Human metapneumovirus: A newly emerging respiratory pathogen

Purpose of review: The present review focuses on the recent discovery, and clinical and epidemiological features of a virus associated with respiratory tract infections. Recent findings: In June 2001, researchers in The Netherlands reported the discovery of a virus associated with respiratory tract disease in infants and children. Genetic studies of this newly discovered viral pathogen revealed that it was a paramyxovirus. This virus is the first human pathogen in the Genus Metapneumovirus and was called human metapneumovirus (hMPV). hMPV may be a common respiratory virus. Seroepidemiologic studies in The Netherlands suggested that, by age 5 years, nearly all individuals have been exposed to hMPV. The results of several studies suggest that hMPV may account for about 10% of respiratory tract infections in which a common respiratory virus, such as respiratory syncytial virus, or influenza or parainfluenza viruses, could not be detected, hMPV has been detected in patients with either upper or lower respiratory tract disease, or both. Symptoms associated with hMPV include cough, dyspnea, wheeze, and hypoxia. This newly recognized pathogen has been detected in children and adults. Epidemiological findings suggest that it may circulate worldwide and may have a seasonal distribution. Summary: hMPV is a newly emerging respiratory pathogen and may be the cause of a significant proportion of both upper and lower respiratory tract infection in infants, children, and adults.