Human Metapneumovirus: An Important Cause of Respiratory Disease in Children and Adults.

Human metapneumovirus is a paramyxovirus that was discovered in 2001 in the Netherlands. Epidemiologic studies have shown it to be a major cause of acute respiratory tract disease in normal infants and children worldwide, with a seasonal occurrence and spectrum of clinical illness most similar to the closely related respiratory syncytial virus. The greatest prevalence of severe disease requiring hospitalization in otherwise healthy children appears to be in those aged between 6 and 12 months, older than the peak age of hospitalizations for respiratory syncytial virus. Human metapneumovirus is also a significant cause of acute respiratory disease in adults, particularly the elderly and those with comorbid conditions such as chronic obstructive pulmonary disease, asthma, and cancer. Because there is no rapid diagnostic assay, reverse transcriptase polymerase chain reaction is most widely used. Animal models have been developed, and candidate live-attenuated vaccines are in preclinical trials, offering the potential for future interventions in high-risk groups.