Metapneumovirus infection
Metapneumovirus infection is caused by the human metapneumovirus (hMPV), a member of the paramyxovirus family. This respiratory infection is particularly prevalent among children, with 25 to 50 percent of children infected by the age of two and nearly all by the age of five. While most adult infections are mild or asymptomatic, those who are older or immunocompromised may experience serious respiratory issues. Symptoms typically include fever, cough, and runny nose, often accompanied by wheezing and febrile seizures in young children. In high-risk groups, such as individuals with chronic heart or lung diseases, the infection can lead to severe complications like pneumonia and heart failure. Diagnosis is primarily through molecular methods such as PCR, while treatment remains supportive, as no specific antiviral therapies exist. Preventive measures focus on good hygiene practices to minimize transmission, which can occur through contact with respiratory secretions or contaminated surfaces. Despite its global presence, no effective vaccine is currently available for hMPV.
Metapneumovirus infection
- ANATOMY OR SYSTEM AFFECTED: Respiratory system
- ALSO KNOWN AS: Human metapneumovirus infection
Definition
Metapneumovirus infection is a respiratory infection with the human metapneumovirus (hMPV). The virus infects between 25 and 50 percent of children by the age of two and virtually all children by aged five, but reinfection occurs throughout a person’s life. As a cause of serious pediatric respiratory infection, hMPV is exceeded only by influenza and respiratory syncytial virus (RSV). Most adult infections are asymptomatic or mild, but serious lower respiratory tract disease may result if the person is older or immunocompromised.
Causes
The virus hMPV is a single-stranded, negative-sense ribonucleic acid (RNA) virus and a member of the paramyxovirus family. It is closely related to respiratory syncytial virus (RSV) and avian pneumovirus (APV). Serologic studies have shown that hMPV has infected humans since the mid-twentieth century or earlier. While the origin of hMPV is uncertain, its similarities to APV suggest that it may have come from birds. The virus remained unidentified until 2001 because it causes nondistinctive respiratory disease and is very difficult to culture. hMPV is present worldwide, and infections are seen in the late winter and early spring in the Northern Hemisphere. The virus targets the bronchial epithelial cells. In fatal cases, diffuse alveolar damage occurs.
Risk Factors
Exacerbations of asthma may be seen when hMPV infects children younger than three years of age. Adults with chronic heart or lung diseases who become infected with hMPV are at risk of developing more severe respiratory disease requiring hospitalization. Outbreaks have occurred among the older residents of nursing homes. Persons with human immunodeficiency virus infection or who have had transplants and persons on chemotherapy often experience more severe infection; some transplant recipients have had organ rejection.
Symptoms
Fever, cough, and rhinorrhea are present in most children infected with hMPV after an incubation period of three to six days. Wheezing and febrile seizures are common. Acute otitis media accompanies the infection in more than one-half of the infected children three years of age and younger. In healthy adults, infection with hMPV is often asymptomatic but may cause an illness resembling influenza or the common cold. Adults with underlying cardiopulmonary disease may have worsening asthma or chronic obstructive pulmonary disease (COPD) or may develop pneumonia or heart failure as a consequence of infection. Immunocompromised persons can develop diffuse pneumonia accompanied by life-threatening respiratory failure.
Screening and Diagnosis
The most sensitive tests employ molecular methods with a variety of polymerase chain reaction (PCR) assays, such as real-time RT-PCR and multiplex PCR assays. Infection with hMPV may be identified in respiratory secretions using immunofluorescent antibody, which is only slightly less sensitive than the more complicated PCR methods. Viral culture may be used but has largely been replaced by faster and more sensitive molecular methods. Serology may be used, but seroconversion or a fourfold rise in antibody titer is necessary for the diagnosis of acute infection.
Treatment and Therapy
Treatment is supportive because no specific antiviral or antibody therapy is available for the infection.
Prevention and Outcomes
Handwashing and disinfection of contaminated surfaces and objects are the best forms of prevention, as transmission of hMPV is thought to occur through contact with infectious secretions, fomites (inanimate objects), and aerosols. Viral shedding may continue for between six and twenty-eight days. No effective vaccine is available.
Bibliography
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Falsey, Ann R. "Human Metapneumovirus." Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases, edited by Gerald L. Mandell, John F. Bennett, and Raphael Dolin. 7th ed., Churchill Livingstone/Elsevier, 2010.
"Human Metapneumovirus (HMPV)." Cleveland Clinic, 20 June 2023, my.clevelandclinic.org/health/diseases/22443-human-metapneumovirus-hmpv. Accessed 6 Nov. 2024.
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"Learn About Human Metapneumovirus (hMPV)." American Lung Association, 30 Oct. 2024, www.lung.org/lung-health-diseases/lung-disease-lookup/human-metapneumovirus-hmpv/learn-about-human-metapneumovirus-hmpv. Accessed 6 Nov. 2024.
Williams, John V. "The Clinical Presentation and Outcomes of Children Infected with Newly Identified Respiratory Tract Viruses." Infectious Disease Clinics of North America, vol. 19, 2005, pp. 569-584.