acute respiratory failure.

Although most patients recover fully, droplet precautions should be implemented for all patients with HMPV to limit and prevent its spread. Despite the absence of a vaccine for HMPV, several vaccines targeting different virus structures have shown promise in non-human primates and rodents. However, they have yet to be tested on human volunteers.

ribavirin 

Off-label:

15 - 20

mg/kg

Orally 

divided 3 times a day

3 - 7

days


Note:
ribavirin should only be used under the supervision of a healthcare provider, as it can have potential side effects and may interact with other medications



ribavirin 

Off-label
For infants and young children:

6

mg/kg

every 12 hrs

3 - 7

days